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ARS Home » Southeast Area » Tifton, Georgia » Southeast Watershed Research » Research » Research Project #430954

Research Project: Quantification and Improvement of the Efficiency of Inputs and Management Practices of Southeastern Agriculture to Better Meet Yield, Environmental and Economic Goals

Location: Southeast Watershed Research

2019 Annual Report

Objective 1: Quantify reduced soil loss, nutrient, water, and pesticide use efficiencies of best management and conservation practices and devise options for improvements suitable for southeastern cropping systems. Objective 2: Quantify the effects of integrating bioenergy feedstocks into southeastern cropping systems on soil resources and environmental quality and develop options for mitigating adverse effects. Objective 3: Quantify potential benefits and risks of using flue gas desulfurized gypsum with and without broiler litter in southeastern cropping systems to reduce phosphorus loss via runoff.

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.

Progress Report
This is the final report for bridging project 6048-11130-004-00D which terminated in November 2018 and has been replaced by new project 6048-111300-005-00D, "Integrating Animal and Industrial Enterprise Byproducts in Gulf Atlantic Coastal Plain Cropping Systems for Enhancing Productivity, Efficiency, and Resiliency of Agroecosystems." For additional information see new project. A peanut and cotton summer crop was successfully grown, as were rye cover crops. Appropriate soil and biomass sampling was performed. Hydrologic monitoring continued until the end of 2017. In early January 2018, hydrologic sensors and recorders started being pulled out as part of the decommissioning of these research plots, which originally were established in 1999, and the establishment of new research plots in line with the newly approved and Long Term Agroecosystem Research (LTAR). Therefore, the last summer crop on these research plots was in 2017. Approval was sought and obtained for the removal of Objective 2 as the final bioenergy feedstock crop in the rotation of the previous research plan was collected in 2015. Three summer corn (2016, 2017, 2018) and two winter rye cover (2016/2017 and 2017/2018) crops were successfully grown and corn grain yield and rye biomass determined. Beginning in April 2017, rates for broiler litter and gypsum were reduced from the previous (2014, 2015, 2016) 6 tons per acre per year to 2 tons per acre per year because 1) these are typical rates producers would apply in fields, and 2) we want to evaluate the changes in the assessed variables at high and typical application rates. Leaf area index was measured 5 times through the growth stages of corn in 2017 and 2018. Soil samples and rye biomass samples were collected. Extractible and total metal analysis for soil samples was carried out at the University of Georgia. Carbon and nitrogen analysis for rye biomass samples was carried out in-house. Approval was sought and obtained for the removal of collection of yearly rooting depth data using soil cores as the 30 plots are small (10 ft by 18 ft) and the yearly collection of such cores from each plot to follow rooting depth was considered excessive and potentially destructive compromising the integrity of the overall study. Indirect methods (yield, water use efficiency, etc.) will be used to assess rooting depth differences. However, in early spring 2017, soil cores were taken to 3-ft depth from each of the 30 plots and 16 buffer areas and sectioned off into 6 inch lengths to assess soil physical, chemical, and biological changes during the high rate of application period. Analyses for microbial biomass carbon and nitrogen have been completed. Runoff samples were collected and processed (filtered and non-filtered) and sent to the University of Florida for nitrate, ammonium, total nitrogen, ortho-phosphate, and total phosphorus determination. Analyses have been completed and the data archived. Analysis for metals in runoff will be carried out in-house. Six peer-reviewed journal articles have been published.

1. Flue gas desulfurization gypsum (FGDG) produced with current (new) technology. Flue gas desulfurization gypsum is a by-product from electric generation plants created when removing sulfur from burning coal. Large quantities are available in many areas of the U.S. Heavy metals were once found in coal combustion by-products but new technology has reduced their potential to contaminate FGDG. Broiler litter from chicken growing facilities contains plant available nitrogen, phosphorus, and potassium that can be used as fertilizer. Additions to poultry diets of compounds to improve bird health have resulted in broiler litter having unwanted elements like arsenic (As), copper (Cu), and zinc (Zn). FGDG provides calcium which can reduce runoff losses of phosphorus and could reduce runoff losses of other elements. ARS researchers in Tifton, Georgia, evaluated, using simulated rainfall, the potential for FGDG to reduce loss of As, Cu, Zn, cadmium (Cd), Chromium (Cr), mercury (Hg), and lead (PB) when applied with or without broiler litter on a Coastal bermudagrass (Cynodon dactylon L.) hayfield. Runoff concentrations of As were 6 times greater where plots received broiler litter. Additions of FGDG did not reduce As losses. However, after three years of applications of FGDG and broiler litter, soil concentrations of As, Hg, and Cr were well below levels of environmental concern. Although FGDG did not reduce runoff losses of As from broiler litter, it also did not cause any identifiable environmental risks.

2. Finding the right balance between N supply and crop demand is key to optimize yield, profit, and environmental protection. ARS researchers in Tifton, Georgia discovered that strip tillage (ST) in conjunction with winter cover crops and poultry litter application improved plant nitrogen availability by more than 24 lb/acre/yr in sandy landscapes of the southeastern Coastal Plain via microbial cycling of organic N and reduction of nitrate leaching. Total soil N content increased 27% over five years with ST compared to 22% with conventional tillage (CT). Cumulative nitrate-N leached from soils during the five-year study was 126 lbs/acre (CT) versus 109 lbs/acre (ST). Both of these values were higher than the five year average tile flow N losses of 99 versus 88 lbs/acre, but suggest that leaching from the top 6 in of soil is an important pathway for dissolved N loss from the rooting zone in this landscape. Regardless of tillage, soil microbial biomass N was equal to or higher than soil inorganic N, suggesting that soil microbial biomass is a key factor for retaining N in the rooting zone and thus mitigating soil nitrate loss and delivery to ground and surface waters.

3. Long-term studies essential for characterizing risk from extreme events. ARS researchers in Tifton, Georgia, demonstrated how proper grazing management (i.e., maintaining good grass cover, including rotational grazing, and limiting fertilizer application) can provide valuable ecosystem services, including reduced soil erosion and pollutant flux to nearby waterways. The 11-year study (1999-2009) also demonstrated the critical need to conduct natural resources research over the long-term so that data capturing cyclical events such as exceedingly wet or dry years, and more importantly when land management activities coincide with the timing of such extreme events. For example, surface transport processes were the dominant drivers of pollutant fluxes and highlighted the importance of managing grazing to maintain adequate forage cover on pastures. The concurrence of cattle with hydrologic events that favor transport processes (high rainfall, runoff, peak flow, etc.) resulted in six events (probability of exceedance <15%) that accounted for 53% of the total phosphorus loss over the 11-year study while drought periods had low hydrologic transport and phosphorous losses. The study provided data that can be used to calibrate, test, and validate water quality models simulating the ecosystem services effects from producer operations typical of grazed areas of the southeastern U.S., and the incorporation of extreme weather events in such simulations can assist in the development of risk mitigation strategies.