Toward Sustainable Agricultural Systems in the 21st Century (2010)

One of the underlying themes of this report is the tension between the rapid specialization of much of U.S. agriculture in the last few decades and its resulting high production of individual commodities (Chapter 2) with the requirements of robustness, resilience, and appropriate levels of environmental integration in sustainable production systems (as discussed in Chapter 1). That tension revolves around the balance between the “industrial philosophy” and “agrarian philosophies” (Box 1-7) and varies among different commodities and environments. This chapter illustrates a few system types that lie within the complex matrix of that balance. They represent modifications within industrial approaches, and, in some cases, a more aggressive departure toward an agrarian approach. Chapters 3 and 4 highlight advances in the scientific understanding of different management practices and approaches that can contribute to improving productivity and environmental, economic, and social sustainability. The practices are central to the examples below because they are components of a larger farming system.

“System” is interpreted in a broad sense, from the individual farm agroecosystem to the wider ecological system or biome. The systems approach recognizes the importance of interconnections and functional relationships between different components of the farming system (for example, plants, soils, insects, fungi, animals, and water). It also stresses the significance of the linkages between farming components and other aspects of the environment and economy. Understanding how the components function individually and the outcomes each produces becomes the foundation of systems agriculture research. The aggregate outcome of applying those practices in concert cannot be predicted from simply combining the anticipated outcome of each practice because they interact with one another. In some instances, the combination of practices has complementary or synergistic relationships; in other instances, combining two practices might have unintended negative consequences.

A systems approach to agriculture is generally guided by an understanding of agroecology, as a scientific basis, and agroecosystem interactions. Agroecology applies ecological concepts and principles to the design and management of agricultural systems to im-

prove sustainability (Gliessman, 1998; Altieri, 2004; Wezel and Soldat, 2009). Agroecology provides a framework to integrate the biophysical sciences and ecology for management of agricultural systems. It emphasizes the interactions among all agroecosystem components (for example, biophysical, technical, and socioeconomic components of the farming system) and recognizes the complex dynamics of ecological processes (Vandermeer, 1995). The approach aims to maintain “a productive agriculture that sustains yields and optimizes the use of local resources while minimizing the negative environmental and socio-economic impacts of technologies” (Altieri, 2000).

When used in agriculture, agroecosystems have been defined as “communities of plants and animals interacting with their physical and chemical environments that have been modified by people to produce food, fiber, fuel, and other products for human consumption and processing” (Altieri, 1995). Agroecosystem design has been recognized as an important part of an agroecological approach, which is a more holistic concept of integrated resource management and understanding complex interactions than a reductionist approach (Swift et al., 1996).

This chapter uses a few farming system types to illustrate how they combine practices and to discuss the potential environmental, social, and economic outcomes. (See Box 2-1 for articulation of the distinction between “farming system”—the integrated system of a single farm management entity—and a “farming system type”—aggregations of farming systems defined by commonalities of commodity, management practices, or farming system approach.) Specifically, the organic, integrated crop–livestock, pasture-based livestock, low-confinement hogs, and perennial grains system types are used in this chapter to represent commonalities of commodity, of specific management approach to those commodities, or of a particular philosophical or scientific approach to farming system management. The integrative perspective of how the components interact with each other in a system and the study of the potential outcomes of those interactions provide valuable information for designing, implementing, and operating a farming system that achieves multiple sustainability goals. Beyond the boundary of a farm, many elements of sustainability, such as product and market diversity and resilience, water resource quality and use, elements of ecosystem health, and community well-being, are highly influenced at landscape, watershed, and regional scales. Sustainability, thus, suggests and requires in most instances an appropriate mix and location of farming system types. The last part of this chapter discusses agricultural sustainability at the landscape level.

The organic approach to farming, and specifically to cropping systems, is of scientific interest as an alternative type of system to the conventional type for several reasons:

• The organic approach is driven by a philosophy of using biological processes to achieve high soil quality, control pests, and provide favorable growing environments for productive crops, and by the prohibition of use of most synthetically produced inputs. For farm products to meet organic standards, farmers either substitute “organic” inputs (which are usually expensive) or use “biological structuring” (illustrated by use of practices described below) to achieve a high level of internal ecosystem services in their farming systems to permit high efficiency and productivity. Most productive organic farms are highly integrated and use what is referred to as a holistic approach to manage agricultural operations and their processes and impacts (Vandermeer, 1995; Gliessman, 1998; Altieri, 2004). (See the

discussion of “contending philosophies” in Box 1-7.) Organic farming systems represent an expression of the agrarian philosophy and can provide cost data for that position of the spectrum.

• There is an ongoing database of the numbers and types of certified organic farms, which features their production and marketing characteristics in the United States (USDA-ERS, 2009b; USDA-NASS, 2009) and on a global basis (Willer et al., 2008).

• Farmers have developed organic cropping systems for most major crop commodities and are located in nearly all major agricultural ecoregions of the United States (USDA-NASS, 2009).

• While they represent a small portion of total U.S. crop production, organic crop farmers had $1.1 billion in sales from 14,900 farms in 2007 (USDA-NASS, 2009).

As discussed in Chapter 1, many nonorganic farms lie somewhere between the conventional and organic continuum because they include some organic approaches and materials in their farming systems out of concern for the environment, human health, input costs, and other factors (for example, the Bragger Farm, Thompson Farm, and Green Cay Farm in Chapter 7). Yet, because much of the research literature is based on comparisons of a stylized organic farm versus a stylized conventional farm, many comparisons in this section can be considered assessing farms at opposite ends of the continuum. In selecting organic as an alternative example, the committee is in no way implying that U.S. agriculture should completely turn aside from modern, synthetically derived nutrients, pesticides, or pharmaceuticals. The example illustrates, however, the success that farmers have had with an ecological approach and the degree to which it can be environmentally and economically competitive.

Organic farming has evolved over many years since it started in Europe in the early part of the 20th century. Several “schools” of philosophy and practice are used to some extent today, as articulated in an extensive practitioner-written literature over the last 100 years (Harwood, 1990). The principles, in most cases, are consistent with scientific theory for ecosystem functioning (Drinkwater, 2009). Several guidelines for biodynamic systems are outside of present scientific theory. However, the majority of organic farms today are guided by either local or international certification requirements assembled through broad farmer and industry collaboration to regulate the rapidly growing marketplace for organic products. Some practices have been reasonably well researched, while studies on others are sparse. Products of some specialty approaches, such as biodynamic, have local or highly targeted niche markets. The following principles and practices, from popular organic literature, represent popular beliefs and values of practitioner-derived systems:

• Understanding and managing biological processes to regulate balance, flow, and timing of nutrient levels and availability; achieve pest-predator balance; and maintain healthy and productive crops and animals.

• Avoiding synthetic chemicals. Organic agriculture does not permit the use of synthetic chemical pesticides and fertilizers. An organic management approach needs to go beyond substitution of chemical inputs by approved organic inputs and needs to include the principles and practices explained here.

• Building healthy soil. Organic farming focuses on building healthy and fertile soil that has high microbial activity, is rich with beneficial and diverse microorganisms,

and is well-balanced in organic matter and humus. Good soil health is attained largely through cultural and biological management methods and use of natural organic inputs. Building and maintaining healthy soil is regarded as a key factor in maintaining plant health, which is thought to help avoid pest and disease problems by preventing crop stress or nutrient imbalance. Soil health is understood to be a basis for maintaining healthy balances of soil organisms in the farm (USDA-SARE, 2009). Nutrient cycling and regulation of the flows and temporal availability of nutrients to crops is a key goal of soil management.

• Managing biota within the system. Soil fauna are seen as critical to a healthy soil. Pest-predator balance within the soil and across the landscape is regarded as important to all systems, but is critical to many fruit and vegetable crops.

• Cycling nutrients. Organic agriculture aims to foster the cycling of nutrients and energy within and beyond the farming system. The cycling of energy and materials links the living organisms to the nonliving parts of the systems. Microorganisms cycle energy and chemicals from dead organic matter back into food chains (Lindeman, cited in Golley, 1993). Nutrient cycling is fostered in organic farms using various methods, including making and using compost, incorporating cover crops, and integrating crop residues.

• Conserving biodiversity and working with ecological processes and ecosystem functions. Organic farming aims to enhance biodiversity in and around the farm because it is believed that biodiversity can help maintain a balanced ecosystem. Organic farmers attempt to work with and enhance beneficial ecological processes and to take advantage of ecosystem functions. For example, farmers try to enhance ecosystem functions by planting diverse plants on the farm to attract beneficial insects.

• Adapting to local conditions to maintain balance. As in all farming systems, no uniform “prescriptions” for organic farming practices work for all farms. The methods are not standardized and have to be adjusted to local conditions. Crops need to be balanced with local growing conditions and ecosystem. Organic growers will likely change their practices over time as they learn innovations and as they adapt their methods to evolving environmental and economic conditions.

Many biophysical interactions are important to developing a fully integrated systems approach to organic farming. The intent is to analyze, manage, and enhance favorable interactions, rather than focus on specific technological responses or on input applications to solve problems. Those interactions are illustrated in Box 5-1, which is adapted from a guide used for vineyard management of a large organic grape grower in California.

In general, organic production systems produce lower yields than conventional production in developed countries. (See the case study on the Lundberg Family Farms in Chapter 7.) In meta-analysis studies comparing organic and conventional yields, Stanhill (1990) and Badgley et al. (2007) found organic yields per hectare to be 9 and 8 percent lower, respectively. Posner et al. (2008) found that organically managed corn in Wisconsin yielded 87 percent of corn produced in a traditional corn–soybean rotation; organic soybean yields reached 92 percent of their conventional counterpart. Similarly, organic corn in a Minnesota

study had yields 91 percent of those from a conventional two-year rotation, while corn produced with low levels of inputs only trailed the conventional yields by 3 percent. In a six-year study on cotton production in the San Joaquin Valley, California, Swezey et al. (2007) reported that cotton grown under organic management had consistently lower yield than under conventional management. Average yield over six years for cotton under organic management was 19 percent lower than for cotton under IPM and 34 percent lower than for conventional management.

Organic farmers commonly use cover crops, legumes, compost, animal and green manures, and animal byproducts (fish, bone, and blood meals) in their soil-building and nutrient management programs. In comparison studies with organic and conventional farming systems, scientists (Reganold et al., 1993, 2001; Mader et al., 2002; Pimental et al., 2005) have found organic farming systems to have better overall soil quality, as measured by soil properties such as more organic matter, better structure, less compaction, more earthworms, and greater microbial activity and diversity, than their conventional counterparts.

Organic farms often have smaller nutrient surpluses than do conventional farms (Kasperczyk and Knickel, 2006; Kustermann et al., 2010). Comparative studies on soil nutrient and water dynamics of organic and conventional farms usually show significantly lower leachable nitrates in organic systems (Stolze et al., 2000; Shepherd et al., 2003; Kramer

et al., 2006). The lower leachable nitrates in organic systems could be because they operate at lower levels of nitrogen application, and because nitrogen in organic systems is bound to organic fertilizers, such as composts and manures, when added or incorporated in the soil. Organically managed soils have been shown to store nitrogen more efficiently than their conventional counterparts (Clark et al., 1998). Other organic practices that minimize nitrogen losses are wide crop rotations, cover crops, and intercrops (Kasperczyk and Knickel, 2006). Although data on phosphorus loss from organic systems are limited, Lotter (2003) found phosphorus loss from leaching, runoff, and erosion in organic farming systems to be lower than in comparable conventional systems in all studies found.

The small nutrient surpluses in organic farms reduce the risk of nutrient (especially nitrogen) pollution from agriculture to rivers, lakes, wetlands, and coastal oceans. Han et al. (2009) reported that if farmers choose organic practices and reduce fertilizer use, nitrogen pollution levels could decrease to below present-day levels. They used existing data on nitrogen levels in rivers across 18 watersheds in the Lake Michigan basin and from five time intervals between 1974 and 1992. The researchers projected future nitrogen fluxes under three land-use and two climate scenarios: 1) business as usual, 2) increased dependence on organic farming, 3) increased fertilizer use from corn-based ethanol production, 4) a 5 percent increase in rainfall, and 5) a 10 percent increase in rainfall. The study revealed that the combined effect of 10 percent more rainfall and more ethanol production would increase nitrogen levels in rivers by 24 percent. However, increased use of organic farming practices could reduce nitrogen levels in rivers by 7 percent, even if rainfall increased by 10 percent. In southern Michigan, organic rotations using compost leached an average of 35 kg/ha of nitrogen per year compared to 53 kg/ha of nitrogen per year for conventional systems (Sanchez et al., 2004), a 34 percent reduction.

