Conservation Tillage Systems in the Southeast

Benefits of Conservation Tillage Systems

Overview

There are both environmental and economic benefits to conservation tillage systems. Environmental benefits include improved water quality; reduced nutrient losses; increased water availability; improved air quality; and improved soil quality, meaning increased organic matter and improved soil structure, porosity and tilth. Economic and societal benefits include improved quality of life (reduced labor, greater flexibility in planting); improved profitability (reduces wear and tear on equipment, saves fuel and fertilizer, improved productivity, carbon credits); and improved wildlife habitat. The benefits are many, diverse and interwoven. More detail is provided on the benefits of conservation tillage in the sections below.

Environmental Benefits

Reduced Soil Erosion

When soil is tilled and loosened, and residue is buried or removed, the potential for erosion increases. The Southeast has highly erodible soils and experienced irreversible soil erosion prior to 1900 [31, 48]. Research has proven that conservation tillage, including crop-residue management, conserves soil and water on southeastern soils [31, 50] and improves soil productivity. On the loess silty-clay loams of northern Mississippi, soil losses declined about 86 percent when no-till equipment with fluted coulters was used rather than conventional tillage [37]. In the Southern Coastal Plain on highly weathered loamy sands planted in cotton, sediment losses were reduced significantly using conservation tillage rather than conventional tillage [52]. In the Southern Piedmont sandy-clay loams and sandy clays, conservation tillage has been shown to reduce erosion [30] when compared to conventional tillage. With the inclusion of winter cover crops, it will also restore soil productivity [31].

Improved Soil Health

In the humid Southeast, conservation tillage systems have positive effects on chemical, physical and biological soil properties when compared to conventional tillage. Reduced mechanical disturbance results in less destruction of soil organisms and their habitat. Biological activity is more robust. Organic matter in the soil and at the soil surface provides nourishment for soil organisms that are part of the foundation of the food web. Soils in conservation tillage systems generally have a greater abundance of earthworms, arthropods, microorganisms, fungi and bacteria. Disease is reduced due to the greater competition between disease microorganisms and beneficial microorganisms. Plants grown under conservation tillage experience less stress and are likely to be stronger and more resistant to disease.

Researchers have found higher values of organic matter, nitrogen, phosphorus, potassium, calcium and magnesium in cropping systems that utilize conservation tillage systems rather than conventional tillage systems. Results in Georgia have shown that the degree to which soil organic matter accumulates depends on the amount of organic carbon returned to the soil [27]. This suggests that the addition of cover crops in winter and limiting residue removal will increase organic-matter levels. Higher organic-matter levels have been shown to increase the soil’s cation-exchange capacity, which helps keep nutrients in place and in a form easily exchangeable with plant roots.

Plant roots in conservation tillage systems have been shown to be more abundant and extensive, both laterally and vertically, than roots in conventional tillage systems. These extensive root networks provide more moisture and nutrients for plant growth. Edwards et al. [20] found that conservation tillage increased soil organic matter 56 percent in the Southeast, while no change in organic matter was measured for conventional tillage.

Improved Water Conservation

Crop residue protects soil from raindrop impact, which in turn reduces soil crusting that results in surface sealing [42]. Soil crusting reduces water infiltration and air exchange that can impair crop germination. In a rainfall simulation study on a Southeast silt loam, researchers found that runoff losses averaged 28.7 mm for conventional tillage and 16.7 mm for conservation tillage [44]. In Alabama, on Southern Coastal Plain loamy sand, researchers found that conservation tillage produced only half as much runoff as conventional tillage plots [47, 51, 52]. Conservation tillage systems increase soil porosity, resulting in increased rainfall infiltration and soil water-storage capacity [8, 21].

Improved Air Quality

In many regions, erosion by wind can be a serious problem both environmentally and agronomically. In the east, the Southern Coastal Plain soils are most vulnerable to wind erosion. Wind erosion factors influenced by soil management and sediment supply (or how loose and easily transportable the soil is) include vegetative cover and timing of farming operations. Conservation tillage does not loosen or invert the soil; it leaves vegetation in place to help prevent wind-erosion losses. Crop residues on the soil surface reduce wind velocity and the ability of wind to move soil particles.

