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Production Papers

Sod–Livestock Integration into the Peanut–Cotton Rotation

A Systems Farming Approach

^a Univ. of Florida, North Florida Research and Education Center, 155 Research Road, Quincy, FL 32351
^b Univ. Auburn, Wiregrass Research and Extension Center, 167 Highway 134 East, Headland, AL 36345

^* Corresponding author (katsvair{at}ufl.edu)

Received for publication March 23, 2005.

	ABSTRACT

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Contemporary thinking encourages diversified cropping systems as a way to sustain crop yields, protect the environment, and increase wildlife habitat. This paper reviews the benefits of diversifying the traditional peanut (Arachis hypogea L.) and cotton (Gossypium hirsutum L.) production system to include perennial grasses such as bahiagrass (Paspalum notatum Fluegge) and bermudagrass [Cynodon dactylon (L.) Pers.] and incorporating cattle (Bos taurus) into the system. Perennial grasses improve soil quality by reducing soil erosion and nitrate (NO₃) leaching, increasing organic matter (OM) content, water infiltration rates, and the abundance and diversity of micro and macro flora and fauna. Cotton and peanut grown after perennial grasses are deeper rooted, have more vigorous growth, can better withstand pest pressure and environmental stresses, and often have higher yields. Including livestock in the cropping system makes more efficient use of climate and farm resources by extending the period of productive plant growth, improving economic returns, and reducing risk by diversifying the products available for sale.

Abbreviations: CRP, Conservation Reserve Program • CT, conservation tillage • IPM, integrated pest management • OM, organic matter • SE, Southeast

	INTRODUCTION

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
CROP ROTATIONS have been in existence and advocated for several centuries. Farmers and researchers have always known that crop rotations increase crop productivity. However, farmers tend to specialize in the crops they grow due to environmental constraints, social norms, or economics and infrastructure. Consequently, the same crops are often grown in short rotations (1–2 yr) or without rotation. Limited 1- or 2-yr rotations become susceptible to classic problems akin to monocultures such as stagnant yields, soil degradation, and survival and adaptation of pests and disease to the rotations (Crookston, 1995; Zentner et al., 2001; Tanaka et al., 2002). Due to these problems, there is now a global movement toward diversifying cropping systems to include those that are more environmentally friendly and sustainable. This sometimes necessitates choosing farming practices not necessarily based on the highest yields and economic returns, but on socially and environmentally acceptable practices (Zentner et al., 2002) or for government regulations and/or incentives. Furthermore, as is the case with agronomic management challenges, socially and acceptable environmental norms are unique depending on geographical location, philosophical thinking at the time, and prevailing economic trends. While most successful business ventures are dynamic and able to respond to changing environmental and economic conditions, most farming systems are not as flexible and often depend on the infrastructure in their area. This makes farming one of the most challenging enterprises, requiring farmers to constantly make decisions with limited choices (Tanaka et al., 2002). Advances in technology, research, education, and extension have alleviated some difficulties associated with farming, but nonetheless, have not bridged the gap necessary for farm profitability, and (as a result), farming has not kept abreast with other business ventures. This is evident when one looks at the decrease in the number of commercial farms in the USA. Because most of the management difficulties experienced by growers are interlinked, there has been some interest in taking a systems approach and looking at a multitude of factors and their interactions in developing diverse farming systems. A well-chosen diversified farming program can alleviate some of the problems through efficient utilization of resources and introduce buffers against climatic and price fluctuations (Tanaka et al., 2002; Zentner et al., 2002). Such an approach is similar to a strategy of investment portfolio diversification as employed by financial managers.

A common row crop farming practice in the Southeast (SE) is to grow a two crop rotation of peanuts and cotton and occasionally a small grain winter cover crop for many years under conventional tillage. This traditional system leads to soil degradation and loss of OM (Reeves, 1997; Reddy et al., 2004). Moreover, the sandy soils of the Southeast Coastal Plain are inherently prone to erosion. The high potential for erosion further complicates soil management and results in losses in productivity and environmental pollution. The current system also results in pest and disease buildup and stagnant yields. A USDA (2004a) report showed that peanut and cotton yields in the SE have been stagnant for the past 15 yr although higher-than-normal cotton yields were observed in 2004 and 2005. On the other hand, most beneficial effects of rotations are realized with crop diversification (Elkins et al., 1977; Hagan et al., 2003; Wright et al., 2004; Katsvairo et al., 2004b). We hypothesize that using perennial grasses such as bahiagrass or bermudagrass in the traditional peanut–cotton rotation would lead to a rotation that increases yield, improves soil properties, and increases farm profit. Our objectives are to review and address the main production problems in peanut and cotton and evaluate how the use of sod-based rotations, integrated with livestock, could lead to a more sustainable production system with less risk and increased environmental stewardship for the SE. Because current philosophical thinking emphasizes environmental stewardship, our review highlights the potential environmental benefits of the system. Not all details of an integrated crop/sod/livestock cropping systems have been researched extensively, as a result, this review draws inferences in some cases. The review is divided into 2 sections. The first section focuses on diversifying the traditional peanut–cotton rotation to include bahiagrass. The second section discusses the benefits of introducing livestock into the bahiagrass/peanut/cotton cropping system.