Weed control is one of the greatest challenges to yield productivity and economic profitability in organic systems. Seeding in organic grain systems is typically conducted later in the spring than in conventional systems to take advantage of the nitrogen in cover crops and to give weeds an opportunity to emerge. Soybean is particularly susceptible to weed competition. Cavigelli et al. (2008) showed that the yield difference between organic and conventional soybean in a Maryland experiment could be explained solely by the increased weed problem in the organic field. In a Wisconsin study, corn yields were 72 to 84 percent of conventional production in years with wet conditions (Posner et al., 2008). Soybean yields under the same conditions were 64 to 79 percent of yields for the conventional crops. However, in years where weather conditions were favorable and weed pressure was low, yields from organic and low-input systems were comparable (Porter et al., 2003; Posner et al., 2008).

Organic farms tend to rely on hand labor for weed control more heavily than do conventional farms. In a survey of 59 tomato farms in Indiana, Hillger et al. (2006) found that farmers generally reported more hours of hand weeding for fields under organic management than for those under nonorganic management. Swezey et al. (2007) found that production cost of cotton grown under organic management is higher than nonorganic management primarily because of the greater hand-weeding costs and lower productivity. Although improvements have been made in tillage machinery for controlling weeds in organic systems, results from research and experience suggest that additional research is needed in economical weed control for those systems. (See also Chapter 3.)

Organic crop production could have lower greenhouse-gas emissions than conventional production because the former does not use synthetic fertilizers or pesticides that require fossil fuel to produce. Meisterling et al. (2009) conducted a lifecycle assessment to compare the global warming potential and primary energy of conventional and organic wheat production. Their model estimated that the global warming potential of producing 0.67 kg (for a 1 kg loaf of bread) of wheat is 190 g of carbon dioxide equivalent (CO₂eq) using conventional production and 160 g CO₂eq using organic production. Those modeled estimates, however, include high uncertainties associated with N₂O emitted from fields and soil carbon sequestration because excess nitrogen input can increase N₂O emission in either conventional or organic production. Nitrous oxide release is correlated more with overall soil nitrogen levels and mineralization amounts than with source of nitrogen input. Loss of soil carbon and N₂O emissions can be reduced by using best management practices in either conventional or organic production (Meisterling et al., 2009). In a long-term ecological research experiment in Michigan, organic treatments were found to have nitrous oxide (N₂O) greenhouse warming similar to conventional no-till, low-input rotation with legumes and perennial alfalfa in spite of having no fertilizer N input (Robertson et al., 2000). (See also Table 3-1 in Chapter 3.) Net greenhouse warming potential for the organic system was less than half that of standard conventional with full tillage, but higher than for no-till due to the higher soil carbon gains from no-till. Systematic assessment of greenhouse-gas emissions of different cropping systems or system types over the lifecycle of crop production is sparse.

The economics of organic cropping systems has considerable variation by regions of the United States and by different crops. Organic crop yields per acre are generally lower and labor requirements are often higher than in conventional agriculture systems. However, purchased input costs are less than conventional agriculture so that profits per acre are typically only slightly lower than conventional agriculture. Most organic farmers gain price premiums that range from 5 percent to more than 70 percent of the market price obtained by conventional products (Greene et al., 2009; USDA-ERS, 2009b). Fruits and vegetables account for more than 37 percent of organic food sales, which include processed products. The profits per acre of organic farming can significantly exceed those of conventional agriculture.

The most accurate comparisons between organic and conventional agriculture are seen across crop rotations rather than between specific crops. Moreover, organic agriculture is often a favorable alternative in regions where farmers lack access to synthetic inputs because of the inability to purchase inputs or absolute lack of physical access to inputs, or in regions with a large labor supply (as in many developing countries).

In a long-term farming systems trial at the Rodale Institute in Pennsylvania, the net returns per acre for the conventional system were slightly higher than the net returns per acre for the organic system without premiums during the period of 1991 to 2001 (Pimental et al., 2005). Production costs per acre for the organic system were lower. Total labor for the organic system was higher, but because it was spread more equally through the growing season, the organic system had fewer off-farm hired workers. Organic corn production over the 10-year period was more profitable per acre than conventional corn, but organic corn was not grown as often in the rotation because of the need for soil-building crops. When all land, cover crops, and input costs were calculated, given the frequency of each crop in

the rotation, production costs per unit of output were 10 percent higher for organic corn, soybean, wheat, and hay. Delate et al. (2003), however, found net returns for corn within the organic corn–soybean–oat and corn–soybean–oat–alfalfa rotations were significantly greater than conventional corn–soybean rotation returns on the basis of the market prices for the year of study.

Lotter (2003) reviewed numerous comparisons of organic versus conventional agriculture in the United States and worldwide. He concluded that despite the lower yields of organic crops compared to conventional crops, organic systems can still be more profitable than conventional systems because of lower input costs and organic price premiums. When organic premiums were not included, conventional systems were generally more profitable. However, Welsh (1999) noted that the differences within a given system (for example, organic versus organic, conventional versus conventional) were often greater than the differences between the two systems and that the local environment had a greater effect on their relative performance. More specifically, Mahoney et al. (2004) found that the direct production costs for corn in a conventional two-year rotation were $60 per hectare more than corn produced in a two-year or four-year low-input rotation and $96 per hectare more than that of a four-year organic rotation. In soybean, the organic or low-input systems had a slight advantage of $13–$18 per hectare in savings over conventional production. The use of petroleum-based chemicals make nonorganic agriculture more vulnerable to the volatility of crude oil prices compared to organic agriculture (Scialabba, 2007).

Organic practices tend to be more labor intensive (Klepper et al., 1977; Pimental et al., 2005) and often need more intensive management time (Porter et al., 2003) than conventional agriculture. In general, unpaid family members provide a larger proportion of the overall farm labor (Tegegne et al., 2001; Macombe, 2007; MacRae et al., 2007). As a result, the economic performance of organic farming systems can depend heavily on the input costs attributed to unpaid family labor (Hanson et al., 1997; Brumfield et al., 2000). For example, a comparison of wheat farmers in the Mid-Atlantic found that organic farms were more efficient than conventional farms by $34/ha in terms of cash operating expenses. However, when opportunity costs, including unpaid family labor, were incorporated, the fortunes were reversed—organic costs exceeded those of conventional by almost $100/ha (Berardi, 1978). Organic farmers in this study also averaged four more hours of labor per hectare than their conventional colleagues.

In fruit and vegetable farms, an organic system with 50 percent organic premiums was more profitable than the conventional or integrated apple production systems (Reganold et al., 2001). For all three systems to break even (when cumulative net returns equal cumulative costs) at the same time, price premiums of 12 percent for the organic system and 2 percent for the integrated system would be necessary to match the conventional system. Walsh et al. (2008) noted that for organic apple production in the humid Mid-Atlantic, the organic price premium required to break even with the conventional production system was greater than the premiums currently offered by the market. Brumfield et al. (2000) reported that organic sweet corn was 2 percent more profitable than conventionally grown sweet corn in New Jersey. Economic analyses of organic production of California specialty crops also have shown higher profitability than conventional counterparts (Klonsky and Tourte, 1998).

The rapid rise in consumer demand for organic products and the concomitant growth of the organic market have brought important economic opportunities and benefits to producers, as discussed in Chapter 6. However, the ability of farmers to gain access to and advantages from the growing organic market depends partly on their marketing strategies and their location because of considerable regional variations.

Several economic analysts have also addressed questions about the scale of organic production. It is often argued that organic production is more conducive and successful for small- or medium-scale operations because organic farming usually requires more intensive management and labor requirements per unit of land, and because of biophysical aspects, such as difficulties in maintaining high levels of biodiversity at larger scales (Hall and Mogyorody, 2001). However, recent studies and prominent organic farming businesses, including several case studies in this report, show that large-scale organic farming systems can also be economically profitable and successful (for example, the Lundberg Family Farms and Stahlbush Island Farms described in Chapter 7). Indeed, by 2007 the average gross sales on U.S. organic farms (and degree of market concentration) were similar to farm sales by size category among conventional farms (USDA-NASS, 2009). Those sales data demonstrate clearly that most organic systems with their high levels of biological structuring through crop rotation, use of cover crops, IPM, and other commonly used organic practices can be applied across the full spectrum of scales if farmer monitoring and management systems are adequate.

Most published literature and policy discussions about the treatment of farm labor in sustainable farming systems have focused on the example of organic farming. Formal standards for organic food production, however, do not typically include detailed requirements for treatment or compensation of the farm labor force (IFOAM, 2002; Guthman, 2004; USDA-AMS, 2009).

Some explanations for why organic farms might have progressive farm labor practices and workplace conditions (Duram, 2005) include: organic farmers typically use fewer risky agrichemicals, are more likely to use diversified livestock and cropping systems that are better able to employ labor throughout the year, and might be more likely to share an ideological commitment to environmental and social justice issues (Pretty, 1995; Guthman, 2004; Glenna and Jussaume, 2007). Nevertheless, organic farming systems in the United States have been criticized for relying heavily on mundane hand labor and for exploiting the labor of idealistic, young farm interns seeking to learn about farming by working on organic farms for a summer. In addition, the organic and sustainable farming social “movements” have spent much more time advocating for environmental issues than for the well-being and fair treatment of farmers or farm workers (Allen et al., 1991; Allen and Sachs, 1993).

Detailed empirical studies of the labor practices on organic and sustainable farms have only recently been conducted. In general, organic production entails greater use of labor per unit output, although there is a greater share of overall farm labor obtained from unpaid family members (Tegegne et al., 2001; Macombe, 2007; MacRae et al., 2007).

Although the labor required to produce individual crops using organic techniques might be high, the diverse cropping patterns (and the reintegration of livestock into traditional cropping systems) often associated with organic farming can spread labor demands evenly throughout the year (Nguyen and Haynes, 1995). In some cases, the distribution of labor-input needs over time reduces the need for hired workers or could provide greater opportunities for full-time permanent employment for farm workers.

Perceived high labor requirements are often cited as a critical barrier to adopting organic methods by conventional farmers (Schneeberger et al., 2002). But, at the same time, the increased labor associated with alternative farming practices has not diminished the

work satisfaction of farmers or the likelihood of farm succession among farmers in France (Macombe, 2007). To some extent, machinery or management techniques can be developed or adapted to reduce labor needs in organic systems to levels similar to conventional practices (Peruzzi et al., 2007); a small fraction of public and private sector agricultural research and development has been conducted with that goal in mind (Dabbert et al., 2004).

Because of the large scale and heavy use of labor in Californian agriculture, several recent studies report data on the treatment of hired workers among organic farms in that state. Initially, Guthman (2004) reported that exclusively organic farms tended to pay higher wages to farm workers than farms that maintained both organic and nonorganic operations. However, larger farms of both types tended to pay higher wages and were more likely to offer benefits than small operations. Whether larger farms of either type tend to offer higher wages than their smaller counterparts was unclear.

An exploratory survey (Shreck et al., 2006) found that two-thirds of organic farmers in the survey hired workers (other than family members) for at least part of the year, but that just one-third of organic farms provided at least one basic health benefit to their workers. The provision of health insurance benefits was positively correlated with the overall scale of the farming operation. In addition, another study that compared wage and benefit practices of organic and conventional farms in California found that organic farms paid better wages and were more likely to offer profit-sharing (or produce-sharing) arrangements with their workers (Strochlic et al., 2008). However, conventional farms were more likely to offer their workers health insurance, paid time off, retirement plans, and employee manuals. Fair labor practices are not necessarily a result of organic farming. Whether farmers provide fair wages and good working conditions depends on their commitment to social justice, their perceived financial impacts on the farm as a result of such provision, and other conditions.

As discussed in Chapter 4, food security depends on multiple factors, including policies, prices, and access to food, but the first step is to ensure adequate production. Badgley et al. (2007) compiled data from multiple studies and estimated the global organic food supply by multiplying the amount of food in the 2001 food supply by a ratio comparing average organic to nonorganic yields. The authors suggested that organic farming could produce enough food on a global per capita basis to sustain the current human population, and potentially an even larger population, without increasing the agricultural land base. Their findings were based on a global dataset of 293 yield ratios for plant and animal production taken from previous studies that compare organic and nonorganic production systems (Badgley et al., 2007) and have been criticized by Cassman (2007). Although 74 percent of the studies used in the Badgley et al. dataset were from peer-reviewed journals (Badgley and Perfecto, 2007), Cassman (2007) stated that many studies “seem to be demonstrations and informal trials” and fail to meet reliable scientific standards. Another criticism is that a portion of their dataset was from Pretty and Hine’s (2000) survey data from 52 developing countries, where many farms included as “organic” were only “close to organic.” Nevertheless, their results, along with the Stanhill study (1990) mentioned earlier, suggest that organic methods of food production can contribute to feeding the current and future human population on the current agricultural land base.

