This literature review of integrating crops and livestock in an organic system was compiled by researchers from Rodale Institute, Iowa State University, and University of Minnesota for a 2014 grant proposal to the USDA National Institute of Food and Agriculture, Organic Research and Extension Initiative. That grant was funded under Grant No. 2014-51300-22541. Click here to read more about the research and results.
Organic Crops and Livestock
Driven by consumer demand, organic food sales have increased from $3.6 billion in 1997 to $31.5 billion in 2013 (OTA, 2014) and $52.5 billion in 2018 (OTA, 2019). Several factors have led to this increased consumption of organic foods in the U.S., including consumer preference for lower pesticide residues (Baker et al., 2002), nutrition and health concerns (The Hartman Group, 2006), negative environmental impacts associated with intensive conventional production (Venterea and Rolston, 2000), and the assurance of organic integrity through consistent federal organic standards (USDA-AMS, 2014). Farmers also are interested in producing organic crops that meet the “triple bottom line” of environmental sustainability, economic viability, and social equity. In recent years, organic farmers have become increasingly concerned about farm product/food safety, particularly important for farmers practicing integrated crop/livestock production (Pereira et al., 2013). Assuring food safety is critical in any farming operation, and, in the case of produce has been the subject of the recent federal law, “FDA Food Safety Modernization Act” (21 USC 2201; FDA, 2011), which will have far-reaching effects on the entire food supply chain.
The increased demand for organic products has outpaced adoption of organic production domestically with US farmers producing $7.28 billion of organic sales (USDA NASS, 2018), only 13.8% of the $52.5 billion-dollar organic industry. Currently, organic production in the U.S. is dominated by cash grain crops, with the majority of organic farmers in the Midwest and Pennsylvania using off-farm purchases to feed their organic animal herds. In the most recent survey, there were 366,881 organic corn and soybean acres among the 5.4 million organic acres in the U.S. (USDA-ERS, 2013). Production, environmental and economic benefits can be increased by enhancing the multi-functionality of the farm through integration of cash crops with forage crops for grazing and hay crops for livestock feed. In Iowa, organic grass-legume pastures are reported to supply up to 6,000 lb/acre dry matter per year (Acevedo et al., 2006). In Florida, cattle performance on bahiagrass pasture led to an average daily gain breakpoint between 1.4 and 2.0 kg forage dry mass per kg of animal live weight per day (Stewart et al., 2007). In Minnesota, organic dairy steers grazing predominately smooth bromegrass pastures had gains from 0.6 to 0.9 kg per day (Bjorklund et al., 2013). Additionally, incorporating a legume into grass-based pastures will increase overall forage quality and provide nitrogen to improve pasture health and stability. While it is known that hay production removes a significant amount of nutrients, including N and P from the soil, grazing aids in nutrient recycling through urine and manure excretion. Under moderate grazing pressures, soil P and K are mostly retained and remain in balance with crop needs, while soil N tends to be lost. The interactions between cropping and grazing systems on organic and conventional farms are not fully understood (Franzluebbers, 2007), particularly in organic systems, where the collection and distribution of manure is critical to the crop’s nutrient balance.
Historical Basis of Crop and Livestock Integration
The movement towards specialization of crop and animal production has separated integrated crop-livestock systems from their historical roots over the past century (Russelle et al., 2007). Cattle were an integral part of the farm landscape where they recycled nutrients from grass and grain produced on the farm (Flora, 2003) and farmers managed their land-based resources to maintain adequate soil fertility to sustain crop and animal production. By 1996, less than 10% of U.S. farms integrated crops and livestock (Krall and Schumann, 1996). However, contemporary models of profitable integration of crops and livestock, known as ley farming, are found in New Zealand and Australia, where rotating several years of grain crops with 2 to 5 years of grazed grass-legume pastures helps meet self-sufficiency goals (Haynes and Francis, 1990; Carr et al., 2005) and increases energy output (Nguyen and Haynes, 1995).