	CONSERVATION TILLAGE

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Cotton
Diverse rotations can be effectively used in both conservation tillage and conventional tillage systems. However, more benefits are derived when diverse rotations are coupled with conservation tillage (CT) (Reeves, 1994, 1997) and integrated pest management (IPM), resulting in improved soil quality and possible synergistic effects. Doran and Parkin (1994) defined soil quality as the capacity of a soil to function within ecosystem boundaries to sustain biological productivity, maintain environmental quality, and promote plant and animal health. It is essential that CT be adopted in cotton grown in the SE because cotton is generally grown in sandy or silty soils that are particularly prone to sheet and rill erosion (Belvins et al., 1994; Boquet et al., 2004). The SE has the most successful story of adopting CT in the USA. According to the National Crop Residue Management Survey (2002), approximately 85% of all cotton under CT in 2002 in the USA was grown in the SE. This marked an increase of more than 750% in the acreage of cotton grown under CT over a 10-yr period (National Crop Residue Management Survey, 2002). During the same time period, the acreage planted to cotton in the SE increased by 769000 ha to 2.1 million ha (National Crop Residue Management Survey, 2002). Literature from the 1980s showed that in some southern states such as Alabama and Mississippi, cotton had been grown under conventional tillage for more than 100 yr (Bauer and Black, 1983). Conventional tillage operations destroy soil structure, reduces soil OM, negatively impacts beneficial soil micro and macro fauna and increases soil erosion through runoff (Paoletti et al., 1993; Jordan et al., 1997; Magdoff and van Es, 2000; Krupinsky et al., 2002). On the other hand, CT results in less disturbance to soil structure, increases protective crop surface residues after harvest and adds OM resulting in increased nutrient and water-holding capacity (Hendrix, 1999; Unger and McCalla, 1980; Johnson et al., 2001; Nyakatawa et al., 2001a). Several authors report increased cotton yield with CT compared to conventional tillage (Delaney et al., 1996; Boquet et al., 1997; Hunt et al., 1997). Cases of no yield difference or reduced yield between CT and conventional tillage are also documented (Daniel et al.,1999; Stevens et al.,1992; Pettigrew and Jones, 2001; Wheeler et al., 1997). When realized, the higher yield under CT has mostly been attributed to improved soil moisture retention and utilization (Daniel et al., 1999; Baumhardt et al., 1993). The reduction in yield under CT is attributed to difficulties in establishing uniform stands, and reduced growth and development due to soil compaction and the consequent reduction in water availability (Pettigrew and Jones, 2001; Schwab et al., 2002; Raper et al., 2000).

Peanut
Peanut growers often use clean tillage, which involves several tillage operations on the field. The goal is to completely bury pathogen inoculum which may be present on plant residues, and by doing so, reduce the incidence of soil borne diseases (Sholar et al., 1995; Cox and Scholar, 1995; Johnson et al., 2001). New resistant varieties and fungicides now provide effective control for most peanut soil-borne fungal diseases, enabling peanut growers to use CT techniques (Johnson et al., 2001). Literature, however, shows contrasting reports on how CT affects crop yield compared to conventional tillage practices. While reports exist of lower peanut yields under reduced tillage compared to conventional tillage (Jordan et al., 2001; Grichar, 1998; Brandenburg et al., 1998; Cox and Scholar, 1995), research showing no yield differences between conventional tillage and CT have also been reported (Dowler et al., 1999; Sholar et al., 1993). On the contrary, increased peanut yields under reduced tillage have also been observed (Hartzog et al., 1998; Baldwin and Hook, 1998; Williams et al., 1998). Marois and Wright (2003) not only reported higher peanut yield but also observed reduced disease incidence under CT. Growers in the SE can use CT techniques by using strip till because it is compatible with cotton and peanut production (Pudelko et al., 1995, 1997).

	INCLUSION OF FORAGE GRASSES IN THE PEANUT–COTTON ROTATION

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Soil Physical Properties
Perhaps the biggest benefits of including perennial grasses in the traditional peanut–cotton rotation are derived from improved soil quality (Reeves, 1997). Perennial grasses can be grown under environmental conditions that are less than ideal for many agronomic crops. Perennial grasses can thus be used to conserve soils under unfavorable environmental conditions including drought or excess moisture and to improve soil conditions before less robust annual crops are grown. The wide range of grasses that have been used for different soil conditions include drought and salt tolerant wheatgrass (Agropyron spp.) and flood tolerant reed canarygrass (Phyalaris spp.) (Entz et al., 2002). Adapted perennial grasses generally develop a deep rooting system which can improve soil conditions. Pavlychenko (1942) noted that native grasses such as porcupine grass (Stipa spartea Trin) and blue grama [Bouteloua gracilis (Willd. ex H.B.K.) Lag. ex Griffiths] were more effective in improving soil structure at depths of 60 cm than a popular introduced crested wheatgrass [Agropyron cristatum (L.) Gaertn]. In this review we focus on the perennial grass bahiagrass because it is adapted to the SE. Bahiagrass is traditionally grown as a pasture grass, hence it is not new to most farmers. It grows better than a number of other grasses because it is drought tolerant and can be grown on a wide range of soil types including sandy soils (Field and Taylor, 2002). Bermudagrass is equally adapted in some sections of the SE and can be used instead of bahiagrass.

In the SE, much of the farmland suffers from a natural compaction layer starting at 15- to 20- cm depth and continuing to 30 cm (Kashirad et al., 1967; Campbell et al., 1974). The compaction confines root development to a shallow soil volume and consequently has a major, adverse effect on crop management. The resultant shallow-rooted crops become susceptible to even the smallest amount of moisture stress in the sandy soils typical of the SE. Perennials including bahiagrass and bermudagrass develop a deep root system which penetrates through the compaction layer (Elkins et al., 1977). When the roots die, they decay and leave root channels which impart many positive attributes to soil structure and health (Elkins et al., 1977; Wright et al., 2004). Long and Elkins (1983) compared cotton following 3 yr of continuous bahiagrass sod and continuous cotton. They found a sevenfold increase in pore volume of sizes >1.0 mm in the dense soil layer below the plow depth. They concluded that the dense soil layer had been penetrated by the bahiagrass roots and that, after the decay of the roots, pores were left that were large enough for the cotton roots to grow through.

Perennial grasses including bahiagrass and bermudagrass can reduce the need for irrigation in the following crop. Elkins et al. (1977) calculated that given an evapotranspiration rate of 0.85 cm of water per day, available water of 1 cm per 12 cm of soil, and plant rooting depth of 15 cm, plants will experience water stress after only 3 d without rainfall. However, if the rooting depth was 152 cm, the plant would not experience water stress until 30 d after rainfall (Table 1) (Elkins et al., 1977). Using weather data from Ward et al. (1959), Elkins et al. (1977) determined that for the average Coastal Plain Soil (for the most part a coarse-textured sandy soil with low water-holding capacity), a crop with a rooting depth of 30 cm will experience 60 drought days from May through August in 5 out of 10 yr. However, if rooting depth were 152-cm deep, the crop would experience only 11 drought days. Cropping systems that increase rooting depth and reduce the need for irrigation are essential for water conservation.

View this table: [in this window] [in a new window]   Table 1. Days without plant water stress following rainfall for dif-ferent rooting depths.