Crop yields in organic and nonorganic systems were also discussed earlier in the context of farm economics. This committee did not consider whether a certain system type could feed the world because how each system type is managed can affect the farm’s sus-

tainability performance. Doran et al. (2007) argued that “[a] focus on existing conventional and emerging organic systems limits the possibilities.” They suggested that “the emphasis should be on developing cropping systems that best contribute to a set of well-defined performance parameters that ensure adequate food supply and farm family income, treats farm labor well and farm animals humanely, and protects environmental quality and natural resources” (Doran et al., 2007, p. 78).

Although consumers often perceive organic fruits and vegetables as more nutritious than their conventional counterparts, the nutritional superiority of organic crops has not been unequivocally demonstrated. Such comparisons are often complicated by the interactive effects on nutritional quality of farming practices, soil quality, climate, plant genetics, and the time of harvest (Benbrook, 2005; Benbrook et al., 2008), which account for the inconsistent differences reported in more than 150 studies that compare nutritional content of organic and conventional crops (Woese et al., 1997; Benbrook, 2005).

Benbrook et al. (2008) identified peer-reviewed studies that compare nutrient levels in organic and conventional foods published in the scientific literature from 1980 to 2007. Mindful of the confounding factors discussed above, they reviewed the articles to identify scientifically valid “matched pairs” of measurements that include an organic and a conventional sample of a given food. For each matched pair, they also made sure that the same cultivars were planted in both the organic and conventional fields, and the differences in soil types and topography were minimized. They took into consideration the focus and location of the study to only include pairs that use analytical methods for nutrient analyses that they considered reliable. They identified 236 matched pairs across 11 nutrients. The organic product had higher nutrient content than the conventional in 61 percent of the cases; the opposite was true in 37 percent of the cases. No significant differences in nutrient content were observed in 2 percent of the cases. They concluded that organic plant-based food, on average, is more nutritious than nonorganic food (Benbrook et al., 2008).

A controlled, replicated plot study conducted on a 1.7-hectare plot within a 20-hectare commercial orchard in Washington compared the productivity and fruit quality of apples under organic and conventional production (Peck et al., 2006). That study found that organic apples had a higher level of total antioxidant activity than similar-sized conventional apples. The researchers of the study asked panels of consumers to do taste-testing, and the panels tended to rate organic apples to have equal or better overall acceptability, firmness, and texture than conventional apples.

Another study compared the influence of organic and conventional crop management practices on the flavonoid content in a tomato cultivar (Lycopersicon esculentum L. cv. Halley 3155) over 10 years (Mitchell et al., 2007). That study observed higher levels of three flavonoids in tomatoes grown in the organic system than in the conventional system. Chassy et al. (2006) did a similar comparison of flavonoids and ascorbic acid in organic and conventionally managed tomatoes and bell peppers over a three-year period. They used two varieties of tomatoes (Lycopersicon esculentum L. cv. Ropreco and Burbank) and two varieties of bell peppers (Capsicum annum L. cv. California Wonder and Excalibur). They found that, unlike in tomatoes, flavonoid and ascorbic acid contents in bell peppers were not much affected by cropping systems. They suggested that different crops respond differently to agronomic and environmental pressures, so statements about organic crops having greater nutritional content than conventional crops are overgeneralized. Pieper and Barrett (2009) confirmed Chassy et al.’s suggestion when they compared the quality and

nutritional content of one variety of processing tomatoes (Lycopersicon esculentum var. AB2) produced under organic and conventional production systems on a commercial scale. Their study included data from three different growers for two production years. They found that nutritional quality of the one variety of processing tomato varied by growers and production systems. However, organically grown tomatoes in their study had significantly higher average soluble solids content and consistency than conventionally grown tomatoes.

As discussed in Chapter 4, one of the standards for evaluating the sustainability of a farming system type is whether the farms of that type have positive effects on the economic security of their local communities. Until the late 1990s organic agriculture was primarily oriented toward local and regional (mostly direct) sales and therefore contributed to the economic security of local communities. In 2004, 24 percent of organic sales were made locally and another 30 percent were made regionally (USDA-ERS, 2009a). Many Community Supported Agriculture (CSA) operations, for instance, are organic. Local, direct marketing to provide fresh produce to community markets is still a hallmark of a large segment of organic producers and remains one of the points of controversy among organic producers. With the enactment by the U.S. Department of Agriculture (USDA) of organic certification standards, large-scale production operations have became more common and marketing channels lengthened. The 2007 U.S. Census of Agriculture (USDA-NASS, 2009) lists 2673 crop farms (of the total 18,211 organic farms) that have sales of $50,000 or more per year, accounting for $1.02 billion in sales (of the total organic sales of $1.7 billion). Some see the trend towards larger organic farms as “an industrialization of organic production,” but that trend is observed across agriculture as a whole.

Increased species richness and abundance and continuous blocks of woodland are thought to improve aesthetics of the community. It has been inferred that organic farming enhances biodiversity because it prohibits the use of synthetic agrichemicals. Several studies in Europe attempted to compare biodiversity in conventional and organic farms. One study relied on meta-analysis (Bengtsson et al., 2005) and found that organic farming seems to have positive effects on species richness and abundance. Its effects, however, vary between organism groups and across landscapes. Gibson et al. (2007) found organic farms had greater total areas of semi-natural habitat (woodland, field margins, and hedgerows combined) than conventional farms in the southwest of England. The organic farms they studied had more continuous blocks of woodland (with simpler perimeters than similarly sized patches on conventional farms), whereas woodland on conventional farms often consisted of more linear patches. Although a larger percentage of semi-natural habitat appears to occur in organic rather than conventional farms, the study did not explore the cause of that association.

Over the past 50 years, the most striking changes in the U.S. livestock sector reflect the increasing use of production systems in which animals are kept in full confinement and are fed fewer traditional forage crops and higher proportions of corn, soybean, and food processing byproducts (MacDonald and McBride, 2009). Nevertheless, the last 30 years have also witnessed growing interest in a number of alternative livestock production systems. The alternative systems include efforts to expand the integration of crop and livestock enterprises, intensive grazing management systems on dairy farms, and low-confinement

integrated hog production practices. All three alternative systems take advantage of opportunities for greater on-farm cycling of nutrients, seek to mimic natural patterns of animal behavior, and respond to dissatisfaction by farmers and consumers with aspects of confinement livestock production systems.

Conventional economic wisdom suggests that specialized production systems have strong economic rewards. Specifically, scale economies (driven by new technologies, capital, and labor efficiencies) and commodity support policies have been linked to increasing farm specialization and a dramatic reduction in the average number of crops on typical farms, as well as the farm-level and regional-level separation of crop and livestock production enterprises (Hallam, 1993; Gardner, 2005; MacDonald and McBride, 2009). Economic challenges associated with diversification include higher management, labor, capital, and machinery requirements (Hendrickson et al., 2008; Wilkins, 2008).

Large specialized livestock facilities focus more on producing animals and purchase more of their livestock feed from off the farm than farming systems with both livestock and crops. That trend has led to a decline in available land for recycling livestock waste through cropping enterprises. Gollehon et al. (2001) reported a 40 percent decrease in available farmland per animal unit on U.S. farms from 1982 to 1997. The tendency for specialized livestock operations to purchase a higher percentage of their livestock feed requirements has led to growing imbalances in the supply of nutrients in livestock manure relative to the crop nutrient requirements in fields surrounding livestock operations at the farm, watershed, and regional levels (Kellogg et al., 2000; Ribaudo et al., 2003). At the same time, most U.S. cropland is managed as farms that do not use manures as an important source of nutrients. The 2007 Census of Agriculture reported that just 22 million acres of U.S. farmland received manure in 2007, less than 10 percent of the acreage that received chemical fertilizer treatments (USDA-NASS, 2009). That situation has led to serious waste disposal and water pollution issues around intensive livestock production, high use of fertilizer to replace the lost nutrients in land where animal feed crops are produced, and a 50 percent increase in global reactive nitrogen between 1890 and 1990 (Galloway and Cowling, 2002).

Evidence is increasing that integration of livestock into diverse cropping systems can produce important benefits (Sulc and Tracy, 2007). In particular, the ability to feed crops to livestock enables producers to capture and potentially recycle nutrients back to farm fields, which reduces the need for purchased fertilizers and enhances such desirable soil attributes as organic matter, water-holding capacity, and soil structure (Schiere et al., 2002; Entz et al., 2005; Hendrickson et al., 2007). Moreover, the ability of livestock to take advantage of underutilized resources (for example, less productive croplands that can be converted to pasture, periods of slack family labor demand, or unused crop residues) can improve the overall efficiency of the farm operation and capture new sources of income (Smil, 1999; Russelle et al., 2007). Livestock are often used to convert relatively low-value crops to high-value protein, which can potentially increase total farm returns on integrated crop–livestock farms (Anderson and Schatz, 2003).

Numerous studies have documented the economic benefits of integrated crop–livestock systems. Sulc and Tracy (2007) reviewed recent scientific studies of integrated crop–livestock farms in the U.S. Corn Belt, including the use of alfalfa in crop rotations, the use of annual or short-season pastures in rotation with grains, and the strategic grazing of crop residues. They reported that many of those systems have been shown to be economically competitive and offer environmental benefits when compared to specialized

production systems typical of that region. Marois et al. (2002) found that adding cattle and forage rotations into traditional cotton–peanut production systems in the Southeastern United States produced increased whole-farm returns. A similar study contrasting cotton–forage–beef systems with traditional High Plains cotton monoculture systems found that the integrated system reduced irrigation water needs by 23 percent, reduced nitrogen fertilizer applications by 40 percent, and increased net farm profitability by up to 90 percent on a per-acre basis (Allen et al., 2005, 2008). Other studies revealed significant economic advantages of integrated beef–crop operations (Anderson and Schatz, 2003; Gamble et al., 2005; Franzluebbers and Stuedemann, 2008).

Integrated crop–livestock systems have been found to be particularly beneficial when conservation tillage practices are used (Franzluebbers and Stuedemann, 2008). The use of short-term and long-term pasture crops in rotations and the strategic placement of well-adapted forage crops on the landscape can provide particular environmental and economic benefits (Entz et al., 2002; Rotz et al., 2005; Russelle et al., 2007). At the same time, most evidence for successful crop and livestock integration has been linked to the use of ruminant livestock (beef, dairy, sheep, or goats) that can eat forages and crop residues; different challenges exist for finding productive synergies for monogastric livestock species such as poultry and hogs.

Grazing systems encompass a diverse set of management strategies. Extensive low intensity pastoralist grazing systems have been prominent features of human society for millennia, and the bulk of the U.S. beef cow and sheep flock inventory continues to spend a considerable amount of their lives grazing on rangelands, pastures, and the residues of harvested crop fields. More recently, interest has surged in more intensive grazing management systems, particularly so-called “management-intensive rotational grazing” (MIRG). A key feature of most MIRG systems is the use of short-duration grazing episodes on relatively small paddocks, with longer rest periods that allow plants to recover and regrow before another grazing episode.

MIRG approaches have quickly emerged as a major alternative production system among dairy farms in the Upper Midwest and Northeast, the nation’s “traditional dairy belt,” characterized by humid temperate climates and the persistence of mixed crop–livestock farming operations. Many farms in those regions use hybrid systems that combine MIRG during grazing months and conventional confinement production in the winter (Kleinman and Soder, 2008). Surveys suggest that MIRG operations constitute more than 20 percent of dairy farms and produce more than 10 percent of milk in major dairy states such as Wisconsin, Pennsylvania, New York, and Vermont (USDA-REEIS, 2003; Winsten and Petrucci, 2003; Taylor and Foltz, 2006). The use of MIRG-like systems is also becoming more common among beef producers in the Great Plains and Southeast. Studies have documented social and economic benefits to farmers from the use of MIRG dairy production systems, including comparable or greater profitability per cow or unit milk output, and higher quality of life and greater levels of satisfaction for farm operators. (See Mariola et al., 2005, and Taylor and Foltz, 2006, for recent reviews.)

Early reports and farmer testimonials suggested the potential for the adoption of MIRG systems to improve environmental sustainability, including improved soil quality, reduced

soil erosion, decreased input use, improved wildlife habitat, and potential for better sequestration of atmospheric carbon. Over the past 15 years, a considerable scientific literature has emerged to closely examine those claims (Mariola et al., 2005; McDowell, 2008; Taylor and Neary, 2008).

Scientific studies of conventional, extensive, or traditional pastoral grazing systems vastly outnumber studies of the more intensive forms of short-duration rotational grazing. Furthermore, many more studies focus on grazing in arid grassland or rangeland regions than on the temperate regions dominated by more productive cool-season grasses and forages. In both instances, it has become clear that livestock left in single grazed pastures for weeks or months at a time (continuous grazing) can generate overgrazed, sparse pastures with low persistence, diminished soil quality, and greater risk of soil erosion (Brummer and Moore, 2000; Teague and Dowhower, 2003). However, most MIRG systems are carefully monitored to manage intensity and timing of grazing to ensure continual ground cover and high-quality, high-yielding forage for livestock (Kanneganti and Kaffka, 1995; Paine et al., 1999; Hensler et al., 2007) without significantly diminishing ecosystem qualities.