Soil quality improvement and nutrient cycling: Building or maintaining soil carbon and nitrogen pools for crop use is an important consideration in the evaluation of sustainable farming systems. Beneficial effects from integrating livestock into crop rotations have been associated with improvements in soil quality, including enhancement of soil organic matter, soil physical condition, and disease suppression (Jawson et al., 1993). Well-integrated crop-livestock systems mimic natural energy and nutrient cycles through ruminant conversion of cellulosic feedstuffs into protein and recycling of nutrients from livestock manure into crop cellular structure (Gates, 2003; Oltjen and Beckett, 1996). Incorporation of manure and crop residue inputs sequesters carbon in soils, improves soil function and mitigates erosion (Russelle and Franzluebbers, 2007). Franzluebbers (2005) found that carbon accumulation following grass pasture establishment averaged 1 Mg/ha/year. Katsvairo et al. (2006) also reported that a cattle-perennial grass rotation increased organic matter content and reduced nitrate leaching in peanut and cotton cropping systems. Management of available nutrients is necessary to support sustainable plant production particularly in organic systems, where fertility inputs are limited (Goulding et al., 2008). The complexity of nutrient cycling and availability in grazing systems is influenced by soil processes, plant species composition, stocking rates, supplemental feeding, and many other factors affecting inputs, exports and losses (Rotz et al., 2005). Greater retention and nutrient use efficiency within dairy production systems, for example, can have positive feedbacks for milk production and farm economy (Fanguerio et al., 2008; Ryan et al., 2011). In order to establish new, economic and environmentally beneficial grazing systems an understanding of nutrient cycling and efficiency in these production systems has to be established. Whole-farm models and nutrient balance sheet approaches, which require the assessment of nutrient pools, inputs, exports and losses, can be used to evaluate and establish best management systems for ruminant production (Dou et al., 1996; Rotz et al., 2007).
Crop Yield Enhancement
The literature suggests that with an integrated pasture/crop rotation, crop yields remain comparable or superior to continuous cultivation. Franzluebbers and Stuedemann (2004) reported no negative effect from grazing on subsequent grain crop biomass. Corn grain yield was found to average 3.6 Mg/ha following a 5-year-old pasture of either fescue or bermudagrass in Georgia and South Carolina (Parks et al., 1969). Adams et al. (1970) attained 11 to 24% greater corn yield following sod crops compared to continuous corn, while Franzluebbers and Stuedemann (2004) obtained wheat yields of 3.8 Mg/ha and sorghum yields of 5.1 Mg/ha following grazed crops of pearl millet and rye, respectively. Grain yield was greater in tall winter wheat varieties that were provided adequate fertility and moisture and grazed only to the joint stage compared to ungrazed wheat (Redmon et al., 1995). Hill et al. (2004) reported an addition of 0.1 Mg/ha of cotton and peanut yield in rotations that contained grazed rye or ryegrass preceding the crop. Grain crops interseeded into perennial forages are highly dependent on adequate moisture and minimal competition between forage and crops (Franzluebbers, 2007). This project will use sequential plantings of grain crops and forage/pasture in order to obtain consistent yields.
Grazing providing ecosystem services: Soil compaction from livestock movement is cited as a potential problem in integrated crop-livestock rotations, but Studdert at el. (1997) found that all soil quality indicators, including reduced bulk density, signifying low compaction, increased with perennial pasture in long-term rotations. Krenzer et al. (1989) found that soil strength increased with cattle grazing of winter wheat. Diaz-Zorita et al. (2002) and Garcia-Prehac et al. (2004) reported the greatest reduction in soil compaction resulted when conservation tillage was included in these rotations. Franzluebbers and Stuedemann (2004) found that soil penetration resistance was higher under grazed than ungrazed forage crops, depending upon soil water content, but that increased amounts of soil carbon from manure incorporation and cover crop additions may mitigate soil compaction issues (Franzluebbers and Stuedemann, 2005). In systems where nitrogen fertilizer was applied, more than 64% of applied nitrogen accumulated as soil organic N in grazed bermudagrass pastures compared to non-grazed pastures (Franzluebbers and Stuedemann, 2003b). Soil microbial biomass, another indicator of soil quality, also accumulated to a greater extent under grazed bermudagrass pastures (Franzluebbers and Stuedemann, 2003a). Thus, additional research is needed on the effect of grazed and non-grazed pasture crops within long-term crop rotations in organic systems where tillage is typically used for weed management (Delate and Cambardella, 2004).
Interruption of Pest Cycles
Crop insect pest and disease interruption from rotating grain crops with forage or cover crops has been reported (Snapp et al., 2005). Reductions in peanut stem rot (Brenneman et al., 2003) and nematodes in vegetables (Sumner et al., 1999) and soybean (Rodriquez-Kabana et al., 1988, 1989) were greater following bahiagrass pasture. Rye, lupin, sunnhemp, velvetbean and sorghum also have been shown to repel nematodes. Hartzog and Balkcom (2003) reported that bahiagrass and bermudagrass in a cotton or peanut system aided in reducing nematodes and other pests. Sod-based crop rotations have also been shown to interrupt animal parasitic cycles (Franzluebbers, 2007). Loomis and Conner (1992) reported a reduction in parasites when grazed forage crops were rotated with wheat crops. Finally, grazing cattle on pasture minimizes the risk of disease epidemics often seen in concentrated cattle feeding areas (Flora, 2003).
