Location: Adaptive Cropping Systems Laboratory2017 Annual Report
Objective 1: Develop strategies using cover cropping and biosolids management to mitigate green-house gas (GHG) emissions and improve soil health. 1.A) Evaluate soil carbon (C) sequestration with cover crops to mitigate GHG emissions. 1.B) Evaluate the ability of biosolids management strategies to sequester C and thereby reduce GHG emissions. Objective 2: Develop strategies for managing fertilizer-N in cropping systems and manure NH3-N in high-residue tillage systems, to improve N-use efficiency and air quality. 2.A) Conduct field crop research with a corn-wheat-soybean rotation to evaluate 15N uptake efficiencies of genetically modified corn, conservation of N by cover crops, and soybean N2 fixation. 2.B) Evaluate and develop best management practices for reducing ammonia volatilization and to estimate ammonia losses from manures. Objective 3: Improve descriptions of biological mechanisms controlling bioactive P release to soils, and develop improved fate models and conservation practices to enhance P use efficiency. 3.A) Evaluate nutrient conservation practices based on enhanced understanding of rhizosphere microbiology and enzymology that regulate the release of bioactive manure-P and soil-P to crops and soil. 3.B) Evaluate relevance of current algorithms in use to include rhizosphere microbiology and enzymology processes when modeling P behavior and transport in APEX and similar models. Objective 4: Develop beneficial uses of agricultural, industrial, and municipal byproducts to enhance crop production and reduce risks to the environment from potential contaminants. 4.A) Conduct phytostabilization research using mixtures of organic resources with byproducts and alkaline amendments to achieve functional remediation and revegetation of barren and biologically dead metal contaminated soils. 4.B) Conduct phytoextraction/phytomining research to identify effective plant species and optimize the agronomic productivity of phytoextraction technologies. 4.C) Conduct research and risk evaluation to assess the risks and benefits from use of industrial, municipal and agricultural byproducts to improve crop production and reduce risk to the environment from byproduct constituents. 4.D) Investigate the use of mixtures of organic amendments, limestone byproducts, flue gas desulfurization gypsum and leachable alkalinity to correct subsoil acidity and improve soil fertility.
Obj. 1A. A replicated six-year field experiment will be completed to evaluate the rate and quantity of carbon sequestrated by winter cover-crops of rye, hairy vetch, and a rye plus hairy vetch mixture, as compared to a traditional no-cover condition. These data will assess and develop agricultural practices for mitigating global warming. Obj. 1B. Agricultural use of biosolids could improve soil carbon sequestration and thereby reduce greenhouse-gas emissions. Replicated field research will be conducted on plots previously treated with different rates and types of biosolids, to determine if biosolids can increase soil carbon sequestration. Obj. 2A. Labeled nitrogen fertilizer will be used in a corn-wheat-soybean rotation to evaluate nitrogen use efficiencies of genetically modified and non-modified corn, to measure conservation of corn residual fertilizer by winter-wheat, and to estimate nitrogen fixation of double-crop soybeans. Improving nitrogen use efficiency will reduce nitrogen losses to the environment while maintaining profitability. Obj. 2B. Ammonia volatilization is a major loss of plant-available nitrogen from surface applied manures. A series of wind tunnel field studies will be conducted to evaluate the ability of new high-residue tillage implements to conserve ammonia, but still maintain surface residues to control erosion. Obj. 3A. Laboratory incubation-fractionation studies will be conducted to mathematically describe phosphorus transformations and availability in manured soils. These results will assess the advantages and disadvantages of adding organic-phosphorus turnover to existing models. Obj. 3B. A critical evaluation of phosphorus transformation and transport modules within existing phosphorus models will be conducted by validation against long-term field and simulated rainfall studies. The evaluation will focus on the use of rhizosphere microbiology and enzymology for modeling phosphorus. Obj. 4A. Two field locations will be studied using various mixtures of industrial, municipal, and agricultural byproducts to remediate and revegetate barren and heavy-metal contaminated soils. The studies will monitor plant yield and composition to assess byproduct performance and possible risks to wildlife. Obj. 4B. Growth chamber and greenhouse research on phyto-mining will use various fertilizer nutrients and topsoil/subsoil combinations to identify plant species and management practices that optimize agronomic productivity and that extract nickel from nickel-rich soils. Obj. 4C. A two-year field study will be conducted in Appalachia comparing the uptake of nutrients and metals by peanut and wheat from additions of poultry litter, flue gas desulfurization gypsum, and mined gypsum. A risk assessment on the use of flue gas desulfurization gypsum and mined gypsum in U.S. soils will also be done. Obj. 4D. A greenhouse study will be conducted to evaluate mixtures of organic amendments, limestone byproducts, flue gas desulfurization gypsum, and leachable alkalinity to correct subsoil acidity for alfalfa. Subsoil acidity commonly limits rooting depth in soils across the mid-Atlantic and Southern regions of the U.S..