The sections below provide scientific evidence regarding the impacts of grazing systems on soil quality, soil erosion, nutrient dynamics, greenhouse-gas emissions, biodiversity, and human health and nutrition. The committee found from its review of the literature that simple conclusions regarding an overall assessment of the environmental impacts of such systems cannot be drawn because environmental impacts depend heavily on at least three major factors: 1) local biophysical conditions, including climate, topography, and soil types; 2) the specific management practices used, including stocking rates, duration of grazing and rest periods, use of purchased fertilizers, and access to riparian areas; and 3) the types of “alternative” land uses against which the performance of grazing systems is compared.

In general, when compared to more intensively cropped fields, soils under pasture management tend to accumulate soil organic matter (SOM), which favors the development of good soil structure (Soane, 1990; Tisdall, 1994; Kemp and Michalkand, 2005). In a series of paired comparisons, rotationally grazed pastures have been shown to have significantly more SOM in the top 12 inches of soil than conventional row crop fields (Dorsey, 1998) or extensively grazed or hayed pastures (Conant et al., 2003). In well-managed pastures, high SOM was associated with higher rates of soil biological activity than equivalent arable fields (Cuttle, 2008). Earthworm populations were 1.3 to 3.0 times higher in MIRG fields than cropped fields (Dorsey, 1998; Mele and Carter, 1999). Improved soil structure in MIRG pastures has been associated with reduced soil erosion and nutrient runoff compared to tilled corn fields (DeVore, 2001; Haan et al., 2006).

However, poor management of grazing fields, particularly in wet conditions and under high stocking rates, can lead to soil compaction and hoof print indentations or pocketing in the top 12 cm of soil, which can diminish soil quality, decrease water infiltration, and increase the potential for soil erosion and runoff of sediment, nutrients, and fecal matter (Evans, 1997; Greenwood and McKenzie, 2001; Cuttle, 2008). Compared to natural or forested landscapes, most grazing systems have greater potential for runoff of nutrients, agrichemicals, and fecal microbes, and for deterioration of aquatic stream ecosystems. Overgrazing, in particular, can lead to defoliation, exposure of the soil surface to direct rainfall impacts, reduced root density, and shifts in plant communities that diminish soil quality and increase soil erosion (Schacht and Reece, 2008). Because they often allow for increased livestock numbers per area of land, MIRG systems require higher levels of management to avoid deleterious impacts on soil compaction and to maintain sufficient vegetative cover.

Management of riparian areas is critical to controlling impacts of grazing on aquatic ecosystems (Wilcock et al., 2008). Allowing access by livestock to streams or stream banks can cause decreased riparian area vegetative cover (particularly tall trees), increase stream bank erosion, decrease channel stability and channel width, and increase stream water temperatures. Morphological changes in stream conditions linked to runoff from grazing landscapes and degraded riparian areas typically reduce the ability of aquatic systems to support healthy fish and macroinvertebrate populations (Allan and Johnson, 1997; Allan et al., 1997; Rutherford et al., 1999; Wilcock et al., 1999; Wilcock and Nagels, 2001).

MIRG systems have been touted as environmentally friendly because a greater percentage of the farm’s land use is comprised of untilled permanent or semi-permanent pastures and hayfields, because they typically use much lower levels of artificial fertilizers and agrichemicals (Pain and Jarvis, 1999; Kriegl and McNair, 2005), use less fossil fuels and equipment, and offer direct opportunities to recycle nutrients between livestock and farm fields (Taylor and Neary, 2008). In particular, when compared to row crop farming and extensive grazing systems, there is evidence that well-managed intensive grazing systems can sequester more atmospheric carbon and minimize losses of agricultural nutrients to surface and ground waters (Cuttle, 2008).

Scientific studies of rising global concentrations of greenhouse gases have identified grassland ecosystems as potentially important sinks for sequestering atmospheric carbon (Kucharik et al., 2003; Lal, 2006; Allard et al., 2007). Soils store a large proportion of the world’s carbon (Amundson, 2001) such that small changes in soil carbon content can have a large effect on global carbon cycling. Studies of the conversion of tilled soils into native perennial grasses under the Conservation Reserve Program (CRP) suggest net increases in soil carbon (Reeder et al., 1998; Potter et al., 1999; Baer et al., 2000). In the Southeastern United States, pastures under MIRG management sequestered more soil carbon than continuously grazed or hayed fields (Conant et al., 2003). Net gains in soil carbon are highest in the first years of conversion from arable to untilled grasslands (Tyson et al., 1990). At a global scale, however, increased soil respiration as a result of global warming suggests that the world’s grasslands could be experiencing net losses of carbon (Bellamy et al., 2005; Schipper et al., 2007).

On the other hand, grazing livestock have also been identified as a significant potential source of greenhouse-gas emissions (de Klein and Eckard, 2008). Worldwide, pastoral grazing sources are estimated to contribute roughly 8 percent of methane (CH₄) and 15 to 30 percent of total N₂O emissions (Clark et al., 2005). Methane emissions are primarily a function of the fermentation of feed in the rumens of grazing animals, mostly lost through the lungs, not flatulence (Torrent and Johnson, 1994). By contrast, CH₄ losses from animal excreta are trivial sources of net emissions.

Methane emissions are affected by feed and forage type and by the intensity of grazing management. One study shows that grain-finished cattle that spend some time in feedlots produce more CH₄ emissions from enteric fermentation per animal than grass-finished cattle. However, because of their efficient weight gain, grain-finished cattle produce 38 percent less CH₄ emission per unit beef produced than grass-fed cattle. Higher-quality forages, including legumes, also tend to yield less CH₄ in the rumen (Peters et al., 2010). Intensive grazing can decrease CH₄ per unit weight gain, but greater rates of forage production and consumption could increase total CH₄ emissions per hectare. Nitrous oxide emissions in grazing systems are primarily a byproduct of the denitrification process in soils. Important sources of nitrogen deposition in pastures are livestock urine, commercial fertilizers, and legume crops. Denitrification is accelerated under wet or anaerobic conditions, which can

be aggravated by soil compaction and poaching in pastures (de Klein et al., 2001; Bolan et al., 2004). Emissions of both of types of greenhouse gases tend to increase with more productive pastures or intensive pasture management systems, because of higher soil nitrogen levels, rates of plant growth, and stocking rates.

MIRG farms experience different nutrient-cycling dynamics than traditional row crop and confinement agricultural systems. Although overall applications of nutrients to fields tend to be low in MIRG farms, a greater percentage of nutrients come from direct deposition by grazing animals (and less from commercial fertilizers) in intensive grazing systems. In general, lower levels of input use on MIRG farms provide fewer available nutrients (and much lower levels of pesticides and herbicides) than comparable row crop operations, therefore reducing the risks of losses to the environment. At the same time, deposition of manure and urine by grazing animals can be uneven, and areas of animal congregation (such as at watering troughs, feeding stations, under shade trees, and in overwintering fields) can become potential sites of nutrient build up. Field studies have reported mixed results on the impact of MIRG on nutrient cycling. Dorsey (1998) found that deep soil nitrate concentrations were significantly lower on MIRG fields than on low-intensity grazing or cropped fields. However, Stout et al. (1997) observed high nitrate losses underneath urine patches, which could contribute to ground water contamination at a field scale. Moreover, nitrate losses from grazing animals can be highly variable depending on rainfall patterns and levels of supplemental nitrogen fertilization (Stout et al., 2000).

Some have argued that MIRG systems offer environmental advantages over modern confinement livestock production systems that rely on harvested forage and grains as feed inputs and might have a sufficient land base on which to distribute livestock manure nutrients. Comparisons of intensive grazing and confinement livestock systems have produced mixed results. The mixed results reflect different assumptions about stocking rates, grazing practices, manure nutrient handling, and crop fertility management practices. Recent models for whole-farm nutrient budgets and a full accounting of farm-level nitrogen balances reveal little systematic difference between grazing and confined dairy operations (Rotz et al., 2002; Watson et al., 2002; Kleinman and Soder, 2008). Similarly, phosphorus-accounting models suggest that grazing operations are faced with similar challenges to effectively use phosphorus from animal manures on their fields as conventional confinement farms are (Sharpley, 1985; McDowell et al., 2007; Sharpley and West, 2008), partly because most confinement dairies in the United States still maintain active cropping operations. Whole-farming-system analyses of the risks of soil erosion, nutrient losses, and atmospheric greenhouse-gas emissions would account for losses within the livestock operations itself and in cropping farms and feed processing facilities that produce substantial portions of the feed inputs on many confinement farms.

There can be a tradeoff between managing farming systems to minimize nitrate (NO₃^–) losses to ground water resources or to reduce the loss of N₂O to the atmosphere. Many management practices designed to maximize denitrification efficiencies can reduce the threat of nitrate leaching (which benefits water quality), but can increase nitrous oxide emissions (which are potent atmospheric greenhouse gases). Using an intensive grazing system (particularly if it replaces reliance on traditional crop production for livestock feeds) could affect the balance between nitrate leaching into water and N₂O release into the atmosphere. For example, evidence suggests that denitrification efficiency under MIRG systems is higher than under a corn crop (70 to 90 percent versus 10 to 15 percent), in part due to subsurface soil environments that are richer in plant, microbial, and macrobiotic activities (Browne and Turyk, 2007). As a result, grazing farms contribute comparatively fewer nitrates to ground water, but might convert a higher percentage of nitrates and nitrites into N₂O and N₂ gases.

Ultimately, patterns of nutrient flows in pastures are affected by the impacts of grazing on soil structure, water infiltration, and soil microbial activity, as summarized above, and those interactions make it difficult to draw sweeping conclusions about the net environmental costs and benefits of grazing systems.

Compared to most arable farming systems, pastures and grazed rangelands tend to have more diverse plant, insect, and animal populations. Research on MIRG farms has focused on the impacts of greater use of managed pastures on wildlife and bird species. Higher proportions of the land base on MIRG farms offer potentially suitable habitat for grassland bird species (Paine et al., 1995; Temple et al., 1999). However, bird counts suggest that grazed pastures have similar levels of overall bird species richness, dominance, and density compared to crop fields, but higher levels of rare and unusual species in the Upper Midwest (Renfrew and Ribic, 2001). The role of management appears to be critical—efforts to exclude livestock from some pasture areas during nesting season are important to generating wildlife benefits (Holechek et al., 1982; Koper and Schimiegelow, 2006). Impacts of grazing systems on aquatic ecosystems was discussed elsewhere, but studies show that well-managed MIRG systems (particularly control over livestock access to riparian areas) can generate favorable conditions for fish populations (Mosely et al., 1998; Lyons et al., 2000).

At the landscape scale, grazing systems can provide important habitat diversity to watersheds dominated by traditional row crop and hay production (Nassauer, 2008). However, different grazing management strategies are likely to produce distinctive impacts on the composition of plant communities at the field and landscape scale (Schacht and Reece, 2008). Well-managed rangeland grazing systems have been associated with greater spatial and temporal variability in species richness (Bakker, 1994; Patten and Ellis, 1995; Fuhlendorf and Smeins, 1999). Continuous grazing and overstocking on rangelands or pastures can result in the elimination of plant species that are preferred by grazing livestock and an evolution toward lower-quality and less palatable species. Conversely, intensive short-duration grazing systems (like MIRG) force livestock to eat a diversity of plants, although the systems are still likely to select for species that can survive under this form of grazing pressure. Impacts of intensive grazing on biodiversity are also likely to differ depending on rainfall conditions, which affect the ability of plants to recover from grazing episodes.

Kriegl and Frank (2004) compared MIRG with traditional confinement (TC) systems (50 to 75 cows) in a stanchion barn with stored feed and family labor and with large modern confinement (LMC) systems that have more than 250 cows, milk cows in parlors and house cows in free stalls, and rely on hired help and stored feed. Their analysis was based on eight years of data. Table 5-1 summarizes 2002, the most recent year in their analysis. MIRG produced less milk per cow. However, MIRG’s expenses were lower so that its cost per hundred-weight of milk produced was lower. Net farm income per hundred-weight of milk produced was higher for dairy farmers using MIRG and continued to be even when all labor charges (which were higher for LMC) were omitted. However, income per farm was lower for MIRG, compared to LMC, because MIRG systems had fewer cows and lower milk yields per cow. Similar patterns have been found in other studies (Rust et al., 1995; Hanson et al., 1998; Dartt et al., 1999; Conneman et al., 2000; Winsten et al., 2000; Gloy et al., 2002; Kriegl and McNair, 2005).

