Location: Southeast Watershed Research2012 Annual Report
1a. Objectives (from AD-416):
1. Determine the effects of legume cover crops and soil amendments (e.g., poultry litter and flue gas desulfurization gypsum) on nutrient cycling and other soil processes in cropping systems. 1.1. Quantify the impact of gypsum application on infiltration, runoff, bulk density, soil loss, and soil-water partitioning within the rooting zone on a Tifton soil in a sweet sorghum-peanut-cotton rotation. 1.2. Quantify the impact of gypsum on rooting depth and estimated plant available water in a Tifton soil in a sweet sorghum-peanut-cotton rotation. 1.3. Determine the effect of gypsum on above and below-ground winter cover crop biomass production and associated effects on soil carbon sequestration, summer crop biomass, yield index, and nitrogen use efficiency. 2. Characterize the effects of cropping system, soil management and residue removal rate on soil carbon, specifically how changes in soil carbon storage impact nitrogen use, soil water storage and crop water use, and soil erosion and carbon loss associated with extreme rainfall events. 3. Determine the effects of cropping system, soil management and residue removal rate on the levels and seasonality of trace gas (CO2, CH4, and N2O) emissions. 4. Assess the dissipation, fate, and transport of herbicides and fungicides in soil as a function of soil management and residue removal rate. 4.1. Evaluate pesticide soil persistence including metabolite accumulation and decay as influenced by soil properties, tillage, agronomic amendments, pesticide formulation, and pesticide mode and frequency of application. 4.2. Determine edge-of-field pesticide and degradates loads at the field scale as a function of crop type, gypsum application, and pesticide properties during cotton-sweet sorghum-peanut production with strip- and no-till management.
1b. Approach (from AD-416):
This project will evaluate soil processes in cropping systems that incorporate biomass crops into traditional annual row crop rotations and that facilitate the conversion of idle and marginal agricultural lands to perennial biomass production systems. Goals will be accomplished through provision of: improved data (C&N accretion and cycling rates, water availability and quality effects, evapotranspiration estimates, yield potential and yield indices) for crop production and watershed model calibration; site-specific C and N cycling and trace gas data for the ARS GRACENet database and the Southern Multistate Research Committee’s project S1048; soil quality and hydraulic data that will aid in the development of conservation practice targeting recommendations for sensitive landscape positions within farms and improve hillslope, small watershed, and riparian model parameterizations for Little River Experimental Watershed (LREW); improved understanding of the relationships between crop water use efficiency, soil characteristics (texture, bulk density, carbon content, soil-water holding capacities), and crop biomass production that will facilitate validation of soil water estimation by satellite; and improved information on the effects of conservation practice, future land use, and environmental change scenarios for the southeastern coastal plain region to integrated National Program Assessments’ “what-if” analyses. Emphasis is placed on studies that: 1) define benefits of combining gypsum with conservation-tillage in row crop production systems; 2) use leguminous cover crops to improve the net energy balance of production systems that include biofuels feedstocks; 3) develop guidelines for appropriate nutrient (poultry manure and inorganic fertilizer nitrogen, phosphorus, and potassium) and water amendment rates for perennial grass feedstock production systems; and 4) determine how agronomic and soil management practices impact the fate and soil persistence of herbicides used for control of glyphosate resistant weeds rapidly spreading through Southeastern landscapes.
3. Progress Report:
During this first year of the project, we have conducted baseline soil characterizations and established the first crop "Blade" biomass sorghum at the University of Georgia Gibbs Farm (Objective 1). All plots were planted to biomass sorghum in May. The cooperator responsible for mini-rhizotron measurements resigned in February. Root biomass and depth measurements will now be made only annually through soil core collection. Coring will be conducted post-harvest for the biomass sorghum. Nitrogen fertilization rates at the Ponder Farm napier grass biofuels study were increased from 84 to 168 kg N ha-1 (Objective 2). Soil water content continues to be sampled weekly. Soil C and N sampling continues, and root biomass will be measured in 2013. Crop biomass production and C&N content are quantified annually. Fertilizer application at the Shellman napier grass production farm were conducted as scheduled and irrigation regimes have been implemented. Soil cores were collected in April for determination of soil water holding capacity. Sample analysis is proceeding on schedule. Winter cover harvests and cotton and biomass sorghum plantings were conducted as scheduled at the Sanders-Belflower Farm. Soil fertility samples will be collected on schedule at 45 days after planting. Bases for chambers have been installed at the Ponder Farm and Shellman sites, tested for leaks, and scheduled sampling began in Spring, 2012(objective 3). Sampling frequency has been increased to bi-weekly primarily to account for variations in soil moisture and to have a more robust data set to calculate annual rates. Soil sampling for determination of pesticide degradation rate will be conducted (Objective 4). Composite surface soil samples (0 to 2 cm depth) were collected from the plot at the top of the slope (plot 7) from both the no-till and conventional-till areas after the field had been prepared for planting and prior to herbicide application. The soil samples were sieved (2 mm), 50-g subsamples placed in incubation bottles, the water content adjusted field capacity, and fortified with atrazine coated on fine sand at the label rate. Bottles were maintained in a laboratory incubator at 25oC with 3 samples remove for analysis on 0,3,7,14,28,42,63, and 100 days after the atrazine treatment. Samples are being analyzed for atrazine and principal soil degradates. Results will be compared to an incubation study conducted in the same way in 2011. This work coincided with the first use of atrazine on these plots in at least 10 years. Findings will help determine if accelerated atrazine degradation conditions will develop following use of this product for weed control.
Strickland, T.C., Potter, T.L., Truman, C.C., Franklin, D.H., Bosch, D.D., Hawkins, G.L. 2012. Results of rainfall simulation to estimate sediment-bound carbon and nitrogen loss from an Atlantic Coastal Plain (USDA) ultisol. Soil and Tillage Research. 122:12-21.