Location: Soil Dynamics Research2012 Annual Report
1a. Objectives (from AD-416):
Develop conservation tillage systems technologies for Southeastern soils (Coastal Plain, Tennessee Valley, Piedmont, and Blackbelt) that improve soil quality, increase plant available water, improve profitability, and conserve natural resources. Specific objectives include: (1) develop cover crop management technologies that enhance soil protection from rainfall events, increase soil organic matter accumulation, and suppress weeds; (2) develop and evaluate row crop production technologies that enhance sustainability, productivity, and environmental quality of degraded soils and increase plant available water; and (3) integrate new components and technologies into conservation management systems that reduce soil erosion, drought stress, and risk associated with production agriculture.
1b. Approach (from AD-416):
Coordinated plot and field-scale studies will be implemented to develop strategies for managing soils to reduce economic risks of short-term drought and increase farm profitability, improve soil quality, and enhance carbon storage. Problems include: (1) increasing crop rooting depth; (2) improving soil properties associated with infiltration and water retention; (3) developing decision aides for improved soil and water management and increased profitability; (4) developing integrated weed management strategies through improved understanding of interactions between cover crop residue and weed biology/ecology; (5) developing design principles for improved implements that facilitate management of cover crops, soil compaction, and high-residue conservation cropping systems; and (6) assess and predict economic viability of conservation practices.
3. Progress Report:
Substantial progress has been made in relation to conservation systems that include cover crops. A walk behind roller/crimper was developed for managing cover crops in small vegetable farms/gardens that uses a limited power source such as garden tractors. This innovation allows small farmers to take advantage of the benefits associated with cover crops that have been demonstrated for traditional row crop farmers across large scale acreages. Other studies have examined different management aspects of cover crops related to termination methods (flail mowing and rolling), and combining roller/crimper operations with planting operations to minimize trips across the field that will reduce expenses. In addition, custom designed row cleaners/residue managers are being evaluated to also assist with high residue cover crop management. Other research efforts have focused on how different agricultural practices affect soil carbon sequestration, soil physical properties, and plant-water availability. Multiple sampling efforts were completed in several on-going projects that included collaborations with university researchers. Laboratory work to complete all sample analyses continues on the collected samples with a large portion of these efforts related to biomass harvest for bioenergy use, and are associated with the Renewable Energy Assessment Project (REAP), an ARS multi-location research project that involves 23 research units. One major focus of REAP is to develop a database system to compile all the data collected from various locations that may be accessed by different entities, such as computer modelers and other scientists. Scientists from the National Soil Dynamics Laboratory at Auburn, AL, were members of the REAP Data Management Team that was pursuing this effort. This research also includes an effort to determine if crop residues, including cover crops, could be partially or fully harvested for bioenergy purposes without degrading soil quality. Other crop production research in conservation systems has focused on the tropical legume, sunn hemp. On-going efforts are examining how planting dates affect biomass and nitrogen (N) production for a new sunn hemp cultivar capable of producing seed in Alabama. The subsequent N production from this legume will be examined as a source of N for winter wheat production. Additional research has examined N requirements for winter wheat across fall tillage systems. These findings show that N applied early in the spring across tillage systems is recommended and have been popular topics for field days and other grower meetings across the state.
1. Powered rolling and crimping device for cover crop termination. In small vegetable/organic systems, bigger tractors are not used, because they are too expensive, heavy, and large for small planting areas. Instead, 2-wheel walk-behind tractors and small implements are widely utilized, but there were no small rollers/crimpers available to effectively crimp and terminate cover crops without herbicides (as required in organic systems). Because of this problem, there was a need to develop an effective, low weight roller/crimper compatible with 2-wheel tractors. An ARS scientist from the National Soil Dynamics Laboratory in Auburn, AL, conceived a unique powered roller/crimper for self-propelled walk-behind tractors that allows growers with small farms to successfully terminate and manage cover crops without commercial herbicides. For his invention, U.S. Patent No.: US 8,176,991 B1 was issued on May 15, 2012. The development of this patented powered roller/crimper is important for small no-till organic vegetable systems, where commercial herbicides are banned, and traditional rollers are too heavy for limited power 2-wheel tractors and too large for narrow beds typical of smaller farms in the USA and worldwide.
2. Sunn hemp as a nitrogen (N) source for winter cover crops. Sunn hemp is a tropical legume that produces plant biomass and nitrogen quickly, but seed is very hard to obtain and expensive, if available. Scientists with USDA-ARS located at the National Soil Dynamics Laboratory in Auburn, AL, in cooperation with Auburn University examined the agronomic performance of a new sunn hemp cultivar, across different planting dates and seeding rates, breed to produce seed in the Southeast and determine how much N is available to a subsequent rye winter cover crop following corn and wheat harvests. Sunn hemp biomass production was inconsistent but did relate to the growing season. Neither planting date nor seeding rate affected rye biomass production, but rye biomass averaged over both planting dates following wheat/sunn hemp averaged 43% and 33% greater than rye following fallow. Rye biomass following corn/sunn hemp was equivalent to fallow plots, which was related to the shorter growing season. This research indicates early planting dates are recommended for sunn hemp with seeding rates between 17 and 34 kg/ha to maximize biomass and subsequent N production as a N source for winter cover crops in the Southeast.
3. Weed control for conservation tillage. Weed control in conservation tillage is currently under attack due to troublesome herbicide resistant weeds. Rotating herbicide modes of action is an important resistant management tool. Unfortunately, lack of alternative herbicide modes of action included in glyphosate resistant cotton herbicide systems continues. Thus, a field experiment was conducted by USDA-ARS scientists at the National Soil Dynamics Laboratory in Auburn, AL in cooperation with Auburn University to evaluate integrating high residue cover crops, alternative row spacings, and conventional, glyphosate and glufosinate cotton systems. The glufosinate and glyphosate weed management systems controlled at least 97% of large crabgrass, Palmer amaranth, sicklepod, and smallflower morningglory, while the conventional system controlled 89, 73, and 87 to 98% of large crabgrass, smallflower morningglory, and Palmer amaranth, respectively. In this study, the glyphosate weed management system resulted in higher cotton yield than the conventional and glufosinate systems. Cotton yield response to tillage system varied among years, with conservation tillage yielding more than conventional tillage during a dry year.
4. Harvest of winter cover crops for bioenergy. Winter cover crops can improve the productivity of many agricultural systems by protecting the soil from erosion and increasing soil organic matter contents, but emerging bioenergy markets for plant biomass feedstocks, like from a cover crop, could threaten agricultural productivity of systems that rely on the beneficial effects of cover crops. A study conducted by USDA-ARS scientists at the National Soil Dynamics Laboratory in Auburn, AL in cooperation with Auburn University examined the benefits of a winter cover crop for cotton production and revealed that including a cover crop, despite being harvested for bioenergy production, was more beneficial than not using a cover crop in the first place. This information can help increase cover crop adoption by demonstrating the benefits, as well as showing the potential of cover crops as another source of income to farmers through bioenergy feedstock production.
Price, A.J., Kelton, J.A., Mosjidis, J. 2012. Allelopathic weed suppression through the use of cover crops. In: Price, A.J., editor. Weed Control. Rijeka, Croatia: Intech Press. p. 115-130.