The scale of operation associated with confinement and MIRG dairy systems appears to be different. In general, confinement systems—particularly modern parlor or freestall

confinement systems—have larger herds than rotational grazing operations. While their economic costs of production per unit output might not be notably lower, larger herd sizes enable confinement systems to generate greater gross income than intensive grazing systems as implemented in different regions of the country (Winsten et al., 2000; Kriegl and McNair, 2005). Smaller dairy operations might be better adapted for rotational grazing compared to larger operations, either because of management and logistical complexity, or because of the life style and income preferences of typical MIRG dairy farmers. Similarly, farmers who rely on traditional extensive pasture grazing practices have been disinclined to shift to more intensive rotational grazing techniques primarily because of perceived increases in labor and management required (Gillespie et al., 2008).

Dairy farmers who use management-intensive rotational grazing emphasize that the approach allows them to spread their labor more evenly throughout the day and the growing season, enables their young children to participate in more farming activities, and gives them a better appreciation for nature and the environment (Ostrom and Jackson-Smith, 2000; Brock and Barham, 2009). However, not all sustainable farming practices necessarily confer improvements in the quality of the labor experience. Beef ranchers, for example, are more likely to prefer extensive grazing approaches than a MIRG system because of the higher total labor (and labor per cow) associated with a more intensive management regime (Gillespie et al., 2008). Many MIRG approaches to sustainable farming require significant investments (Nichols and Knoblauch, 1996) in time and learning by the farm operator.

Although most operators of grazing livestock farms and ranches are drawn to grass-based systems for personal, social and economic reasons (Nichols and Knoblauch, 1996), a number of consumers are attracted to grass-raised meat products for perceived health benefits. In an extensive review of the scientific literature, Clancy (2006) found that meat products from pasture-raised cattle are associated with lower levels of total fat than meat from conventionally grain-finished animals. Similarly, meat and milk from pasture-raised animals has been shown to contain higher levels of particular kinds of fats (Martz et al.,

1997; Dhiman et al., 1999; Beaulieu, 2000; White et al., 2001). Specifically, ground beef from grass-fed cattle contains higher levels of conjugated linoleic acid (CLA), and milk from pasture-raised cows contains higher levels of both CLA and alpha-linolenic acid (ALA, an omega-3 fatty acid). CLA has been linked to reduced risk of heart disease and heart attacks, and omega-3 acids have been linked to the same benefits, plus potential reduced risks of cancer and immune system diseases.

Hog production (in the United States and globally) has undergone sweeping changes in the last 30 years. The number of U.S. farms with hogs declined from 667,000 in 1980 to 75,442 in 2007, but the total animal inventory increased slightly from 62.3 to 67.8 million (Informa Economics, 2004; USDA-ERS, 2008). Of the total farms with hogs in 2007, 84 percent had less than 1,000 animals each and accounted for 2.3 percent of animals sold. The 2,850 operations with over 5,000 animals made up 3 percent of hog operations and accounted for 87 percent of hogs sold in 2007. Along with the dramatic change in size has come a significant shift in production practices and in facilities. The most important distinctions in type of operation are between confinement operations that are not integrated (except for manure disposal) with crop operations and operations that are highly integrated with crop production. Operations of each type can be classified by the U.S. Environmental Protection Agency as concentrated animal feeding operations (CAFOs), depending on size and methods of manure disposal. The distinction among alternatives, and the wide network of support farm-integrated systems, is clearly described by Gegner (2004).

The largest operations are driven by capital investments, often from meat-processing and marketing firms that are highly vertically integrated (MacDonald and McBride, 2009). The production facilities use full animal confinement, so that animals do not have access to the outdoors or to farm fields. Few of the large operations raise feed crops; most, if not all, purchase their feed inputs. Many of those operations typically specialize in a single stage of production such as animal finishing. Manure handling and facility cleaning is almost exclusively handled by liquid systems, with contracts to landowners who use the manure to produce a wide range of crops (MacDonald et al., 2009). Public controversy over many facets of animal raising and confinement has been escalating. Issues of concerns include animal welfare, widespread use of antibiotics for animal health, farm worker safety, safety of meat products, and environmental impacts on soil and water. These impacts range from nutrient and antibiotic loading on the land and in the waters surrounding the operations, and reduced air quality from volatile organics and other emissions from the large facilities. The debate is especially intense over the large-scale CAFOs for hogs, often referred to as “factory farms” given the scale of operations, their location, and the numbers of public issues surrounding them (Gurian-Sherman, 2008; Pew Commission on Industrial Farm Animal Production, 2008). This report does not assess the sustainability of CAFOs, but outlines in a section below the research needed for holistic evaluation and comparison of system types for each of the major areas of concern (system drivers).

Many small animal-producing farms (from a few hundred up to 3,000 acres) are typically structured for crop-livestock integration, producing feed crops and crop residues for bedding, and they often have at least a portion of the production cycle on rotated fields for farrowing or pasture. They typically use a dry manure-handling system and are almost exclusively owner operated. That type of farm ownership and structure is often a product

of traditional farm ownership and operation coming from a crop base, a pasture-based livestock operation, or a mixed crop–livestock operation where farmers are intensifying their operation and often purchasing additional feed. They are responding to a range of economic factors, including opportunities for local and direct marketing, branding, and specialty products for niche markets. A field-crop–hog integrated system, often referred to as “extensive” agriculture, is defined as farming in which large areas of land are used with low to modest outlays in capital expenditure (Honeyman, 2005). Outdoor swine production is a system that allows the pigs outside access including contact with the soil and growing plants (Honeyman et al., 2001b). Most low-confinement alternative systems share many commonalities.

Low-confinement hog systems have followed a trajectory of development that differs from the more common CAFO operations. They resemble the more traditional systems of field farrowing from which they have evolved more closely than they do a CAFO. Most low-confinement hog systems are medium- to small-sized farms and have hundreds rather than tens of thousands of animals (Honeyman, 2005). Farmer groups, cooperatives, and individual farmers use a wide range of reduced-confinement swine systems, with adaptations to many farm environments and types. A subset of low-confinement, extensively raised hog farmers follow guidelines established for U.S. organic systems by the National Organic Standards Board (NOSB). International organic guidelines are similar (Padel et al., 2004). Other farmers use some variation of those practices to raise animals “sustainably,” but most often they use chemicals for control of internal parasites or use alternative forms of nose rings for management of animal rooting and pasture or ground cover disruption. Three of the case-study farms in Chapter 7—the Rossman, Mormon Trail, and Thompson farms—raise hogs using bedding systems. Each of those farms raises feeder cattle on pasture, but none has extensive pasture for hogs. Scientific and technical resources available in the United States for alternative, low-confinement, extensive systems are summarized by SARE (2003) and Gegner (2004).

The primary guiding philosophy of all swine producers (CAFO and low-confinement) leads to an ultimate goal of maintaining animal health through management and provision of appropriate nutrition to optimize rates of growth and produce meat and carcass quality targeted to their specific markets, while having minimal adverse impact on the environment. In the discussion that follows, the committee applies the more stringent guidelines and literature from the “sustainable” and organic sectors as an example of production alternatives. There is extensive literature on the vastly differing strategies for both high-confinement and low-confinement systems.

NOSB sets the minimum requirement for organic systems in the United States. Many hog trade brands based on “humane” and “sustainable” criteria have most of the same guidelines, but they might differ in their latitude for control of internal parasites, tail docking, or use of nose rings. The guidelines highly influence the feeding, care, and handling of pigs and have a major influence on how pigs are housed, have access to grazing areas, and are allowed to socialize, which, in turn, highly influences the structure of farming systems. The most complex set of guidelines is outlined in the writings of Temple Grandin (2007, 2010) as “core standards.” Farmers who use those principles are guided by a philosophy that animals (regardless of species) be treated with respect and allowed to fulfill their instinctive natural behaviors without damaging their environment. Specific factors include:

• Animals must be given opportunity to care for, interact with, and nurture their young.

• They must be able to build nests during farrowing.

• They must have sufficient space to exercise and socialize with herd mates.

• A dry area where all animals can lay down at the same time without soiling their bellies must always be available.

• Air quality must be maintained for good health, including ammonia levels not to exceed 25 parts per million (ppm), with 10 ppm as the goal.

• Pasture or bedding are the preferred environments.

• Nontherapeutic use of antibiotics is prohibited. Animals that have been administered antibiotics must be segregated and not sold under the organic or (most) sustainable brands.

Following “instinctive natural behaviors” requires that animals have access to the outdoors and to pastures for much of the year. Pasture care requires plant cover, with active rooting of the plants to cover a minimum portion of the area, normally at least 70 percent. That requirement, by itself, requires animal-crop integration and a land base sufficient to support the swine herd. It also requires housing to be decentralized to provide shelter either within or in proximity to the pastures. Many farmers use existing farm buildings converted from former dairy or more intensive systems. Hoop houses are recommended for most new construction (Honeyman et al., 2001a). The outdoor and hoop structure research of the Allee Demonstration Farm in Newell, Iowa, is a key source of technology for many swine growers, regardless of region. Specific guidelines for such housing and management practices are available from many state extension agencies and from the National Sustainable Agriculture Information Service (National Sustainable Agriculture Information Service [ATTRA] of the National Center for Appropriate Technology [NCAT], 2009). The Sustainable Agriculture Research and Education program has many materials available (SARE, 2000).

Organic and “natural” pork farms in the Corn Belt fit well into the summary of such systems by Honeyman (2005, p. 15): “Most natural pork markets require outdoor bedding settings, no subtherapeutic antibiotics of growth promoters, no animal by-products in feed, and family farm production settings.” Animal housing is a critical factor for all farms. Organic requirements for space, bedding, and access to free space and to pasture are specific and auditable for each stage of animal growth according to USDA organic guidelines.

In addition, “Hoop-fed pigs have fewer aberrant behaviors and handle easier than confinement pigs. Health is similar except for an increase in internal parasites in hoop-fed pigs. Pigs in hoops are in larger groups than in confinement. Biosecurity in hoops is more difficult due to incoming bedding and open access” (Honeyman, 2005, p. 15). Organic farmers have a policy for rescue using antibiotics on occasional animals with a sickness problem, and then culling that animal from the certified market channel. Parasites are controlled with both careful sanitation and use of parasite-control chemicals. Because of parasite control (Baumgartner et al., 2003) and the problems of accessing certified-organic feed, few, if any, “natural” swine farmers raise organic hogs. Requirements for either bedded structures or pasture (or a combination) during grow-out place additional requirements on broad systems integration. The production of small grains for both feed and for bedding material, rotation of pasture to maintain mandatory levels of ground cover, and field conditions for the recycling of bedding and manure make overall farm integration an economic and environmental necessity.

Farrowing operations for organic and “natural” systems differ markedly from those of conventional systems. Sow health is maintained through diet and access to pasture for

exercise. Deep bedding systems are used for farrowing huts or pens, often referred to as the Swedish deep-bedding system. When sows are seasonally field farrowed, a limit of 10 or fewer sows per acre, depending on soil type, is used to maintain 80 percent or more pasture rooting and cover. Therefore, farm infrastructure varies, depending on farm history, climate, soil type, land slope, and hydrological characteristics. Some of that variability is documented in an Iowa State University study of four collaborating farms in southern Minnesota over two winters in 2003–2004 (Serfling et al., 2006). The greatest departure from industry practice in hog raising is in the farrowing requirements of most organic and other niche marketing swine operations. The prohibition of farrowing crates and the requirement for deep bedding and nesting capabilities for the sows influence many other system characteristics. Temperature regulations for sows and piglets are critical in winter, particularly in northern climates. The four farms studied used a wide range of farrowing and feeding structures. Results showed that the study farms had 11.0 pigs born live per litter and 8.8 pigs weaned per litter. Those numbers are comparable to Minnesota averages of 10.1 born and 8.7 weaned, and to national, industry-wide averages of 10.0 born and 8.6 weaned.

Herd genetics is extremely important to all niche-marketing swine operations. Most specialty farmers use crossbreeds of Berkshire, Chester White, and Duroc in their herds to achieve high meat quality, effective farrowing, and high growth rates. The herds’ performance is related to meat quality, animal behavior, and economics. Most cooperative sustainable animal operations recommend particular producers of semen and specific lines within those sources for farms using artificial insemination. Most niche-market brands have a certification and audit program for their contracting farmers.

Thompson Farm in Boone, Iowa, described in Chapter 7, is an example of a diversified pig-raising farm and has been a model for diversification and low-confinement swine production for many years. The 300-acre farm includes corn, soybean, oats, and hay, with 75 head of beef cattle and 75 hogs in a farrow-finish operation. The farm supports two families without outside hired help. The Thompsons learn and teach low-confinement principles and practices to many thousands of visitors to their farm.