Organic Matter
Soils in the SE are generally infertile and lower in OM compared those in much of the USA. Continuous row cropping for hundreds of years in many instances has further degraded these delicate soils. Organic matter impacts numerous soil quality factors including improved soil aggregation, water infiltration, acting as a store house for slow release of nutrients and providing substrate to be used by soil fauna including the wide array of microbes and earthworms (Lumbricus terrestris). There has been a progression toward larger and heavier farm machinery in recent years. The heavier machinery can exacerbate compaction problems including the sandy SE soils. Soil OM enables soils to absorb compaction from tillage and harvest equipment (Wilhelm et al., 2004). Historically, agricultural practices that used conventional tillage depleted soil OM, leading to loss in soil productivity. Before intensive farming systems were adopted, native perennial grasses once conserved the soil OM in the former tall prairie grass areas of the USA. The soil OM content was around 4% when it was first plowed out of the native prairie grass and has decreased over the past 100 yr to 1 to 2% through continuous cropping and tillage (Boman et al., 1996). The loss of OM has resulted in the loss of farmers and farmlands (Wright et al., 2003).

Historically, forage legumes have provided more benefits to soil quality and crop yield in the short term than perennial grasses, however, they are not as adapted to the SE where, due to high humidity, they become prone to disease (Gates, 2003). Numerous articles indicate that legumes can immediately increase available N, due to their rapid breakdown and release of N (Vyn et al., 2000; Holderbaum et al., 1990; McVay et al., 1989). Legumes, however, contribute little to long-term build up of soil OM (Frye et al., 1985). In addition to preventing soil losses, the CRP has resulted in increases in OM in the Great Plains (Gebhart et al., 1994). However, the CRP has not always been popular with growers since it takes away farmland that is in close proximity to their farm.

Building up OM levels is a long-term process. Even when the best conservation measures are practiced, OM levels increase at a slow rate of only 0.1 to 0.2% per year (Martin, 2003). Therefore, proper management strategies to prevent soil organic matter depletion should be of foremost importance. Inserting perennial grasses in cropping systems is a favorable and cost-effective way to increase and retain soil OM.

Soil Fauna
Numerous articles cite positive relationships between increased abundance and diversity of soil fauna and soil quality and crop productivity. Soil fauna are responsible for a multitude of soil processes including decay of OM, cycling of nutrients, regulating micro flora through predation, reduction of pest species through predation, breakdown of agricultural chemicals, improvement of soil aggregation, aeration, and water infiltration (Santos and Whitford, 1981; Tabatabai, 1994; Gupta and Yeates, 1997; Doube and Schmidt, 1997; Phelan, 2004; Kennedy et al., 2004). Soil microclimate and niche diversity influence species composition of the soil fauna (van Straalen, 1997). Composite mixtures of plant species favor more microclimates, provide a wider choice of food resources and niches to support a wider faunal species composition (Coll and Bottrell, 1995; Dicke, 1999). Consequently, all agricultural management practices, including the choice of cropping systems, and land preparation, will influence microclimate and hence soil faunal populations (Pankhurst, 1997; Doran and Smith, 1987; Berry and Karlen, 1993; Pankhurst et al., 1995; Kennedy et al., 2004). Diverse crop rotations and reduced tillage are generally believed to increase the number of beneficial soil fauna (Krupinsky et al., 2002; Olfert et al., 2002). Studies have shown an increase in some arthropods and spiders (Blumberg and Crossley, 1983) and ground beetles (House and All, 1981) under CT. Acosta-Martínez et al. (2004) reported higher protozoa and fungi in crop–livestock rotations compared to continuous cotton. The authors further concluded that the higher protozoa and fungal densities indicated healthier soil and sustainability of the integrated crop–livestock system compared with continuous cotton. In addition to higher productivity, diverse systems have greater resistance (ability to withstands environmental stresses) and resilience (ability to recover from environmental stresses) (Giller et al., 1997; Wolters, 1997; Nicholls and Altieri, 2004). A diversified sod-based bahiagrass–cotton–peanut cropping system under CT would be expected to result in rich species compositions of soil flora and fauna. The species composition would be even richer if the sod-based peanut–cotton cropping system was coupled with livestock production. Several articles report greater arthropod species diversity in organic farming compared to conventional farming (El Titi and Ipach, 1989; Moreby et al., 1994). A major reason for this is because organic farming maintains high levels of fresh organic matter (Phelan, 2004). Likewise, reduced tillage has more soil dwelling anthropods because of higher organic matter compared to conventional tillage (Olfert et al., 2002). A sod–livestock cropping system would be expected to have higher levels of organic matter, and consequently, improve soil fauna richness. While very little literature exists on the agro-ecological roles soil fauna play in cropping systems (Freckman, 1994; Turco et al., 1994), even less is known about their roles in new cropping systems such as the sod-based peanut–cotton–livestock production system.

A group of organisms which has found use in cropping systems as indicators of soil quality and hence sustainability of cropping systems are earthworms. The abundance of earthworms is often correlated with numerous positive soil quality attributes. Earthworms increase aggregate stability (Hopp and Hopkins, 1946), increase soil water infiltration (Trojan and Linden, 1992; Bowman, 1993; Katsvairo et al., 2002), increase the water-holding capacity (Stockdill, 1982), reduce surface crusting (Kladivko et al., 1986), and provide burrows which enable root growth and gaseous exchange. These burrow walls are nutrient rich, thus enhancing nutrient uptake and root growth (Kladivko and Timmenga, 1990; Zachmann and Linden, 1989). Earthworms have the potential to improve compacted soil structure (Lamgmaack et al., 1999) and increase soil aeration (Magdoff and van Es, 2000). Through feeding and burrowing activities and metabolic activities such as excretion and mucus production, earthworms can contribute and cycle nutrients including N and incorporate organic residues and amendments into the soil (Parmelee and Crossley, 1988; Curry et al., 1995; Mackay and Kladivko, 1985; Kladivko et al., 1986). Earthworm castings have also been shown to provide plant growth responses above that of the level of nutrients in the castings (Arancon et al., 2003). Recent findings have shown that the lining of the earthworm channels contain material which enable nitrates and pesticides to be immobilized (Arancon et al., 2003).