Weed Pressure Reduction
Many forage crop species have been reported to help break weed cycles in annual grain crops through competition, allelopathy, and microclimatic alterations (Gardner and Faulkner, 1991). While the interactions between weeds and grazing-cropping are not well understood, indications are that cattle grazing may control some invasive grasses; however, animals can also vector viable weed seeds to other areas through their excrement. Entz et al. (1995) reported weed pressure reductions when forages were integrated with wheat and other grain crops, with benefits continuing to accrue when grazing was included (Entz et al., 2002). Martin (1996) cited grass weed reductions when wheat was rotated with a grazed pasture crop.
Animal Performance and Health
Cattle raised on a plant-based diet in outdoor conditions provide economic and environmental benefits. Franzluebbers and Stuedemann (2004) found that cattle weight gain averaged 287 kg/ha and 419 kg/ha, respectively, on winter crops of rye and pearl millet. Steer performance on winter wheat grazed for 84 to 115 days was approximately 2 lb/animal/day at a stocking rate of 2 head/acre (Horn et al., 1995). Swath grazing also led to high feed efficiency for beef cows during a 54-day winter grazing period in North Dakota (Neville et al., 2007). The UI Livestock Integrated Focus Team transitioned the Schuette Farm of Breese, Illinois, to an integrated system and reduced their stored feed needs from 5,000 lb/cow/year to less than 1,000 lb, with no loss of productivity (Univ. of Illinois, 2008). Nutritional benefits of a plant-based diet for cattle include higher concentrations of omega-3 fatty acids, such as conjugated linoleic acid, which have anti-inflammatory and anti-coagulant properties (Daley and Abbott, 2006; Flora, 2003; French et al., 2000).
Food Safety Issues
Food safety practices to reduce toxins and microbial contamination are on the minds of all farmers, but particularly for farmers who integrate animals and crops in the same system. Studies comparing organic and conventionally raised livestock and pasture crops have found, in general, no significant food safety differences between conventional and organic systems (Bourn and Prescott, 2002; Maffei et al., 2013; Oliveira et al., 2012; Blanco-Penedo et al., 2012). In one study, it was found that conventional wheat had greater mycotoxins in a pilot project, but no significant differences were found in a more extensive experiment. In a livestock comparison in Spain, there were no food safety differences in organic or conventional beef cattle, but organic beef was reported to have higher quality. In a comparison survey of organic versus conventional broiler chickens, no significant differences were found in Salmonella presence, but Campylobacter was higher in the organically raised broilers. Grazing systems that reduce the larval or shed load of internal parasites will enhance cattle productivity on organic pastures (Larsen, 2006). Continuously grazed pastures fail to break the life cycle of these parasites, whereas rotational grazed pastures frequently reduce the parasite larval load (Stromberg and Averbeck, 1999). This project will explore a relatively new research area of integrating livestock within cropping systems and examining the effect on plant and animal health and product safety.
Stuedemann et al. (2003) estimated that the conversion of 10% of the Southern Coastal Plains to pasture would result in an annual gain of 40% more beef cattle and increased economic benefits, through a reduction in input costs and higher land productivity. Gardner and Faulkner (1991) found that whole farm income was increased by 20% with the addition of livestock in the farming system. Hill et al. (2004) reported an additional $311/ha in farm income from cattle grazing a winter cover crop of rye or ryegrass, while Gamble et al. (2005) obtained $185 to $200/ha each year cattle grazed winter cover crops. Carr et al. (2005) averaged a $65/acre return to labor and management in an integrated system compared to negative values for grain crops alone. Economic performance of the farm can be enhanced when producers feed their forage crop standing or windrowed, graze or bale the excess crop for winter-feeding, or store for later sale. Acevedo et al. (2006) found annual organic grass-legume pasture costs were $114/acre, with organic hay obtaining a 10-30% premium over conventional prices. Through more effective coordination among the various market participants, improvements in average beef quality have emerged (Hueth and Lawrence, 2002), either as members of an organic marketing cooperative, such as Organic Valley/Organic Prairie, selling individually, or by marketing directly to retail stores. Market benefits in an alternative system include active participation on the part of the producer in the entire value chain, as opposed to the conventional system where disjointed and mistrustful relationships exist between cow/calf operators and feedlot/packers (Flora, 2003). Incentives to produce organic beef include organic premium prices, often garnering 50% more than conventional prices, and the potential to export to countries, like the E.U., that have banned artificial hormones (Flora, 2003).