Nutrient cycling, odor control, and greenhouse-gas emissions are inseparably linked in pig raising, and determined by the way in which the many kinds of structures are managed for manure collection and removal. All farmers with organic or sustainable certification use various forms of dry bedding for most animal shelter areas (Honeyman, 1996). Farrowing guidelines require dry bedding, while grow-out shelters, whether converted traditional barns or hoop structures, are often set up with the Swedish dry-bedding system. Those areas are kept dry with bedding and ventilation. Manure and urine is thus incorporated in high-carbon, dry crop, or sometimes woody residues. The animal wastes are collected and handled for eventual field application as dry material with reasonably high carbon-to-nitrogen ratio, thereby reducing both ammonia and volatile organic loss. A key factor is the type, amount, and frequency of application in the structures, with availability and cost of bedding material often the limiting factors. There is an extensive literature on bedding systems for farrowing, with the most comprehensive and often referenced done by Honeyman (2005). Research on the direct effects of the confinement portion of those systems is sparse. There is no effluent, either through soil below the structures or to surrounding areas from

bedded systems, from confinements operated in a dry condition. Field application of the dry-bedding pack has similar environmental impacts to spreading of other forms of high-carbon manure (discussed in Chapter 3). The bedding and manure mix is removed from the structures regularly for gestating sows and at time of marketing for grow-out structures. It could be stored in a holding area pending the appropriate time for field application to crop rotation fields within the mixed farming systems from which at least a portion of the grain and bedding are produced. Farmers typically manage nutrients on their mixed farms according to overall farm nutrient balance as determined by soil tests. (See the Bragger Farm in Chapter 7.)

Air quality in the confined areas is managed by ventilation and by bedding management. Several of the contract brand-name operations mandate that indoor air be maintained at under 10 parts per million (ppm) of ammonia. Limited research has been done on deep-bedded hoop structures. Air quality research on six different hoop structures for finishing swine sampled in Iowa, Illinois, and Minnesota containing from 600 to 2,520 head ranged from 2–10 ppm at the edge of the facility and from 0–2.5 ppm 100 feet downwind, with no detectable ammonia at 500 feet. Hydrogen sulfide ranged from 30 to 200 parts per billion (ppb) at the building edges and 5–7 ppb at 500 feet. All those levels were within sustainable guidelines for the structures themselves, and well below nuisance levels at 500 feet (Harmon et al., 2002). Emissions from the deep bedding will increase over time as the pigs age if sufficient fresh bedding is not regularly added to wet spots. There is a paucity of research data on gaseous emissions from operating systems. High-quality quantification is extremely difficult because of the high variability in environments over time and in the facilities themselves. A broad database for systems’ comparisons will require the ongoing development of process-based models adequately calibrated for broad assessment (NRC, 2003).

All of the “extensive” bedded systems described in the literature are operated on a land base and include crop rotations for feed and bedding. Many have feeder cattle, in addition, to maintain pasture. A few pig operations have a portion of their farrowing in the field in summer. The certification criteria for organic and the privately imposed guidelines for most commercial brands that are marketed as “sustainable”(see examples below) require a minimum of crop and root soil cover of 70 to 80 percent and have guidelines of a maximum of 10–12 sows/acre. Labor costs for field farrowing are the primary factor limiting the practice. Pasture-based finishing also has requirements for ground cover. All of the sustainable extension literature (SARE, 2000; Gegner, 2004) and most of the state-supplied literature for pastured hogs deals with recommended crop species for hog pastures. Several brand-certified and inspected market chains have guidelines for effectiveness of pasture ground cover management. No current research data characterize soil quality and erosion specific to extensive hog operations. The impacts likely would be similar to those for mixed crop–livestock operations. Landscape-level models of erosion and quality have been done in many areas for crop type, cover, rotation, and management practices and those models could well be applied to extensive hog systems. There are little research data on pasturing of monogastric species such as hogs or chickens, where a small portion of the diet is derived from the pasture itself instead of intensive supplemental feeding. Diversity in the landscape is similar to that of mixed crop–livestock systems, particularly when feeder cattle are included.

Research on alternative hog operations has recently been started or is underway in several states and institutions (see Gegner, 2004, for an extensive list). Comparative economic performance data are highly variable both because of the high variability in type of alternative operations and because of variability of boundaries placed on the system for analysis. The alternative systems have generally low capital costs, versatility of locations and environments, access to niche markets, integration with complementarities and synergies in a range of farm types, and the perception of positive animal welfare attributes. In comparing operations for extensive alternative systems, the macro data from the USDA Economic Research Service (Key and Roberts, 2007) and an extensive study on meat marketing practices (Lawrence et al., 2007) provide little insight. Even though they break out farms that market fewer than 1,000 hogs per year, they do not differentiate for confinement versus extensive or by the extent to which crop enterprises are truly integrated as affecting profitability.

Lower overhead costs have become a factor in the longevity of many small operations. Data from the statewide Iowa Swine Enterprise Records program from 1989 to 1993 show that outdoor farrow-finish operations weaned fewer pigs per litter and fewer pigs per sow per year, and they had lower overall herd efficiency than indoor confinement producers. Their fixed costs were $3.33 less per pig weaned for outdoor herds than for indoor. Total cost to bring a pig to market was $1.95 per hundred-weight (cwt), or $4.88 per 250-pound pig less for outdoor herds (Iowa State University Extension Service, 1996). Hoop structures have been in common use since the late 1990s. Their use lowers the per-animal overhead costs considerably and enables a higher management standard, particularly for those using deep-bedding systems.

Rate of gain and feed conversion efficiencies have been found to be seasonally lower for outdoor and hoop structures than for indoor confinement in bedded systems in comparative trials in the Midwest and in Canada. Multiyear, replicated seasonal trials at the Iowa State University Rhodes hoop research facility showed hoop structures, in summer, produce 4 percent greater average daily gain and required four fewer days to reach marketable weight as compared to the confinement system (Honeyman and Harmon, 2003). Feed intake, gain-to-feed ratios, and lean gain per day were the same for both systems. In winter, hoops had similar average daily gain, required more days to reach market weight (176 versus 172), and had greater average daily feed intake (2.54 versus 2.35 kg/d), less gain-to-feed efficiency (0.313 versus 0.341), less lean gain per day (312 g versus 322 g), and less efficiency of lean gain (0.130 versus 0.144). In winter, hoop-fed hogs, thus, had greater fat content. The seasonal drop in efficiency is typical for winter systems in the United States and Canada where temperature variation is high.

Using those data and a wide range of other Midwestern research and survey data, a series of production budgets have been constructed for niche-market pig production in Iowa and in similar environments (Lammers et al., 2007). Using conservative estimates of production for well-managed, small farm enterprises (2 litters per year, 7 weaned pigs per litter, and 2.5 production cycles per year in hoop structures, and a gain-to-feed ratio of 1:3.5), breakeven costs (including labor and fixed costs) are $48.28 per CWT for 270-pound pigs in farrow-finish operations. The breakeven costs were calculated assuming a price of corn at $3.65/bushel, full costs for oat straw and cornstalks for bedding, and no return for value of manure or bedding. Comparisons between a hoop facility using the Lammers data above and CAFO data for feeder pig production show a cost of $37.17/CWT for hoop-raised feed-

ers and $36.91/CWT for CAFO-raised feeders (Pew Commission on Industrial Farm Animal Production, 2008). Hoop systems operators benefit from lower fixed costs but higher operating costs from labor and some reduction in efficiency as compared to CAFOs.

Farmers who purchase feed benefited from the federal subsidy program from the period of 1997–2005 at an average rate of $0.54 per bushels of corn and $0.76 per bushels of soybean, which amounted to a subsidy of $3.28/CWT of live hogs. The subsidy is realized disproportionately to large producers who purchase most of their feed. Smaller producers raise a higher proportion of their own feed. In 1998, corn and soybean prices were sufficiently high to eliminate subsidy costs. The advantages of efficiencies in integration make extensive hog operations more profitable than specialized operations when crop subsidy payments are not considered (Flora et al., 2004).

In summary, modern, high-management alternative systems that are integrated into land-based crop systems can be equally economically productive and profitable on a perunit animal output basis. Feed requirements and labor costs are higher in high management alternative systems than in CAFOs, but capital investment is considerably lower.

Much, if not most certified, alternatively produced pork (under extensive systems, without antibiotics, with certified animal housing and handling practices) is marketed through niche-market channels. Niche-market chains generally characterize their products as having “superior or unique product quality and social or credence attributes” (Honeyman et al., 2006). While they purchase primarily from independent, individual farm owners (classified as “independent” in the USDA Census of Agriculture), these growers usually have marketing agreements with the marketing groups or chains, and are certified as raising pigs according to agreed-upon standards. In the 2007 Census of Agriculture (USDA-NASS, 2009), 87 percent of growers marketing 1000 animals per year declared themselves to be “independent.”

Surveys of 10 hog marketing groups in Kansas and Iowa showed the importance of strong leadership, hiring of a strong coordinator, good record keeping, provision of technical services, particularly on herd genetics, and marketing by carcass weight and quality (Tynon et al., 1994). Those characteristics are strongly seen in all today’s operations described below.

In Iowa, there were 35 to 40 active pork niche-marketing operations (Honeyman, 2005) in 2003. A study of two of the larger operations provides many details of their operations, including grower incentives, quality assurance, certification audits, and profit sharing (Hueth et al., 2005). The larger of the two was, at that time, engaging some 400 farmers and spread across 10 states. Most of its growers marketed fewer than 1,000 head per year. Price paid to growers was based on the commodity market, so it followed the annual and seasonal pattern of that national market. Prices in 2003 averaged generally $5.00/CWT (about 13 percent) above average prices received by growers in Iowa, and nearly $8.00/CWT (about 20 percent) above average prices paid by Excel, Tyson, and Sioux-Preme. The company paid a premium based on farmer evaluation by certification standards of up to $0.75/CWT. For the niche-market brands, farmers were penalized for low, rather than high, fat content, opposite to standards for much of the industry.

Variability in niche-marketing structures is extreme, with no single type seeming to have preference. Most have a high level of farmer input into structural decisions and farmer evaluation and reward–penalty criteria. Examples of some of those market chains (or brands) include:

• Eden Farms LLC (www.betterpork.com). Headquartered in State Center, Iowa, Eden Farms is a coalition of 28 farm families in Iowa, Wisconsin, Illinois, and Missouri. The farms raise Berkshire hogs, known for their high-quality meat, and the products are marketed through 10 distributors spread across the country. Farm sizes vary, ranging from farms of 300 sows down to as few as 10. Volume for 2008 averaged 218 hogs marketed per week.

• Organic Prairie Family of Farms (www.organicvalley.coop.). Headquartered in LaFarge, Wisconsin, Organic Prairie Family of Farms is a cooperative of 150 family farms that raise certified-organic beef, pork, chicken, and turkey. A small portion of those farms raise hogs under certified, annually inspected organic management (www.organicprairie.coop/faqs/organic-pork/). Their animals are never confined, never treated with antibiotics or synthetic hormones, and fed organic feeds.

• Coleman Natural Foods (www.colemannatural.com). Headquartered in Golden, Colorado, Coleman Natural Foods markets under several brands. Their pork sells under the name of Coleman Natural Hampshire^®. Their hogs are “raised with no antibiotics, no added hormones, 100 percent vegetarian-fed, humanely-raised and sustainably farmed.” They are not organic.

• Niman Ranch Pork Co. Headquartered in Thornton, Iowa, Niman Ranch Pork Co. is a subsidiary of Niman Ranch, Inc. (www.nimanranch.com/pork.aspx). The company has some 600 privately owned and privately managed family farms, clustered into seven (management) regions in 12 Upper Midwest states from Iowa to Michigan. As of 2009, it markets about 3,000 hogs per week, all raised under farmer-agreed-upon standards of animal welfare and management to assure a high-quality meat product.

Extensive pig operations are nearly all owner-operated. Many specialty niche brands require the farm operator to own the animals for their entire life cycle. Some larger units have two generations or siblings within the same family (as with Thompson Farm, described in Chapter 7), and others hire permanent workers from within the community. The guidelines and requirements for most pork niche markets require a high level of animal husbandry skills, so long-term worker commitment and training is important. The work in those operations is more diversified than in CAFOs because of the combination of housing and field operations. Temperature control in hoop buildings is moderated in winter by the bedding pack, but varies widely. Most guidelines set 10 ppm of ammonia as a target for upper levels, not to be exceeded for all but short spikes. Bedding and moisture management to achieve those levels also limit hydrogen sulfide (H₂S) to reasonable human comfort levels. The strategy for dry-bedding systems is to avoid creating odors and maintaining reasonable air conditions in the first place, instead of mediating odor and air emissions by engineering solutions.

Most niche markets are identified both by meat quality and the environmental and social considerations imputed in the product as part of brand marketing. Many brands hire outside laboratories to monitor samples from carcasses entering their distribution networks, with taste, fat content, and chemical characteristics used in marketing. In the Niman Pork Company farmer cooperator network, for instance, the handling of animals both on-farm and during shipping is audited and carefully managed both to keep consistent

with humane standards to minimize bruising and to reduce stress-induced meat quality changes. The meat from every farm is tested at intervals by a pork quality testing service of Iowa State University for moisture, acidity, marbling, color, and other characteristics to assure brand quality. Lactic acid content is measured as an indicator of stress during transport and handling. Farmers use the ratings to rank themselves in providing quality product, with annual incentives calculated on the basis of their scores. In general, alterative producers and many niche market brands produce meat with higher fat content, a darker red color, and a more distinctive taste, determined both by genetics of the herds for meat type and by access to outdoor and open spaces, which influence meat texture.

