Location: Southeast Watershed Research2018 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.
The rye cover crop was successfully grown (10/2017-5/2018) and accompanying soil and plant sampling performed. Previously, summer crops were planted in chemically killed and rolled cover crops. In this reporting period, the cover crop was hayed since the plots are being decommissioned and a new set of research plots being established starting in June 2018. Continued on the 30 small plots at Gibbs Farm under Phase II (2017, 2018, and 2019) to assess the impacts of application of flue gas desulfurization gypsum and poultry litter on corn production, soil properties, and nutrients in runoff. In Phase II, poultry litter and gypsum rates are set at 2 tons per acre per year compared with 6 tons per acre per year during Phase I (2014, 2015, and 2016) 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. A winter rye cover was successfully grown and biomass determined. The rye was rolled and chemically killed before incorporating into the soil by disking and planting of the 2018 summer corn crop which is expected to be harvested in September 2018. Leaf area index will be measured 5 times similar to that during the summer 2017 corn. Soil and rye biomass samples were obtained. Surface runoff samples were obtained from small in-field runoff collectors. Microbial biomass C and N were assessed from 3-ft soil cores taken in early spring 2017 from each of the 30 plots and 16 buffer areas and sectioned off into 6 inch lengths representing changes during the higher application rate period. The research is partially funded through a Trust Fund Cooperative Agreement with Southern Company Inc. and Duke Energy. Planting of open-pollinated pearl millet and pigeon peas was completed in April, 2018 in preparation of seed sources. Seed will be cleaned and stored this fall for use in the fiscal year 19 (FY19) summer growing season. A peanut and cotton summer crop was successfully grown (2016 and 2017, respectively), as were rye cover crops (2016/2017 and 2017/2018). 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. 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.
1. No identifiable environmental risks were observed in a three year study where flue gas desulfurization gypsum (FGDG) produced with current (new) technology was used as an amendment on a Piedmont clay soil treated with or without broiler litter. 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 at 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 at Tifton, Georgia, found 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.
Liebig, M.A., Herrick, J.E., Archer, D.W., Dobrowolski, J., Duiker, S.W., Franzluebbers, A.J., Hendrickson, J.R., Mitchell, R., Mohamed, A., Russell, J., Strickland, T.C. 2017. Aligning land use with land potential: The role of integrated agriculture. Agricultural and Environmental Letters. 2:170007.
Xavier, S., Olson, D.M., Coffin, A.W., Strickland, T.C., Schmidt, J. 2017. Perennial grass and native wildflowers: a synergistic approach to habitat management. Insects. 8(4):104-117. https://doi.org/10.3390/insects8040104.
Saha, U., Endale, D.M., Tillman, P.G., Johnson, W.C., Gaskin, J., Sonon, L., Schomberg, H.H., Yang, Y. 2017. Analysis of various quality attributes of sunflower and soybean plants by near infra-red reflectance spectroscopy: Development and validation of calibration models. American Journal of Analytical Chemistry. 8:462-492. Https://doi.org/10.4236/ajac.2017.87035.
Schomberg, H.H., Endale, D.M., Jenkins, M., Chaney, R.L., Franklin, D.H. 2018. Metals in soil and runoff from a piedmont hayfield amended with broiler litter and flue gas desulfurization gypsum. Journal of Environmental Quality. 47:326-335. https://doi.org/10.2134/jeq2017.09.0353.
Tillman, P.G., Gaskin, J., Endale, D.M., Johnson, W.C., Schomberg, H.H. 2016. Parasitism of Megacopta cribraria (Hemiptera: Plataspidae)by Paratelenomus saccharalis (Hymenoptera: Platygastridae) in organic soybean plots in Georgia, USA. Florida Entomologist. 99(2):300-302.
Delgado, J.A., Weyers, S.L., Dell, C.J., Harmel, R.D., Kleinman, P.J., Sistani, K.R., Leytem, A.B., Huggins, D.R., Strickland, T.C., Kitchen, N.R., Meisinger, J.J., Del Grosso, S.J., Johnson, J.M., Balkcom, K.S., Finley, J.W., Fukagawa, N.K., Powell, J.M., Van Pelt, R.S. 2016. USDA Agricultural Research Service creates Nutrient Uptake and Outcome Network (NUOnet) Journal of Soil and Water Conservation. 71(6):147A-148A. https://doi.org/10.2489/jswc.71.6.147A.
Spiegal, S.A., Bestelmeyer, B.T., Archer, D.W., Augustine, D.J., Boughton, E., Boughton, R., Clark, P., Derner, J.D., Duncan, E.W., Cavigelli, M.A., Hapeman, C.J., Harmel, R.D., Heilman, P., Holly, M.A., Huggins, D.R., King, K.W., Kleinman, P.J., Liebig, M.A., Locke, M.A., McCarty, G.W., Millar, N., Mirsky, S.B., Moorman, T.B., Pierson, F.B., Rigby, J.R., Robertson, G., Steiner, J.L., Strickland, T.C., Swain, H., Wienhold, B.J., Wulfhorts, J., Yost, M., Walthall, C.L. 2018. Evaluating strategies for sustainable intensification of U.S. agriculture through the Long-Term Agroecosystem Research network. Environmental Research Letters. 13(3):034031. https://doi.org/10.1088/1748-9326/aaa779.
Pisani, O., Strickland, T.C., Hubbard, R., Bosch, D.D., Coffin, A.W., Endale, D.M., Potter, T.L. 2017. Soil nitrogen dynamics and leaching under conservation tillage in the Atlantic Coastal Plain, Georgia, USA. Journal of Soil and Water Conservation. 72(5):519-529. https://doi.org/10.2489/jswc.72.5.519.