The Need for Additional Research on Integrated Systems
Currently, there is limited information on matching cropping and grazing cycles with climatic conditions for optimal crop and livestock production (Franzluebbers, 2007). Re-integrating livestock onto the farm landscape would have multiple benefits, including enhancement of soil quality and potential mitigation of pests. The protection or enhancement of carbon and other nutrients in soil organic matter is at the heart of the organic regulations, in order to maintain soil fertility and structure in sustainable systems (Manley et al., 2007). Organic producers surveyed in our region are striving for closed, integrated organic farms, relying on on-farm or locally produced inputs as much as possible to meet crop and livestock needs for food and nutrition. Building or maintaining soil C and N pools for subsequent crop use is an important consideration in developing sustainable farming systems. In national surveys of organic farmers (OFRF, 2007), weed management and soil fertility have been cited as prominent areas of concern. Researchers have confirmed that incorporation of manure and crop residues sequesters C in soils, improves soil function, and mitigates erosion (Russelle and Franzluebbers, 2007), and that long-term organic farming and manure application enhances nutrient cycling and pest suppression by promoting soil quality and biodiversity (Birkhofer et al., 2008; Carpenter-Boggs et al., 2000; Pimentel et al., 2005). Mechanisms underlying improved environmental conditions on organic farms include improved water and soil nutrient retention due to enhanced soil organic matter (SOM) content resulting from diverse crop sequences, and application of organic-based amendments such as cover crops and manure (Liebig and Doran, 1999). Integrated crop-livestock systems provide opportunities to optimize agroecosystem services, including recycling of nutrients from livestock manure for crop uptake and back to livestock as feed and forage. Removing carbon from the atmosphere and recycling it through plant-based systems may also prove to be a significant factor in mitigating the rate of global climate change. With cheap feedstocks declining, alternative sources of fertility, based on the ecological principles of biological nitrogen fixation from forage legumes and nutrient recycling, must be developed for organic, as well as, conventional farms (Badgley et al., 2007). Through increased use of strategies that enhance or sequester carbon in agricultural soils through manure and plant residues (Gaskell et al., 2000), the ‘carbon footprint’ of agriculture will be greatly reduced. Teasdale et al. (2007) found that soil improvements occurred when conventional, no-till farming practices were replaced with organic farming methods, even though tillage was used in the organic systems. Soil C and N were higher after nine years in an organic system compared with three conventional, no-till systems, two of which included cover crops.
While often cultivated for different attributes, forage crops, pasture crops, sod crops, hay crops and cover crops can be used in integrated crop-livestock systems. Cover crops demonstrating potential for livestock grazing for our region include wheat, rye, oat, barley, annual ryegrass, hairy vetch, common vetch, crimson clover, orchard grass, and tall fescue (Sojka et al., 1984), winter pea, subterranean clover, lespedeza (Duck and Tyler, 1991; Rao and Phillips, 1999; Rao et al., 2003; Reeves and Delaney, 2002). Hendrickson et al. (1963a) estimated that soil loss could be reduced from 45 Mg/ha under a cropping system (cotton) to less than 1 Mg/ha under perennial grass, but even without full scale conversion to pasture, integrating a 3-year rotation of oat/lespedeza forage–lespedeza–cotton led to a reduction in soil loss of 55 Mg/ha when compared to losses in continuous cotton (Carreker, 1946), and a reduction of 10 Mg/ha in an oat/vetch/sunnhemp forage–peanut rotation compared to continuous peanut (Hendrickson et al., 1963b). The effect of the forage crop in the rotation has been found to last for several years. As Giddens et al. (1971a, 1971b) demonstrated, soil organic nitrogen released following a tall fescue forage crop was utilized by a corn crop for up to 5 years. Integrated grazing operations could also lead to enhanced air and water quality through uniform distribution of manure across the landscape matrix in contrast to concentrated areas (Grierson et al., 1991). Forage and pasture crops reduce water and nutrient run-off and improve water infiltration (Gardner and Faulkner, 1991), and, as Hartzog and Balkcom (2003) found, water was conserved in the soil profile when bahiagrass and bermudagrass were integrated into cotton and peanut rotations.