As mentioned in the guidelines, many niche-market brands do not allow antibiotic use in any of their marketed animals. Except for certified organic products, others use standard parasite control chemicals. The prevalence of methicillin-resistant staphylococcus (MRSA)¹ increasingly reported for confinement operations in Iowa and in several other U.S. locations and several developed countries (Smith et al., 2009) is not considered to be an issue for most alternative systems. No extensive MRSA surveys have been done for those operations, but as of yet, none of the niche market or organic pigs, or workers who volunteered to be tested by Iowa State University, has tested positive.

An increasing number of scientists are testing attitudes among rural residents and communities toward intensive animal agriculture (NRC, 2003). Studies indicate that rural residents and activists, while understanding the economic constraints that swine producers are under, strongly feel that large-scale confinement operations are, at least temporarily, eroding farmers’ traditional base of support (Pew Commission on Industrial Farm Animal Production, 2008). Residents tend to be more tolerant of swine facilities when farmers are long-time residents and are active in the community than of new, large-scale industrial facilities coming in under corporate ownership and management (Reisner and Taheripour, 2007).

Extensive, alternative hog production systems can be equally if not more productive than large-scale specialized operations, even if the significantly higher externalities of the large operations relying on liquid manure handling are disregarded. Small, integrated operations fit better into acceptable patterns of landscape use in and around rural communities. Many such operations exist in many parts of the United States, and they can provide ample examples and data points for comparisons with large-scale systems. Comparative studies of systems types using a holistic approach, looking at economic, environmental, and social factors embedded in a sustainability matrix for efficiency, resistance, and resilience across landscapes, are needed to identify how each system performs with respect to each of the four sustainability goals and to explore how synergies are achieved in each systems type.

Perennial crops generally have advantages over annuals in maintaining important ecosystem functions, particularly on marginal landscapes or where available resources are limited. Perennial grain agriculture, sometimes called natural systems agriculture, is an ecology-based approach to agricultural production in which perennial grain-producing

crops are grown alone or in mixtures. Growing perennial grains for food or perennial grasses for biofuel can potentially increase carbon sequestration in soil and mitigate nutrient runoff from agricultural fields. Perennial grain and perennial grass-based biofuel systems are being developed, and the following sections discuss their potential contributions to various sustainability goals.

Today most of humanity’s food comes directly or indirectly (as animal feed) from cereal grains, legumes, and oilseed crops, all of which are annual crops. Replacing some of the single-season crops with perennials would create large root systems capable of preserving the soil and would allow cultivation in areas currently considered marginal (Figure 5-1) (Cox et al., 2006; Glover et al., 2007). Perennial plants reduce erosion risks, sequester more carbon, and require less fuel, fertilizer, and pesticides to grow than their annual counterparts (Glover et al., 2007). Plant breeders see several opportunities for perennial plants to maintain their perennial characteristic and produce high seed yield for the following reasons:

• Perennials have greater access to resources over a longer growing season.

• Perennials have greater ability to maintain the health and fertility of a landscape over longer periods of time.

FIGURE 5-1 Root and top growth of annual wheat (at left in panels above) and its perennial relative, wheatgrass (at right in panels above), at four different times of year.

NOTES: Perennial crops have deeper root systems than annuals, providing access to more water and nutrients. Perennials also have a longer growing season, allowing more sunlight to be captured by the crop.

SOURCE: Glover (2010). Reprinted with permission from the American Association for the Advancement of Science.

• The unprecedented success of plant breeders in recent decades to select for negatively correlated characteristics in annual crops (such as seed yield and protein content) can be applied to perennial crop development. Recent advances in plant breeding, such as the use of marker-assisted breeding, genomic in situ hybridization, transgenic technologies, and embryo rescue, provide new opportunities for plant breeders to select for desired characteristics.

In the last seven years, plant breeders in the United States, Argentina, Australia, China, India, and Sweden have initiated plant genetic research and breeding programs to develop wheat, rice, corn, sorghum, sunflower, intermediate wheatgrass, and other species as perennial grain crops (Glover and Reganold, 2010). However, it could take 20 years to develop perennial wheat ready to be widely planted on farms. At present, it takes plant breeders more than a decade just to develop new varieties of annual wheat and ensure that they are ready to be widely grown for commercial use.

Comparisons of the effects of annual and perennial management systems on soil properties have shown that well-managed perennial systems compare more favorably than annual management systems. Robertson et al. (2000) found that perennial production systems of alfalfa, poplar trees, and perennial grass systems had higher levels of soil organic carbon and resulted in lower net greenhouse-gas emissions than annual cropping systems. Other researchers have similarly found positive effects of perennial vegetation on soil properties compared to annual cropping systems (Weil et al., 1993; Mummey et al., 1998; Karlen et al., 1999; Culman et al., 2010). Randall et al. (1997) also found perennial systems to be effective at reducing the potential for ground water contamination by nitrate leaching. Perennial grain agriculture is expected to provide similar benefits.

Depending on landscape management, the use of cellulosic feedstock for biofuel production can avoid some of the social and environmental concerns associated with corn grain ethanol and soybean biodiesel. As noted by Robertson et al. (2008b, p. 49), “Biofuel sustainability has environmental, economic, and social facets that all interconnect. Tradeoffs among them vary widely by types of fuels, and where they are grown and, thus, need to be explicitly considered by using a framework that allows the outcomes of alternative systems to be consistently evaluated and compared. A cellulosic biofuels industry could have many positive social and environmental attributes, but it could also suffer from many of the sustainability issues that hobble grain-based biofuels, if not implemented the right way.”

Unlike corn grain ethanol and soybean biodiesel, the feedstock for cellulosic biofuels does not have to be grown on fertile cropland. Some dedicated fuel crops (for example, switchgrass and native grasses) can be grown on marginal lands that are not used for food and feed production (NAS-NAE-NRC, 2009b). Other lignocellulosic feedstocks include residual products from farming (for example, corn stover) or forestry operations (for example, residues from forest thinning). However, if dedicated fuel crops displace food crops,

the social and environmental concerns pertaining to corn ethanol discussed in Box 2-2 would be relevant in the context of cellulosic biofuels.

Debate continues about the relative merits of crop mixtures, but agronomy and industry development have moved toward sole crops (for example, Miscanthus or switchgrass) suited to differing climates, soil types, and growing conditions. Perennial crops have many potential environmental benefits, including reduced soil erosion, greater efficiency of nutrient uptake, and greater attractiveness to wildlife. It is argued that the enhanced biodiversity of mixtures can add significantly to environmental benefits (Tilman et al., 2006), but the weight of evidence seems to indicate higher productivity and much greater ease of commercial production from monocultures.

Production research in the Corn Belt states includes model projections of potential of different land types (Nelson, R. for Kansas Biomass Committee, 2007) and a series of agronomic trials underway by USDA laboratories and by state universities. Research in Minnesota on the landscape positioning of perennial biomass crops using alfalfa, willow, poplar, cottonwood, false indigo, switchgrass, and a polyculture mix shows that different species can be used on lands with different characteristics (such as slopes, soil types, and water availability) to optimize biomass yields and improve environmental quality (Johnson et al., 2008). Existing precision geo-referenced yield monitoring of commercial grain crops can be a tool in that design. Benefits to such positioning not only include optimizing yield potential and field water availability, but also can greatly enhance nutrient recovery and cycling (Annex et al., 2007). Such energy crops, if properly placed in the landscape, have potential to increase productivity of land types, provide diversity of markets for farmers who produce food crops and animals, and could contribute to ecosystem services. They could serve as riparian buffers, filter strips, and nutrient traps and could stabilize fragile land on a gentle slope. They could, therefore, replace at least some of the noncommercial crops in set-aside and other programs that currently require government subsidy.

Lignocellulosic biofuels (including ethanol derived from biochemical conversion or gasoline and diesel derived from thermochemical conversion) have been estimated to have lifecycle greenhouse-gas emissions of close to zero (NAS-NAE-NRC, 2009b). If the lignocellulosic biomass is grown in an appropriate landscape, it can provide biofuel feedstock and enhance environmental quality and the quality of the resource base (NAS-NAE-NRC, 2009b). However, water use for converting biomass to liquid fuels could create competition for water with agricultural production. Biorefineries will likely be located close to where the biomass feedstock is produced. The amount of water required for processing biomass into ethanol is estimated to be 2–6 gallons per gallon of ethanol produced (Aden et al., 2002; Pate et al., 2007).

Dedicated fuel crops (for example, Miscanthus and switchgrass) can be grown on lands that might not be suitable for other crops and can provide an additional income source for farmers, but they are a single-market commodity. If they are to be used for ethanol production, their demand will depend on oil price, the percentage of ethanol that can be blended in fuel, and the number of flex-fuel vehicles, as discussed in Box 2-2. They can be used to produce gasoline and diesel by thermochemical conversion. Thermochemical conversion

technology is estimated to be ready for deployment by 2020, and the fuel products will be compatible with existing transportation-fuel infrastructure. In addition, dedicated fuel crops can be used for bioenergy production (NAS-NAE-NRC, 2009a).

In the preceding sections, four alternative system “types,” including organic, integrated crop–livestock, management-intensive rotational grazing, and low-confinement hogs were illustrated. Each type was selected because of its overall enterprise mix and structure, with components and practices that ostensibly lead to complementarities and synergies of resource use and containment, positive impacts on their ecological and social environments, and resistance and resilience in each of its resource domains. Each has substantial claims being made for its contribution to sustainability. Each has a large and growing number of farms in many parts of the country that are, or could, serve as research cases. Organic farms certified in accordance with USDA standards, for example, are found for most commodities, in every part of the country, and across a range of farm sizes. The case-study farms of Chapter 7 represent organic and other system types that have departed from the traditional conventional farms and moved much further along the trajectory toward improved sustainability. The four types presented above are described by research data that focus on component pieces of the systems, much of which is summarized in Chapters 3 and 4. The paucity of reliable data on holistic descriptions of those operations in the United States is evident. Holistic comparisons between system types aimed at improving sustainability are not possible with present data, given the multidimensional nature of sustainability as defined in Chapter 2.

What are the resource constraints for a systems design environment, and which systems and sustainable management practices best fit within the biophysical conditions and meet the social and economic sustainability goals? A few of the constraints coming from data of the above alternative systems include:

• Land capability classification, sensitivity to runoff, soil erosion, or other loss.

• Biodiversity needs (diversity of plants, wildlife, soil organisms).

• Water availability, alternative demands, projections for future needs and sharing.

• Sensitivity to water quality degradation and downstream hypoxia.

• Probability of extreme climatic events (flooding, short-term changes in water availability).

• Population density and exposure to odors, noise, or other “nuisance” factors.

• Support for the business community, employment needs, and social viability of local communities.

The most common “systems approaches,” and for the most part, the most useful, have been studies comparing integrative practices that are well-defined and are located within operating farm environments. Examples are tillage comparisons, cover crop integration into rotations, integrated pest management for particular crops such as tree fruit or certain field crops, and, in some instances, well-defined approaches such as organic and conventional approaches for a particular crop such as apples or cherries (Reganold et al., 2001; Peck et al., 2006). Such studies compare specific integrative practices within a whole-farm

context, where appropriate interactions can be defined and measured (Drinkwater, 2002; Snapp and Pound, 2008). The on-farm systems studies are usually conducted under experimental management by farmers and last for 5–10 years to measure intermediate-term effects. Those studies can be significantly cost-effective, but require considerable farmer (or farmer–community-of-interest) interest and support (Carter et al., 2004).

Research personnel manage a number of well-known, long-term systems studies in the United States on experiment stations. The studies are designed to measure crop performance and often soil and environmental impact over 15–20 years or longer. A few studies have century-old duration (Paul et al., 1997). The more modern ones (designed over the last 30 or so years) are replicated and sometimes have large plots size with ancillary smaller-plot experiments (Temple et al., 1994; Robertson et al., 2008a). They use planned rotations and integrative management practices and are designed to study comparative agronomic, horticultural, and ecosystem processes (see Box 3-3 in Chapter 3). Those carefully designed “experiments” are more appropriately “research platforms” within which specific “factor studies,” usually focused on specific biological process, can be conducted (Robertson et al., 2000; Hepperly et al., 2006; Cavigelli et al., 2008; Center for Integrated Agricultural Systems, 2009; University of California-Davis, 2009). Although those experiments measure specific farm enterprises (rotations and so on) within the context of local environments and ecologies, they are not whole-farm studies in that they do not represent true farm conditions of labor and equipment use, enterprise diversity, and a scale suitable to measure landscape-level impacts. Whole-farm studies are highly useful in quantifying biological processes and in calibrating models for use in widespread holistic systems comparisons. They are expensive to run, require stable and long-term institutional interest and funding, and have to be located within agricultural environments that represent large regional production zones for them to be both relevant and cost-effective.