Earthworms are sensitive to agricultural management practices including tillage, crop rotations, and pesticides. Numerous studies show that the many forms of CT increase earthworm population densities over conventional tillage. Jordan et al. (1997) compared earthworm densities across several crop rotations and tillage systems. They concluded that tillage was the single most important factor which influences population densities, with no-till having the highest earthworm densities. In another study, Berry and Karlen (1993) showed that the number of earthworms decreased with increase in tillage frequency. Conservation tillage increases plant surface residues, which in turn provides food for the earthworms. Conventional tillage, on the other hand, accelerates decomposition of plant residues and also disrupts earthworm channels. In addition to plant residues, temperature and moisture are also factors that affect earthworm population densities, and both these factors are influenced by tillage practices (Berry and Karlen, 1993).

Very few articles report on the effects of bahiagrass on earthworms in sod-based peanut–cotton cropping systems (Hartzog et al., 2005; Wright et al., 2004). Other studies have shown that crop rotations which increase plant residues and OM also increase earthworm population densities (Katsvairo et al., 2002). We expect that a diverse cropping system, which includes bahiagrass in the peanut–cotton rotation, would increase plant residues. As shown in previous sections, perennial grasses on their own increased soil OM. Also, growing both peanut and cotton after bahiagrass results in greater biomass from these crops (Katsvairo et al., 2005; Katsvairo et al., 2004b). This too increases the amount of plant residues available for earthworms. Hence, an increase in earthworm population densities would be expected in a diverse rotation which includes bahiagrass. Preliminary studies from Florida and Alabama have shown higher earthworm densities in peanut and cotton after bahiagrass and tall fescue (Festuca arundinacea Schreb.), (Wright et al., 2004).

	WATER QUALITY

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Nitrogen Leaching
The formerly tall-grass prairie region was largely converted to annual cropping in <150 yr (Glover, 2003). Higher rates of N fertilization are generally used on row crops compared to those used on perennial grasses; subsequently NO₃ leaching can be a major problem in row crop production. Most of the N originates from cropped areas and ends up either in groundwater or surface water bodies. Faeth (2000, p. 5–6) reported that 48 and 37% of nonpoint N and P, respectively, in surface waters originates from annual croplands. Nitrate leaching is more problematic in sandy soils, typical of the SE, because of its high solubility and mobility. A significant number of wells in the USA have NO₃ levels greater than the USEPA maximum contamination level for drinking water of 10 mg L^–1 (USDA, 1991). One of the worst examples of NO₃–contaminating water bodies is the hypoxia of the region of the Gulf of Mexico. Since the 1950s, NO₃ influx into the Gulf has increased by 300% (Rabalais et al., 2002). This heavy NO₃ load causes algal blooms, which exhaust oxygen and eventually lead to dead zones (Rabalais et al., 2002). The primary cause of the problem has since been traced back to conversion of native vegetation to annual cropland within the Mississippi River Basin (Rabalais et al., 2002).

The enforcement of the 1972 Clean Water Act through the Total Maximum Daily Load program, more environmental awareness, government incentives, and fear of lawsuits prompts growers to implement more agricultural practices which could successfully reduce N contamination to the environment. A simple way to reduce N leaching is to reduce application rates, but many farmers fear yield reductions. Historically, the need to guarantee higher yields coupled with the relatively inexpensive price of N fertilizers often caused farmers to apply N at rates greater than crop needs (Hutmacher et al., 2004; Bell et al., 2003). Sexton et al. (1996) showed that very high rates of N caused an exponential increase in N leaching to groundwater.

Growing crops in rotation is an effective way to improve nutrient use efficiency and reduce N leaching. Rotated crops should have different rooting and growth patterns and N demand (Grant et al., 2002). If deep rooted crops such as perennial grasses are included in rotations with shallow rooted crops, the deep rooted crops can scavenge and extract nutrients including N from deep soil profiles and recycle the nutrients that would otherwise have been lost. Also, as described earlier, crops grown after perennial grasses are often more deeply rooted than if they had been grown in continuous cropping. This means subsequent crops after bahiagrass may also extract more N and reduce N-leaching losses. Long and Elkins (1983) found that NO₃–N in the soil solution at 170-cm depth was only 10 mg L^–1 in plots following bahiagrass, but 40 mg L^–1 in plots under continuous cotton (112 kg N ha^–1 was applied to the cotton crop). In Florida, Katsvairo et al. (2004a) conducted lysimeter studies and reported reduced soil water NO₃ and ammonium in cotton grown after bahiagrass compared to cotton in the traditional peanut–cotton rotation. In related reports from the same study, the authors documented extensive rooting systems, greater plant biomass, increased leaf area index and nutrient uptake, including N uptake, in the sod-based rotation compared to the conventional system (Katsvairo et al., 2004b, 2005). It seems likely that the reported reduction in soil water N could have been a result of greater N uptake from the cotton when grown after the sod. In Mississippi, a common practice is to reduce N rates by as much as 20% when cotton follows either corn or sorghum (M.W. Ebelhar, personal communication, 2005). The residual N from the N applied for either the corn or sorghum, makes significant contributions to the cotton, a crop which does not require as much N. Reducing N application even by small amounts can have far-reaching positive effects. Sexton et al. (1996) showed that when N application rate was reduced by a mere 5% of the required amount for maximum corn yield, NO₃ leaching was reduced by up to 45%.

Phosphorus Considerations
Phosphorus loading is a major environmental concern, with agriculture making a significant contribution to the P in fresh water bodies. Phosphorus accelerates eutrophication, adversely affecting water quality (Sharpley et al., 1994; U.S. Environmental Protection Agency, 1996). An example of a lake adversely affected by eutrophication is Lake Okeechobee in Florida, the largest body of fresh water in the SE (Lake Okeechobee Annual Report, 2004). While concentrations of P as low as 0.02 µg L^–1 can accelerate eutrophication, P concentrations at Lake Okeechobee are elevated up to 120 µg L^–1, causing numerous ecological, aesthetic, and economic problems (Sharpley et al., 1993; LakeOkeechobee.org, 2005). Similarly, eutrophication problems as a result of high P levels are also experienced at Lake Opopka, another Florida Lake. Old practices of repumping water back into Lake Okeechobee following furrow irrigation plus erosion are the main causes of the elevated levels of P. In preceding sections we showed that cultural practices such as CT reduce soil erosion, and likewise we also showed that perennial grasses introduced into cropping systems reduce soil erosion. Our data show greater water infiltration rates for the sod rotated cotton compared to conventional cotton (Wright et al., 2004). High infiltration rates reduce runoff losses. We would, therefore, expect that the sod-based peanut–cotton cropping system would reduce P contamination to fresh water bodies.