Overgrazing is an issue that requires attention, particularly where vegetative cover, diversity, soil quality, ground- and surface water quality are negatively impacted (Flora, 2003). While it is known that hay production removes a significant amount of nutrients, including N and P from the soil, grazing can aid in nutrient recycling through urine and manure excretion. For example, under moderate grazing pressures, soil P and K are mostly retained and remain in balance with crop needs, while soil N tends to be lost. Additionally, grazing behavior of individual animals may influence the distribution of nutrients across the field, affecting subsequent grain production, whereas increasing the grazing rotation helps to alleviate animal congregation effects on soil nutrient distribution. Franzluebbers and Stuedemann (2004) reported a neutral effect of cattle on subsequent grain crop biomass and commensurate animal weight gain on forage crops integrated in a sorghum and wheat cropping system, with system productivity from combined crop and livestock components enhancing economic returns. Production, environmental and economic benefits can be achieved by increasing the multi-functionality of the farm through integration of forage crops with grain crops, but there is a paucity of information on integrating short-season forage crops in crop-livestock systems (Gardner and Faulkner, 1991), and virtually no information on these effects within organic systems. Developing effective parasite control in integrated systems is also not well understood and is included in this project.
Knowledge and skills that may be improved by integrating crops and livestock include herd management and health, fencing practices, water provisioning technology, balancing year-round forage supplies and labor, and securing potential additional land to account for grazing needs (Gardner and Faulkner, 1991). Multiple studies have associated changes in agricultural land use with competing uses (Moak et al., 1994), farm sector structural changes (Offutt, 1997), and changing farm-occupation opportunities (Hines and Rhoades, 1994). Because the majority of U.S. farms, including those with grass-based operations, consists of small and mid-sized operations that are more diversified, and emphasize family relationships, relying less on hired labor (Winrock International, 2001), it is critical to understand their value systems, and contrast how they negotiate profit compared to larger, less diversified operations (Johnson, 1994). This project is primarily focused on organic cow/calf operations on small- and medium-sized farms, since cow/calf producers normally rely on grazing (Flora, 2003). In a 2002 survey of producer attitudes and limitations of a grass-based system in Iowa, 84% of respondents stated that they would be willing to include forages because it is a “more environmentally sound use of the land,” and 32 percent indicated that they would be willing to change because it would lessen risk (Hanson et al., 2002).
In addition to economic values, the social values underpinning integrated, organic systems, such as maximizing investment in natural capital; reducing pollution and harmful health effects derived from persistent agrochemicals in conventional agriculture; enhanced animal welfare from a grass-based environment; and family-community interactions around changing landscapes and their implications will be assessed in this project. Of key importance is labor, as labor needs were found to increase by 50% when livestock were added to the farming system in North Dakota, with 15% of that increased time overlapping with crop management times (Gardner and Faulkner, 1991). Because education and experience are cited as the most promising methods for overcoming many social barriers to adoption of integrated crop-livestock systems (Franzluebbers, 2007), iterative processes will be established, where participants will share positive and negative aspects of integrated systems.
In contrast to current research and extension programs emphasizing larger output per farm (Flora and Francis, 2000), this project will inspire innovation, resilience and more alternatives for small- and medium-sized farming operations that enhance information flow between producers and end users of their products (Flora, 2001). Social barriers must be evaluated, however, in order for the integrated crop-livestock systems to progress. Lack of infrastructural support and insufficient information on balancing labor needs must be addressed to accelerate acceptance of these systems (Hardesty and Tiedman, 1996). Indicators of farm and household sustainability from integration of organic crop and livestock components will be assessed through surveys and focus groups. Indicators will include, but are not limited to, economic stability, soil and water quality, crop and livestock performance and health, energy use, working conditions, and social acceptance. The attempt to understand the dimensions and dynamics of producer decisions may contribute to the formulation of more effective agricultural policies in the interest of sustaining grass-based practices (Dixon, 2000). Successful examples of conversion and market demand, demonstrated through this project, will help producers determine if these niche markets are appropriate for them (Acevedo et al., 2006). Because research to build a more sustainable agriculture requires a systems perspective with high farmer participation (Flora, 1992), organic farmers are included in project design, execution and evaluation. Using the definition of sustainable agriculture put forward by Francis and Youngberg (1990), this project will reduce environmental degradation, maintain agricultural productivity, promote economic viability in the short- and long-term, and help to maintain stable rural communities and quality of life.