A number of questions relating to environmental fragilities and constraints are important to consider. For example,

• Which systems of tillage and crop and animal diversity provide high nutrient flow rates (for high productivity) with farm- and landscape-level recycling and containment?

• What is the net nutrient flow into or out of production systems? For those with a large relative inflow (such as most large confinement operations), what is the “command” (distribution) area for nutrient dispersal for alternative scales of operations and what is the “life expectancy” of that land for phosphorus and other nutrient loading given alternatives for cropping or other use?

• Given the environmental conditions, which practices (for example, raising animals to optimize genetic immunity) or animal production systems would be least conducive to disease build up? What are the tradeoffs between those approaches and that of substitution of antibiotics?

• Could animal systems be designed to minimize the creation of odors and to optimize manure quality close to the source? If engineering solutions are to be depended upon to correct the problems after they occur, what are the tradeoffs?

• What are the economic, environmental, and social costs of the presence of antibiotic-resistant organisms within production facilities, in food products, or in the environment?

• What influence do subsidies to various sectors of agriculture have on the viability and productivity of alternative systems?

• What are the lifecycle energy costs for different systems types?

There are examples of whole-farm systems research in the United States (albeit with limited scope) that are highly productive and necessary, such as the examples cited above and in Chapter 3. “Whole-farm” studies, for the most part, have focused on economic performance or on efficiency of resource use such as energy, water, or output per unit of land. Those studies have been most useful where adequate numbers of farms have been selected to compare reasonably well-defined farming types. The organic versus “conventional” or nonorganic comparisons are a good example. Comparative studies work best where there are reasonably large numbers of comparable farms in a given geographical area (for instance, Lockeretz et al., 1984; Drinkwater et al., 1995).

Most “reasonable” models for sustainability of U.S. agriculture, if built on sound theoretical grounds, would include diversity in farm scale, structure, product output, and multi-functionality at each scale (Gibson et al., 2007). The objective of holistic comparisons, therefore, is not to identify the “best” system for each environment, but the relative strengths and tradeoffs for each alternative. It might well be that some conventional or alternative extremes of size or configuration are simply not worth trying to “fix.” As an example, agriculture as it now exists in water overdraft areas is clearly not sustainable.

In conducting the comparisons, farms that represent working examples of each comparison type would be selected scientifically. Data would originate from and process models would be base-calibrated for the selected farms. For example, with each of the four alternative types described above, hundreds of farms located in differing environments could be used for case studies. In meeting the environmental needs and constraints and answering the research questions above, one approach is to set specific targets for product output for a given geographical area or environment (whether number of animals, or of crop product output), then calculate the impact of a set of farms or facilities of each alternative on the many parameters to be considered.

The lesson learned from systems research is that it is complex. For systems research to be successful and cost-effective, the research objectives would have to be clearly defined and hypothesis driven. The design and expected duration of the research would have to be consistent with resources and objectives. The required data would be not otherwise available from other, less complex experiments that provide the needed data and interactions. The research would be done with the least complicated design that meets the requirements of the research. In developed countries as in the United States, a proportion of the more complex experiments and research platforms have not met expectations for output in comparison to the resources invested.

Many qualities of a sustainable agriculture are both defined and managed at aggregate levels beyond field and farm boundaries at the community, watershed, and river basin scales (as discussed in Chapter 2). That generalization is especially true for many social and economic effects at aggregate levels. (See Chapter 4.) Most of the foregoing discussion in this report on practices and farming systems has focused on comparative function and impact as measured by productivity, efficiency of resource use, environmental impact, and ecosystem integration as implemented within farms and the immediate environments of those farms. In the coming decades, the environments of those farms will change, as discussed in Chapter 2, and market requirements and opportunities will evolve. The land form and soil types within a farm that have been major determinants of farm crop and animal

selection and placement as guided by best management practices (USDA-NRCS, 2009) and evolving precision agriculture tools (Srinavasan, 2006) will be increasingly influenced by forces beyond the farm. Examples include regional water shortages, loading of major off-farm water bodies creating hypoxic zones, or new crop opportunities for energy production. The location and scale of animal enterprises will change, driven by such factors as regional phosphorus loading in the soil, water needs, or risk from flooding. Biological diversity and ecosystem health within landscapes are important factors across scales. Ecosystem health and “ecoagricultural” landscapes are of increasing sustainability concern and have a large and growing research literature (Scherr and McNeely, 2007; Van Bruggen, 2008). The diversity of crop, animal, and native vegetation areas within a landscape and the diversity of farm types that will provide them is thus important. The proportion of a landscape devoted to each farming system type, their positioning along gradients of land capability and to each other and to the practices employed all contribute to aggregate effects across larger scales. Those changes will be brought about by gradual changes within farms, as well as by multilevel policies to encourage structural changes across landscapes (Nassauer and Opdam, 2008).

Recent modeling application for two watersheds of the Upper Mississippi River basin illustrate the potential for shifting farming system enterprises, numbers, location, and balance to impact water quality (Burkart et al., 2005; Nassauer et al., 2007). Two watersheds in western Iowa counties having long-term river flow and water quality data, and a database of farming systems, crop acreage, and livestock census data, were modeled for sediment, nitrogen flow, water runoff, and other factors. Existing and three alternative crop, pasture, and animal component combinations were compared. Those studies then have formed the basis for subsequent landscape ecology studies, which made assumptions of altered percentages of the landscape occupied by the same types of farming systems found in the area (Nassauer and Opdam, 2008). Across many watersheds, the nitrate losses could be reduced by more than 40 percent by altering the percentages of the landscape occupied by the same farming system types. For specific watersheds such as Walnut Creek and Buck Creek, the losses could be reduced by up to 74 percent by changing the portion of the landscape devoted to cover crops and pasture, with actual increases in profitability. The most profitable alternative had a slight increase in the numbers of hogs, significant increase in cow-calf operations, more pasture and hay, and reduction in corn–soybean acreage. Societal costs and downstream impacts were estimated from fish kill and sediment-loading values. The potential benefits of introducing modern perennial energy crops into those systems are enormous. The availability of considerable stream flow and loading data and the availability of numerous models for different parameter flows are critical for that type of watershed analysis. Similar scenario studies have been conducted in Minnesota (Boody et al., 2005), which demonstrated that economic and environmental (water quality protection and conservation of biodiversity) benefits could be achieved through changes in agricultural land management without increasing public costs.

There are publicly available (digitized) sources of soil type, land classification, hydrology, climatology, and a host of demographic and other ecosystem parameters. Likewise, process-level models for most biogeophysical factors (such as nitrogen flows, carbon processes, and energy transformations and use) are under continual evaluation by scientists in the various agriculturally related societies and are in the public domain. Geographic information system (GIS) tools for agricultural use are evolving from precision agriculture research (Pierce and Clay, 2007), but modeling tools for use in the planning and assessment of agricultural landscapes are less well developed, and many are based on proprietary

software. There appears to be a large gap between the process-level work of agricultural systems and landscape architecture design and assessment.

There is a need for method convention, criteria, and definitions for developing alternative scenarios for generating landscape patterns and integrated assessments of alternative futures (Nassauer and Opdam, 2008). Such methods and tools would have a three-tiered function and application. An assessment at the national level for policy planning and macroassessment would be necessary. At regional and river-basin levels, such information and analyses are necessary for program planning and assessment. At the local and community level, action planning and processing tools would have to be available for local technicians and interface with databases and data from regional and national levels. Such tools will have a strong biophysical component, but also need the capacity for combining social and economic analyses in a holistic approach. It would seem appropriate for the USDA Economic Research Service, EPA, and possibly National Science Foundation to call for and support research and development of such tools. The tools would preferably be open access to encourage broad use by producer groups, civil society, and community organizations.

Such landscape planning would have major application and utility in linking farming system research and data with aggregation of farming system types and practices at larger scale to solve problems beyond the farm and community. Problems to be addressed include:

• Selection of best locations for introduction of energy-producing perennial crops and their processing plants to achieve productivity, landscape-level diversity, and desired multifunctionality. (See above section on perennial energy crops.)

• Location and numbers of animal systems and their scale of operations. (See above section on animal system alternatives.)

• Alternative farming system types and their diversity of practices in water-deficit areas.

Areas of ground water overdraft can be modeled, with aggregate deficits calculated on the basis of selection and distribution of farming system types having differing water demands. As an example, ground water overdraft in the High Plains has been studied in great detail, with regional and county-based mapping of drawdown and calculations made of estimated usable lifetime based on 1978 to 1988 trends. Records are mapped of actual withdrawal amounts. A study by the Kansas Geological Survey projects that significant regions of that state will have exhausted ground water supplies by 2025 (Buddemeier, 2000). Other states have ground water overdrafts for the Ogallala Aquifer of more than 50 percent of maximum sustainable yields. Clearly, water use for agriculture in those areas will have to decrease. Research by Texas Tech University in partnership with USDA shows that over a five-year period, integrated cotton and cattle systems reduced water use by 23 percent, nitrogen use by 40 percent, and increased profitability by about 90 percent (Allen and Brown, 2006). The integration of such systems across the landscape will require novel partnership arrangements for widespread implementation. Landscape-level modeling and planning for such efforts is highly quantitative and could be the basis for planning, policy formulation, and implementation. Concerns of water quality and availability can be addressed by:

• Selecting farming systems alternatives and their landscape locations for enhancing water quality and reducing hypoxia.

• Designing patterns of crop and animal diversity for enhanced ecosystem function.

The suggested “tiered” research approach with a strong implementation base for grassroots application will serve to link and enable communication among the many branches of science that are each addressing various pieces of the matrices described in this report. It would seem that modest interventions among key federal agencies could facilitate the tiered research that can enhance agricultural sustainability.

All farming practices and systems have interconnected impacts on a wide range of productivity, environmental, economic, and social indicators. The most widely used farming systems in the United States are focused on maximizing productivity and economic efficiencies, although there are a growing number of policy and economic incentives to minimize adverse environmental or social externalities.

Chapter 5 provides detailed examples of several innovative farming systems that are consciously organized to balance and optimize farm output, economic returns, environmental footprint, and social welfare. A review of scientific studies on various aspects of each of those systems—organic farming, management-intensive rotational grazing, and low-confinement hog production—suggests that they represent viable approaches to raising crops and livestock in a way that can improve the sustainability performance of U.S. agriculture along a number of important measures. Chapter 5 also discusses the development of perennial grain systems and perennial grasses for their potential to contribute to sustainable production of food and biofuel, respectively.

When viewed through the lens of integrated farming systems analysis, the success of each of those farming systems appears to build on opportunities for interaction and synergies among the major biological processes underlying agricultural production (soil, nutrient, water, air, pest, and disease management) discussed in Chapter 3. The most successful practitioners of those systems engage in a sophisticated management-intensive process of learning, experimentation, and adaptation of basic system principles to meet local conditions.

Although the evidence suggests that each of the four systems can make a contribution to improving the sustainability performance of U.S. agriculture, it is also apparent that gains along one sustainability dimension might require tradeoffs against progress on other dimensions. Examples include:

• Efforts to minimize nitrogen losses from farming activities to ground and surface water bodies might increase losses of nitrogen to the atmosphere, potentially increasing contributions to greenhouse-gas emission totals.

• Reduced levels of productivity (for example, output per acre) appear to be common in some types of U.S. organic farming systems, although reduced input costs and market premiums for organic products can lead to equivalent levels of economic returns to producers.

• Shifting from modern confinement livestock systems toward increased reliance on pastures or low-confinement housing can lead to reduced levels of productivity, introduce new challenges for animal disease management, and alter patterns of nutrient accumulation. Many of the tradeoffs are not well documented in published scientific literature.

To be most successful in accomplishing sustainability objectives, each of those four farming systems requires a high level of skill and adaptive management flexibility by the producer.

Although individual operations can improve the sustainability performance of their farming activities, the impact of farming systems on the environment, economy, and society also depends on whether there is a critical mass of such operations at the local, regional, or national scale. For example, until a significant fraction of U.S. farms or farmland is managed using organic farming practices, it is unlikely that the impact of organic farming on a wide range of national environmental, economic, and social indicators will be easily discerned. At the watershed scale, improvements in the environmental performance by some groups of farms may be overshadowed by adverse impacts associated with the activities of a few farms located in particularly sensitive areas. At the landscape scale, there is also evidence that a diversity of farms and farming systems can provide for greater biodiversity, ecosystem services, and aesthetic qualities. The specific arrangement of different types of farms on the landscape is an emerging area of study, and public policy tools designed to shape rural land use patterns are still in their infancy.

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