	PEST MANAGEMENT

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Aboveground Fauna
The need to reduce pesticide loading to the environment resulted in the development of IPM. The beauty of IPM is its attempt to pull together all available tactics to manage disease and pest densities at acceptable economic threshold levels with reduced risk to people and the environment, with emphasis on cultural and biological controls (IPM Roadmap, 2004). Appropriate cropping systems are an important component of IPM because the cropping systems can influence the survival and success of both beneficial and pest organisms (Altieri, 1994; Nicholls and Altieri, 2004). Stary and Pike (1999) reported that the diversity of beneficial natural arthropods is closely linked to availability of natural habitats. A range of habitats can increase survival of natural enemies by providing a wider resource range and refugia (Olfert et al., 2002). In the preceding pages we showed that tillage disrupts dwelling places for arthropods, and limited rotations support fewer soil fauna. It comes as no surprise that conventionally-tilled agricultural fields would have few natural habitats for beneficial arthropods. By incorporating sod into the peanut–cotton cropping system, the system more closely resembles a native system and could provide a wider range of habitats and food for beneficial natural enemies. With the increase in available habitats, we expect an increase in the number of natural enemies in the sod-based cropping system which would in turn reduce the need for chemical sprays, along the same goals as IPM. The use of natural enemies to control pests is attractive because it is cost effective, safer for humans, and friendlier to the environment (Olfert et al., 2002).

Weed Considerations
The process of changing from a simple and short-cycle rotational system to a complex multi-crop long rotation may cause weed species shifts, which could be more or less detrimental than the ones they replace (Derksen et al., 2002). We expect the perennial grass rotation to help ameliorate weed problems in crops because in general, diverse cropping systems allow better weed control through the use of broader spectrum of herbicides than simpler rotations (Patterson et al., 1996; Reeves et al., 1996; 1997). Including perennial grasses in rotations provides for longer periods between crops and can effectively break the lifecycles of weeds that mimic the crops (Anderson, 1997; Patriquin, 1988). Once established, perennial grasses are usually competitive and can suppress weed growth. Kalmbacher (1980) reported that bahiagrass suppressed weed encroachment, while Kegode et al. (1999) reported a reduction in weed seed production with perennial grasses. In the case where perennial grasses have slow rates of establishment, and weed control is a major issue during the early stages of establishment, the perennial grasses can be grown in conjunction with other species such as pearl millet [Pennisetum americanum (L.) Leeke], German millet [Setaria italica (L.) Beauv.], and small grains (Wright et al., 1978). These species have aggressive to intermediate rates of establishment. Once the perennial grasses are established, the other species can be mowed down, leaving the perennial grasses to dominate. Diverse cropping systems, as in the case of the bahia–peanut–cotton cropping system, have more surface plant residues which can suppress weed growth. The potential for weed suppression is even greater if a burn down herbicide is used on the perennial grass and the subsequent crop is grown under CT. A combination of multiple factors including improved soil structure and efficient utilization of resources can cause subsequent crops after perennial grasses to develop more quickly and rapidly produce a canopy which shades weeds. Rapid canopy development and early season weed suppression has been reported for cotton and peanuts after bahiagrass (Katsvairo et al., 2004b).

Diverse cropping systems support a wider spectrum of weed species (Derksen et al., 1995; Froud-Williams, 1988). Simultaneously, diverse speciation reduces the predominance by any one weed type (Liebman and Dyck, 1993; Anderson, 1998; Derksen et al., 1995). However, if the weed pressure is high, a more diverse weed population may call for more than one type of herbicide, thus increasing herbicide costs. A diverse rotation system spaces out the crops and allows growers to rotate herbicides with different modes of action. This can delay and may prevent the onset of herbicide-resistance in weeds (York and Culpepper, 2004).

	CROP YIELDS

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
The yields for most row crops have been stagnant since the 1990s in the SE (USDA, 2004a). In 2002, the official state peanut yields in Alabama were estimated to be at or below the cost of production on the average peanut farm (Hartzog and Balkcom, 2003). Sod-based rotations can increase crop yields. Including bahiagrass in the rotation increased peanut yields in Georgia and Florida (White et al., 1962; Dickson and Hewlett, 1989). Rotations which included even 1 yr of bahiagrass increased peanut yield (Norden et al., 1980), but yields for the subsequent crops were greater, the longer the field was under sod (Hagan et al., 2003). In a Brenneman et al. (1995) study (Table 2), peanut yields were 4443, 4792, and 4547 kg/ha following the first, second year and third year of bahiagrass, respectively. Norden et al. (1980) reported that peanut showed improved yield for up to 5 yr when preceded by a long term bahiagrass rotation. In another study, Brenneman et al. (2003) reported that the positive rotational effects lasted only 2 yr, after which the yields were similar to continuous peanuts. The yield increases in peanuts due to crop rotations have been attributed to reduced pest populations. Sholar et al. (1995) and Taylor and Rodriguez-Kabana (1999) reported that in rotations, perennial crops are more effective in controlling peanut soil-borne diseases than cotton. The National Cotton Council of America (2005) attributed 4.39% of cotton losses to nematodes in 2000. Rodriguez-Kabana et al. (1988) reported densities for root-knot (Meloidogyne arenaria) juveniles at harvest to be up to 98% lower for bahiagrass rotated peanuts, compared to continuous peanuts, and this increased yield by up to 27%. Rodríguez-Kábana et al. (1988) reported that root-knot (M. arenaria) populations remained low during the entire growing season in Alabama, reducing populations by 41% in peanuts following only 1 yr of bahiagrass as compared to plots in continuous peanuts. After 2 yr of bahiagrass, Rodríguez-Kábana et al. (1991) found that root- knot (M. arenaria) populations were reduced to non-detectable levels and recorded an increase in soybean (Glycine max (L.) Merrill) yields of 114%. In Florida, Dickson and Hewlett (1989) reported reduced population densities of the root-knot nematode (M. arenaria) in peanuts early in the growing season following 1 yr of bahiagrass, however, the nematode population level reverted to high levels at the end of the season. Nonetheless, they still observed a 2.3-fold increase in peanut yield following 1 yr of bahiagrass. Johnson et al. (1999) reported a reduction in limb rot (Rhizoctonia solani Kuhn) and stem rot (Scerotium rolfsii Sacc.) in bahiagrass rotated peanut compared to continuous peanuts. Studies from Florida and Alabama also show that the improved peanut yields following bahiagrass are also attributable to improved soil conditions. Bahiagrass increased earthworm population densities, infiltration and soil water retention in peanuts and cotton fields (Wright et al., 2004; Katsvairo et al., 2004a).

