Location: Soil Dynamics Research2013 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:
This is the final report for a two year bridge project 6420-12610-004-00D designed to keep us on sequence with other NP 216 projects. The final report for the original project was previously submitted, but the objectives and milestones completed under the life of bridge project will be summarized here. Substantial progress has been made in relation to conservation systems that include cover crops. New equipment designs related to cover crop management have generated renewed interest in the adoption of conservation systems, particularly for small vegetable farmers as evidenced by increased attendance at field days for small producers. Combining rolling operations with reduced herbicide use resulted in 80% of the herbicide saved that directly translates into monetary and environmental benefits for growers. Alternative control strategies that include cover crops and residual herbicides are being widely promoted by the Natural Resource Conservation Service (NRCS) and cooperative extension systems across the southeast to help control resistant weeds without the need for intensive tillage, which is a detriment to soil quality. Traditional production agriculture research related to conservation systems has also continued. Examining Nitrogen (N) requirements for winter wheat across fall tillage systems showed that N applied early in the spring across tillage systems is recommended and this information has been a popular topic for field days and other grower meetings across the state. Research efforts to examine the N contribution of a recently released sunn hemp cultivar for wheat are currently underway. Research examining N requirements and nutrient uptake and removal for forage sorghums used as a bioenergy source are near completion. Multiple sampling efforts to monitor changes in soil carbon levels have been completed with on-going laboratory analysis near completion. Technology transfer activities have continued, which have focused primarily on how to manage conservation systems to maximize the benefits. Typically, these activities are multi-disciplinary in order to highlight these benefits. New research has also been initiated that is designed to make economic comparisons for conservation systems and demonstrate to growers various scenarios to illustrate potential profitability and risk. Economic comparisons across these systems must continually be weighed against environmental concerns to ensure producers and natural resources remain viable well into the future. This type of information is being incorporated into the development of a dynamic programming model designed to identify the optimal crop rotation, while maximizing profits from cotton production. Once the model is complete, it can be easily adapted to scenarios applicable to other crops and will be a useful tool to demonstrate how conservation practices affect growers’ bottom line.
1. Conservation agriculture cotton out-performs conventionally tilled cotton. Weed control in conservation tillage is currently under threat due to herbicide resistant pigweed and other troublesome weeds. Winter cover crops are an important resistant management tool. Diversifying resistant management is increasingly being advocated by some in cooperative extension. Thus, a field experiment was conducted by an ARS scientist at the National Soil Dynamics Laboratory in Auburn, Alabama, evaluating weed control provided by integrating a high residue rye cover crop and varying herbicide intensity and preemergence herbicide placement in a glyphosate resistant cotton system. Pigweed densities in herbicide treatments that included a broadcast preemergence herbicide application were lower at three of five sampling dates compared to banding preemergence herbicide applications; however, the differences were not significant during the late season and cotton yields were not affected by preemergence herbicide placement. High-residue conservation tillage yields were 577 to 899 kg ha-1 more than conventional tillage, except at one site-year when conventional tillage treatment yields were higher. Conservation agriculture utilizing high-residue cover crops increased net returns over conventional tillage by $100 ha-1 or more 2 out of 3 years at both locations. High-residue cover crop integration into a conservation agriculture system reduced pigweed density and increased yield over winter fallow systems and the inclusion of a broadcast preemergence herbicide application can increase early-season pigweed control. Results from this study will increase weed control while reducing reliance on tillage to manage hard to control weeds.
2. Equipment transition from conventional to a conservation system. Producers transitioning to conservation systems want to avoid unnecessary financial risks and are reluctant to spend money on equipment they perceive as unnecessary, such as cover crop roller/crimpers and specialized planters. These producers feel they could utilize their existing tillage equipment. ARS scientists located at the National Soil Dynamics Laboratory in Auburn, AL, conducted a three-year field experiment to simulate a transition process from conventional to a conservation system for cotton. Results have shown that attaching row cleaners (either on subsoiler or planter) produced equivalent yields regardless of the surface disturbance zone associated with the subsoiler. As a result, row cleaners are recommended for at least one of the two implements. Farmers that own a wide subsoiler type (more surface soil disturbance) with row cleaners and traditional planters can utilize these implements in the transition period without the need to purchase a cover crop roller and narrow subsoiler (less surface soil disturbance). In high residue, it is not recommended to remove row cleaners from the subsoiler and planter (especially if rye was not rolled) as this practice produced the lowest cotton yields. These findings are important for producers interested in transitioning to conservation systems, but do not have the roller and the narrow type of subsoiler.
3. Conservation tillage cotton utilizing rye or clover suppresses Palmer amaranth. Weed control in conservation tillage is currently under threat due to herbicide resistant pigweed and other troublesome weeds. Winter cover crops are an important resistant management tool; however tillage is being advocated by some cooperative extension. Thus, a field experiment was conducted by an ARS scientist at the National Soil Dynamics Laboratory in Auburn, Alabama, evaluating integrating high residue cover crops weed control compared to conventional tillage followed by various secondary tillage methods in a glufosinate resistant cotton system. Results indicate a cereal rye or crimson clover cover crop can effectively reduce early season Palmer amaranth emergence in both inversion and conservation agriculture systems. For effective and season-long control of Palmer amaranth, one or more postemergence applications of glufosinate herbicide tank mixed with a residual preemergence herbicide will be needed in a glufosinate-based cotton production system to provide adequate weed control and maximize cotton yields. Results from this study will increase weed control while reducing reliance on tillage to manage hard to control weeds.
4. Inversion tillage is not a silver bullet to manage pigweed. Weed control in conservation tillage is currently under threat due to herbicide resistant pigweed and other troublesome weeds. Inversion tillage is being advocated by some cooperative extension. Thus, a field experiment was conducted by an ARS scientist at the National Soil Dynamics Laboratory in Auburn, Alabama, in collaboration with researchers at Auburn University evaluating weed control provided by preemergence and postemergence herbicides following inversion tillage or conservation tillage systems. Results indicate that a one-time tillage operation followed by a return to conservation tillage may aid in the reduction of Amaranthus density when used with preemergence applied herbicides. However, this system will likely not provide adequate control when high population densities of glyphosate resistance Amaranthus is present thus highlighting the need for a highly efficacious postemergence herbicide system. Thus, cropping systems that integrate other cultural practices such as high-residue cover crops, crop rotation, and alternative herbicide systems should be utilized to improve herbicide resistant weed control compared to high intensity tillage systems. Results from this study will increase weed control while reducing reliance on tillage to manage hard to control weeds.Tapley, M., Ortiz, B.V., Van Santen, E., Balkcom, K.S., Mask, P., Weaver, D.B. 2013. Location, seeding date, and variety interactions on winter wheat yield in Southeastern United States. Agronomy Journal. 105:509-518.