Improved Wildlife Habitat

Management of agricultural land has vital implications for wildlife. Just as humans require nutritious food, clean water and adequate shelter (refuge from the environment and from predators), so does wildlife. Sedimentation is a critical water-quality problem, especially for aquatic fauna and other wildlife that feed directly on them. Conservation tillage systems reduce sedimentation in water bodies by reducing soil erosion.

Conservation tillage also provides food opportunities and shelter for small mammals and birds [3] such as mice, rabbits, bobwhite or quail. This in turn provides nourishment for predators such as rattlesnakes, raccoons, great horned owls, red-tailed hawks, bobcats and coyotes. Researchers have reported higher nest densities and nest success in conservation tillage fields as compared to conventional tillage fields [14, 18, 34]. In the Southeast, cotton fields are abundant and provide little to no cover or food source if clean tilled. Cederbaum [10] reported higher densities of breeding birds in conservation-tillage cotton fields as compared to conventional tillage, especially with conservation tillage fields using strip cropping. Wildlife specialists recommend that areas within and around conservation tillage fields be managed to provide habitat, especially for birds and rabbits.

Economic Benefits

When farms convert from conventional tillage systems to conservation tillage systems, there is potential to lower production costs and improve farm profitability. The agronomic benefits associated with conservation tillage practices, such as improved soil productivity, may improve yields, thereby increasing net returns [6, 33]. While this potential exists, profitability of the cropping enterprise depends on a number of additional factors, including effective management, soil suitability, pest pressures and climate.

Lower Production Costs

Cost savings with conservation tillage systems over conventional systems primarily stem from reductions in the use of labor and machinery. This includes both short- and long-term cost savings in variable and fixed labor costs as well as fuel and machinery costs. The savings will likely differ from farm to farm due to differences in weather and farm characteristics, such as farm size, as well as management approaches [54]. Labor savings are a result of a decrease in pre-harvest activities. This includes reductions in operator labor for machinery as well as reductions in hand labor for other farming activities such as maintenance of equipment.

Reductions in fuel and machinery costs result from fewer passes over the field with less tillage and cultivation. Fewer pieces of equipment are needed, and smaller, less powerful tractors can do the work. A significant savings results from a decrease in diesel-fuel consumption. This savings increases as diesel-fuel prices go up. Labor savings and longer machinery life will allow farmers to increase the acres of land being farmed, further increasing farm profits and viability. Another factor that will lower production costs is the inclusion of high-residue winter cover crops. Winter cover crops reduce weed pressure and improve water conservation, resulting in reduced pesticide and irrigation costs [45].

Improved Crop Yields and Revenue Opportunities

Studies comparing conventional and conservation tillage systems have mixed results when analyzing crop yields. In a number of cases, conservation tillage systems resulted in reduced yields during transition to conservation tillage, but compensated with cost savings [46]. In a Georgia Piedmont Ultisol, conservation-tillage cotton fertilized with broiler litter produced more lint in four out of five years, compared to conventional-tillage cotton fertilized with mineral fertilizer [22, 23]. Averaged over the five years, conservation tillage, regardless of fertilizer, produced 32 percent more cotton lint than conventional tillage.

Addition of cover crops to conservation tillage systems often results in increased crop yield and net returns compared to conservation systems without cover crops. Past agronomic research has shown the potential yield benefits of using cover crops prior to cash crop planting [24, 35, 40]. For example, Bergtold et al. [6] examined the profitability of alternative mixtures of high-residue cover crops in conservation tillage systems. They found that net returns for cotton with a rye/black oat cover crop mixture increased 10–37 percent over the conventional tillage treatment.

Financial Incentives

To further enhance the profitability of conservation tillage systems, especially during initial periods of adoption, take advantage of financial incentives from programs such as EQIP and Conservation Stewardship Program (CSP) offered by the Natural Resource Conservation Service (NRCS). Other potential sources of revenue in conservation tillage systems may come from activities such as winter annual grazing [1], providing farm operations with additional sources of income and helping to reduce risk.

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