View this table: [in this window] [in a new window]   Table 2. Influence of bahiagrass rotations treatment on peanut yield, 1990 to 1993.

As with cotton yields, little or no literature documents bahiagrass yields in peanut/cotton cropping systems. Bahiagrass yields up to 13.44 t ha^–1, and yield can be greater than tall fescue (Festuca arundinacea Shreb.), the most widely used pasture crop in the USA, and smooth bromegrass (Bromus inermis Leyss.), the most used cool-season grass (Field and Taylor, 2002). Its nutritional value, including crude protein (CP), acid detergent fiber (ADF), and neutral detergent fiber (NDF) values are comparable to other grasses (Field and Taylor, 2002). Bahiagrass can be grazed, harvested for seed or hay.

In the SE, peanut and cotton farmers often grow a winter cover crop immediately after harvesting the major row crop. Cover crops are used for winter grazing and to prevent soil erosion, increase soil organic matter and improve soil water retention (Schertz and Kemper, 1994; Bradley, 1993; Nyakatawa et al., 2000; Nyakatawa et al., 2001b; Dabney et al., 2001; Baughman et al., 2001). Cover crops also utilize the residual soil nutrients including N from mineralization of organic matter and reduce leaching losses to groundwater (Brandi-Dohrn et al., 1997; Logsdon et al., 2002). Because cover crops can be drilled directly into winter killed bahiagrass, use of perennial grasses fits with the tradition of using cover crops.

	INTEGRATING LIVESTOCK INTO THE PEANUT–COTTON CROPPING SYSTEM

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Historical Trends in Cattle Production and Implications for Livestock Integration
Cattle were first introduced to the US, initially in Florida in 1513 by Ponce de Leon (Florida Cattlemen's Association, 2005). Unwelcome, the Spanish explorers met stiff resistance from the Caloosa Indian warriors and retreated back to their ships after a battle. It is not clear whether these cattle survived and became the first cattle to range wildly in Florida. The combined number of beef and dairy cattle in the US has fluctuated over several hundred years and reached a record high of 131.8 million head in 1975 (Field and Taylor, 2002). Of that total, the Tri-States (Alabama, Florida and Georgia) had 8.70 million head of cattle (USDA, 2005a). A steady decline in number of cattle followed thereafter. By the year 2004, the total head count in the US was 94.9 million, while the total for the Tri-States was 4.35 million (USDA, 2004b; USDA, 2005a; USDA, 2005b). In the early to mid-1980s, land value decreased by up to 60%. Heavy debt load on purchased land, coupled with the fact that creditors only provided capital for operations which were making profit, forced many cattle producers to sell out. The period 1975- 2004 also saw several fluctuations in cattle prices (Field and Taylor, 2002). To date, farms that had owned cattle for generations removed their fences or allowed them to collapse (Krall and Schuman, 1996). Some may have held onto cattle to utilize land and/or products unsuitable for other purposes or as a sort of non-interest bearing savings account. Also, the current generation of farmers likely did not grow-up around or have experience with cattle (except maybe a show steer), or feel that they are too old to make the long term commitment required. The cultural challenge may be as large as the economic challenge. However, the potential lucrative returns from this rotation (as shown in the Economics section) could make current farmers willing to learn to produce cattle.

	BENEFITS AND CHALLENGES OF INCORPORATING CATTLE INTO THE PEANUT–COTTON ROTATION

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
It is often said history goes in cycles. The early farmers had intricate links between livestock and crop production, a system sometimes referred to as mixed farming. The same practices are still used by subsistence and small family farms in many countries today. With increasing emphasis on commercial farming, there was a move toward specialization (Powell et al., 2004). However, with market fluctuations and emphasis on environmental awareness, there is a new movement back to diversified crop/livestock enterprises. Diversified cropping can provide a buffer against unpredictable weather, such as droughts and hurricanes. A good example is the four major hurricanes that swept through the SE, particularly Florida in 2004. While all four hurricanes caused economic damage to crops at different stages of growth, hurricane Ivan severely impacted Florida, Alabama and Georgia cotton during the boll opening stage, and as a result, a number of farmers lost a large part of the cotton crop. If a grower had most of their farm in cotton, they would have lost most of their income. On the other hand, if a grower had some section of the farm under bahiagrass, the bahiagrass would have survived the hurricanes. Diversified cropping systems also reduce economic risks by reducing yearly variations in returns, thus further reducing reliance on government programs (Sod Report, 2005; Krall and Schuman, 1996). In the economics section we show how incorporating livestock into the farming system increases the overall farm profitability.

The National Cattlemen's Beef Association (2004) and Field and Taylor (2002) cite numerous advantages for cattle farming. Row crop farmers too, can take advantage of these benefits if they integrate cattle into their cropping. Below are some of the advantages of grazing cited by the National Cattlemen's Beef Association (2004) and Field and Taylor (2002): prevention of forest fires, control of unwanted vegetation, utilization of plants that cannot be digested by humans, and efficient use of renewable resource i.e., from low-energy grass to high-protein beef.

Bird et al.'s (1995) survey report showed that up to 95% of sustainable farms in four states in the USA had livestock compared to a mere 37 to 58% for conventional farms. A sustainable farm is defined as one which "gives back as much to the land and people as it receives. It seeks independence from non-renewable resources, it minimizes pollution, takes steps to care for the environment, and cares for its employees" (Coffeeresearch.org, 2006). Reasons for including livestock in the rotations included additional weed control through grazing, and higher income from cattle through intensive grazing and winter grazing land that had summer crops. Keeping livestock also provided a cushioning effect in the case where grain which did not attain marketable quality because of weather related reasons could still be fed to livestock.