Objective 1A. The fourth year of a six-year field experiment was completed to evaluate the rate and quantity of carbon sequestrated by winter cover-crops of rye, hairy vetch, and a rye plus hairy vetch mixture, as compared to a traditional no-cover condition. The cover crop dry matter production, carbon content, and nitrogen content were measured, as well as the yield of the following corn crop. These data provide a fourth data point that documents the annual carbon and nitrogen additions to the soil-crop system from cover crops. These cumulative annual carbon and nitrogen additions over the six-year study should provide a good estimate of the carbon sequestration potential of cover crops for remediation of climate change. Objective 1B. In collaboration with a scientist from Middlesex County New Jersey, soil samples were collected from eight fields that received biosolids 25 to 39 years earlier. Soil samples are being processed in the Laboratory. Soil sampling arrangement has been made with scientists from Chicago, Illinois and Blacksburg, Virginia for soil collation from biosolids amended fields. Objective 2A. The first year of a two-year corn-wheat-soybean rotation was completed at one location by applying five rates of labeled fertilizer nitrogen to genetically modified and non-modified corn and measuring corn N uptake and grain yield. The corn’s recovery of the labeled fertilizer nitrogen will provide a direct measurement of the corn nitrogen uptake efficiency. Fall soil samples were also taken before establishing winter wheat in order to trace the labeled nitrogen into the second year’s wheat crop. Chemical analyses of these samples and data summary has begun with the goal of estimating the fertilizer nitrogen additions and removals from a common grain production rotation in the mid-Atlantic region. Objective 2B. A literature search was completed to characterize the ability of common high-residue tillage implements to preserve residue cover and, thereby, reduce erosion, yet provide some degree of soil incorporation of surface-applied manure to reduce manure ammonia volatilization losses. Several tillage implements were identified that could achieve this dual goal, and these implements will be further evaluated with field measurements of residue incorporation using image analysis and ammonia volatilization using wind tunnels. Objective 3A. Studies were made toward quantitative description of phosphorus transformations and bioavailability in manure-amended soils that focused on the turbulent interactions and exchanges that occur between runoff water and the surface of an underlying soil. These studies showed that increased rainfall intensity enhanced transport of colloidal organic phosphorus from surface-applied manure. Research also showed that runoff contained multiple inorganic and organic phosphorus forms that can be as large a fraction as the soluble inorganic phosphorus; and that phosphorus release from an overlaying manure layer underestimated manure phosphorus movement and loss. Objective 3B. Laboratory studies were conducted to determine the impact and mechanisms by which dairy manure decomposition products affect the behavior and transport of phosphorus in soil columns. Studies also looked at the linkage of these decomposition mechanisms to the persistence and continued release of labile phosphorus from past applications of high rates of manure. This research found that manure ligand-like substances significantly enhanced organic phytate-P leaching and that the manure decomposition products suppressed phosphorus breakdown and maintained soluble phosphorus in solution, which enhanced organic phosphorus leaching in the soil. An initial mathematical description of this phenomenon was developed and will be evaluated further to see if this understanding can be applied to improve phosphorus remediation management practices in high-phosphorus soils. Objective 4A. Analyzed field soils to evaluate surface application of mixed amendments of fertilizer, gypsum, and compost. On plots with high application rates, even on very sloping land, both grasses and alsike clover and white sweet clover persisted well. Analysis of soil samples by depth showed that compost applications contained enough calcium to displace the high magnesium and improved rooting depths. Objective 4B. The effect of a double-volume of topsoil vs. layers of topsoil over subsoil was evaluated using the growth and nickel hyperaccumulation of Alyssum corsicum as response variables. Doubling the volume of topsoil increased yield and total nickel in plant shoots, but providing subsoil produced higher nickel accumulations in the shoots. These findings explain the higher nickel accumulation in field grown plants compared to greenhouse pot tests. Different methods of rooting vegetative cuttings were tested as a method to allow possible use of a sterile mutant Alyssum nickel hyperaccumulator plants being developed in a separate project. The growth patterns of cuttings in the first year of growth were dissimilar from plants grown from seeds, although yields were good. Further testing of overwintered transplants will be done to test growth after vernalization. Testing of the sterile mutants was not achieved due to lack of funding. Tests were also conducted to characterize the chemical speciation of nickel in several soils using X-Ray Spectrometry. The tested serpentine topsoils were found to have nickel mostly adsorbed to iron oxides. This research improved the basic understanding of the geology and geochemistry of nickel in serpentine soils. Objective 4C. In collaboration with ARS scientist at Auburn, Alabama, soil and byproduct samples were collected, processed and analyzed for macro and microelements. Soil samples were collected from fields that will be treated with byproduct FGD-gypsum and cropped with peanut and wheat. Completed a cooperative field study to determine if FGD-gypsum surface applied on pastures would adhere to forage plants and possibly cause risks to grazing ruminants from excessive sulfate. Surface applied FGD-gypsum adhered more to tall fescue than to bermudagrass. The first rainfall lowered plant sulfur to non-toxic levels for bermudagrass, but it took rainfalls totaling 1.9 inches to lower the sulfur level of tall fescue. These results indicate that care should be observed with grazing following gypsum application, especially on wide-leaved forages. Objective 4D. In collaboration with Natural Resource Conservation Service (NRCS) from Maryland, Virginia and West Virginia, bulk soils with different physical and chemical properties were identified, collected and processed with sub-samples taken for physical and chemical analysis, and bulk soils were stored for greenhouse experiment.
1. Winter-cereal cover crops can significantly reduce nitrate leaching. Nitrate leaching during the winter water-recharge season is a major pathway for nitrogen loss from agriculture in humid regions. ARS researchers in Beltsville, Maryland, conducted a three-year lysimeter study to compare nitrate leaching losses beneath annual grass covers of rye, wheat, or barley compared to a no-cover control. Nitrate leaching was most affected by the quantity of winter precipitation, with all cover crops reducing nitrate leaching 92% in a low-rainfall winter and 45% in high-rainfall winters. These results are important to farm advisors, farmers, and policy makers because they demonstrate the ability of grass cover-crops to substantially reduce nitrate leaching and thereby improve groundwater quality in humid regions like the Chesapeake Bay watershed.
2. X-ray fluorescence for foliar phosphorus and water status in real time. A rapid spectroscopic method is critically needed that provides real-time, element-specific results to determine nutrient status in fields amended with phosphorus-rich manure. An ARS scientist at Beltsville, Maryland, has shown that in-the-field scans of fluorescence of growing seedlings can be used to obtain instantaneous water and element-specific contents of phosphorus and other mineral nutrients. The crop’s real-time x-ray fluorescence is directly related to the crop’s phosphorus use efficiency, which provides a new paradigm in sustainable nutrient management, and in the development of within-field nutrient management practices that can reduce non-point source nutrient pollution.
3. Gypsum adherence to forage may be a risk for grazing ruminants. Gypsum has long been used to improve soils and crop production, however adverse effects can occur from the direct ingestion of sulfate in gypsum by grazing ruminant animals. A field study by collaborating ARS scientists in Auburn, Alabama, and Beltsville, Maryland, examined the adherence and persistence of FGD-gypsum on bermudagrass and tall fescue, which showed that substantial amounts of gypsum initially adhere to the forages but only persisted on the wider-leaved tall fescue. With tall fescue, gypsum adherence could be observed following a 0.6 inch rain, but not following an additional 1.3 inches of rain. These results indicate that care should be taken with grazing animals following gypsum application, especially on wide-leaved forages, but direct ingestion of gypsum is not likely if grazing is discontinued several weeks and until a rainfall event occurs.
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Torbert III, H.A., Chaney, R.L., Watts, D.B. 2017. Potential adherence of flue gas desulfurization gypsum to forage as a consideration for excessive ingestion by ruminants. Journal of Environmental Quality. 46:431-435.
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