The ever expanding human population has reduced wildlife habitat. If wildlife populations are going to be sustained, it will be necessary to provide wildlife habitat within agricultural landscapes. Including livestock in cropping systems increases the proliferation of wildlife. The National Cattlemen's Beef Association (2004) reports that ground nesting birds, small mammals and deer (Odocoileus virginianus) find dwelling places in pastures. Ball et al. (1996) documented that the same plant species often grown for livestock in the southern USA are also grown for game animals. Deer, wild turkey (Meleagris gallopavo), and rabbits (Oryctolagus cuniculus) all consume green material. Diverse plants are likely to attract insects, which will in turn attract birds.

In addition to higher returns and environmental stewardship, integrated cropping systems can achieve aesthetic beauty resulting in inner peace for the farmers and surrounding community. Ball et al. (1996) suggested that there is "something restful, peaceful and satisfying in watching animals graze." This is evident in the thousands of pictures and paintings over the centuries which depict pastoral sceneries (Ball et al., 1996). Likewise, pastoral music dates back hundreds of years. Diverse rotation will enable farmers and communities to achieve this artistic beauty.

Incorporating bahiagrass–livestock into the peanut–cotton rotation can help sequester C. Estimates show that widespread adoption of pasture-based rotations with CT row crops in the SE could sequester from 13 to 29% of the estimated C potential in the USA (120–270 Tg of C) (Causarano et al., 2005). Cropping systems designed to sequester C could also reduce nutrient losses to the environment by 40 to 60% and provide additional potential for participation in environmental trading programs (Causarano et al., 2005).

Integrated farming systems include capability for the components of the system to support each other, and capture additional synergistic effects. In the case of the proposed livestock integrated peanut–cotton cropping system, the bahiagrass can be baled and fed to the cattle, or alternatively, the cattle can graze on the bahiagrass. As part of the rotational scheme, cattle can graze on the winter small grain crops. In winter, small grain crops could potentially be grown on land which would be used for peanut and cotton in summer, thus increasing the available pasture land for a higher carrying capacity. Winter cover crops are grown at a time of the year when fewer pests are present. The winter climate of the SE is usually mild with few droughts or floods. Livestock manure from the grazing cattle provides nutrients and other beneficial properties important to soil quality. Gates (2003) reported that livestock manure can increase soil OM content, while Brouwer and Powell (1995; 1998) showed that manure and urine can raise the pH level and accelerate the decomposition of OM. We elaborated on the importance of OM in previous sections.

The on-farm integration of crop and livestock systems is challenging as it requires new knowledge and greater management skills. Most farmers tend to be either good row crop farmers or livestock producers. Hardesty and Tiedeman (1996) pointed out that the safety of some chemicals used on crops has not been determined for livestock. Crops and livestock enterprises can also compete for scarce resources including land and labor. A recent drop in grain crop prices in Argentina prompted farmers to rebuild their cattle herds on the land which decades ago was in pastures but was recently in field crops. The farmers encountered competition for land between the two enterprises, making it difficult to return to livestock production (Arzadun et al., 2003).

More potential downfalls exist in having livestock in integrated cropping systems. Grazing by cattle can cause soil compaction which in turn can reduce water infiltration and increase soil bulk density. Profitt et al. (1993) showed that animal hooves can exert pressures as high as 200 kPa. Compaction on the other hand is a function of soil texture and moisture, grazing intensity, vegetation and climate (Taboada and Lavado, 1993). Studies from Alabama have shown that animal grazing causes compaction mostly in the top 15 cm of the soil, but little below that depth (Katsvairo et al., unpublished data, 2004). Krenzer et al. (1989) and Worrell et al. (1992) both reported an increase in soil compaction on the subsequent winter wheat as a result of grazing. Increased compaction could have partially caused the crop yield reduction they observed. On a silt loam soil in Alabama, Mullins and Burmester (1997) observed a reduction in cotton yield in 2 of 3 yr after grazing a wheat cover crop. Abdel-Magid et al. (1987) reported an increase in bulk density in the 0- to 5-cm depth due to cattle grazing in 1 of 2 yr.

Other researchers have shown that the damage due to animal compaction is minimal and short lived. Twerdoff et al. (1999) found that the bulk density increase on loamy soil as a result of animal treading was lower in perennial pastures compared to annual pastures. Mapfumo et al. (1999) reported that cyclical perturbations such as wetting and drying and earthworm activities can alleviate the impacts of compaction. Russell et al. (1999) reported an increase in soil bulk density and surface roughness after grazing corn residues, however, this did not decrease the subsequent soybean yields in a soybean–corn rotation. Siri-Prieto et al. (2003) observed an increase in compaction in the 10- to 15-cm depth as a result of grazing but concluded that conventional tillage or CT with noninversion deep tillage can reverse and negate the problem.

Cattle manure may be substituted for chemical fertilizers. In addition to providing plant nutrients, animal manure provides physical, chemical, and biological benefits to the soil beyond that of inorganic commercial fertilizers (Hatfield and Cambardella, 2001). In pastures, cattle feces can be an important source of nutrients. However, not all the deposited nutrients are taken up by plants and can be a source of nonpoint-source pollution and hazardous to the environment (White et al., 2001). Nonetheless, pasture-based cattle systems require less-expensive manure management systems compared with confinement dairy farms (White et al., 2001). In fact, Naylor et al. (2005) further points out that delinking crop and livestock production systems increases both N and P runoff.

	ECONOMICS OF THE CROP–LIVESTOCK SYSTEM

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Economics is the dominant factor determining adoption of new farming systems (Wesley et al., 1995). It can be generalized that in the past most growers strived to obtain maximum returns. Recently there has been a move to accept optimum economic returns if the production process helps maintain environmental quality (Zentner et al., 2002). The economics of a sod rotation compared to an annual cash crop system can be complicated to determine and must be considered over multiple years. Income can be lost when the area allocated to the most profitable crop is reduced, however, expenses can be reduced if the rotation crop requires fewer inputs. Furthermore, the rotation crop usually improves the growth of the main cash crop and results in higher yields. In previous sections and in Fig. 1 , we showed that both peanut and cotton grown after sod in rotation show more plant growth and better yield and are better able to withstand disease, weeds, and insect pest pressure. We developed an interactive business model to evaluate the economic feasibility of a 4-yr livestock–peanut–cotton–sod rotation. The model is located at http://nfrec.ifas.ufl.edu/sodrotation.htm (verified 10 May 2006). Because it is an interactive model, farmers can input values that simulate their farm scenario. We chose an 80 ha farm as the working size model because it is an appropriate size which first time farmers may find economical for small equipment and limited labor supply. We assumed that for an 80 ha farm, 20 ha would be under first year bahiagrass, 20 ha under second year bahiagrass, 20 ha under cotton, and 20 ha under peanuts. We show an example of our business model as Table 3. In the example, the field stays the same while crops and livestock are rotated. The net returns at the beginning of the rotation are lower compared to the traditional peanut–cotton rotation. However returns can be two- to sixfold in Year 3 and three- to sixfold greater in Year 4 compared to the conventional peanut–cotton rotation (Table 3). The low profits at the beginning of the rotation stem from the establishment costs for the bahiagrass while the greater returns in Years 3 and 4 are from the cattle revenue and greater revenue from crops with higher yields. However, in an actual 40 ha area with this rotation in Florida, cattle were able to graze first year bahiagrass throughout the season. In this example, we postulate that a grower can carry 76 head of livestock (38 cow per calf pairs) on the 20 ha of 2-yr-old bahiagrass as well as 20 ha of 1-yr-old bahiagrass. Research from Florida shows that up to 38 cow per calf pairs can be sustained on a 20 ha bahiagrass pasture with some grazing on first year bahiagrass (J.J. Marois et al., unpublished data, 2004) plus winter grazing. Another critical aspect of the sod-based rotation is the increase in yield for both peanut and cotton following the sod. Even if the grower does not have cattle but used the sod rotation, the sod-based rotation would still be more profitable than the conventional peanut–cotton rotation, because of the higher crop yields from the rotation. In addition, bahiagrass hay or seed can be sold for extra income. Many of the small row crop farmers in the southeastern USA have small cattle herds (<100 head), and they usually buy hay from their neighbors. Farmers with limited capital and infrastructure can still incorporate livestock into their rotations through contract grazing of cattle and gain extra income without penalizing the main crops (Siri-Prieto et al., 2003). Bransby et al. (1999) showed that contract grazing of stocker cattle on a short-term basis (winter grazing) can achieve returns between $173 to $556 ha^–1.

View larger version (25K): [in this window] [in a new window]   Fig. 1. Conceptual model of benefits accruing from integrated livestock peanut–cotton farming systems and their interactions.

Despite the apparent increase in profits in the long run, adoption is expected to be slow for the sod rotation cropping system. Currently only 2% of the peanuts produced in Florida are preceded by bahiagrass. Also about 80% of the land under peanut and cotton in Florida is rented and the majority on a yearly basis. Growers are thus forced operate based on short-term economic gains and not for long term. However, as growers learn that profits can be higher in mixed crop–livestock systems requiring that less than half the acreage be in crops, adoption of the system should increase.

	CONCLUSION

TOP ABSTRACT INTRODUCTION CONSERVATION TILLAGE INCLUSION OF FORAGE GRASSES... WATER QUALITY PEST MANAGEMENT CROP YIELDS INTEGRATING LIVESTOCK INTO THE... BENEFITS AND CHALLENGES OF... ECONOMICS OF THE CROP-LIVESTOCK... CONCLUSION REFERENCES

 
Numerous factors could interact to bring about the positive outcome for implementation of the sod-based livestock cropping system. This review shows the many soil quality and pest management benefits associated with this system and the resulting expectations of improved plant development. We depict a conceptual model for the sod-based livestock cropping system as Fig. 1. While the overall system complexity may appear daunting to growers, our experiences have shown that growers do not necessarily have to work hard to improve the soil quality or plant physiological development or pest management or even keep track of all the detailed activities occurring in the farming system. Once the major steps are implemented to integrate the sod with row crops and livestock, the synergistic effects falls in place, more like the old saying "take care of the pennies and the dollars will take care of themselves." This, however, is not to say one should not keep an eye open for challenges.

The crop–sod–livestock rotation, particularly under CT, shows great potential for the SE. Conservation tillage reduces production costs and improves soil and water quality. Inclusion of perennial grasses in the cropping system adds to the benefits accruing for the implementation of CT alone and should further enhance soil and water quality. A sod-based rotation should reduce reliance on irrigation, pesticides, and the reduction in row-crop hectares should reduce the need for large equipment. Crop yields after perennial grasses are increased. Cattle diversify marketable products and create an alternate source of crop utilization, while reducing overall risks compared to farming operations based solely on row crops. Development of an effective sod-based livestock integrated cropping system is an economically and ecologically viable alternative to the current peanut–cotton cropping system. Sod-based rotations are applicable to a wide range of soil types, are an effective practice to control plant–parasitic nematodes and plant diseases, and reduce overall pest problems. By increasing farm profitability by two- to sixfold, this system could also help improve rural economics. Researchers in the tri-states (Alabama, Florida, and Georgia) are currently conducting cooperative work to test the viability of the crop–sod–livestock enterprise. This extensive research evaluates soil quality, plant development, weeds, insects, and disease, yield and livestock performance and economics in the new cropping system. To date, soil quality, plant development, yield, disease and pest control, and economic returns data from this multi-state study have been positive and encouraging. We are seeing positive ripple effects within the system where the positive effects of bahiagrass on soil quality are resulting in plants with higher growth rates and ability to better withstand environmental stresses. Improved growth is translating into higher yields with reduced usage of pesticides. The effects cumulate to create higher economic returns compared with monocultures. Much remains unknown, and hence, there is the need for more research. The performance of the cotton and peanut in rotation with perennial grasses under different environmental conditions to include different rainfall regimes and different soil types is largely unknown. Most of the management techniques currently used in the management of the sod-based livestock–cropping systems are derived either from cotton, peanut, or cattle management systems. There is a need to develop management techniques specifically tailored for the integrated peanut–cotton livestock-based production systems. It is unknown whether there is a need to develop different fertilization rates which take into consideration nutrient recovery with perennial grasses. Should new cotton and peanut varieties be developed for the sod-based systems? Furthermore, the sod-based system could be integrated with more modern techniques such as precision agriculture. However, this system holds great promise for both the sustainability and profitability for many years into the future.

	ACKNOWLEDGMENTS

 
This study was supported in part by Peanut Checkoff, USDA Special Projects, and Florida Northwest Water Management District.