Location: Soil Dynamics Research2019 Annual Report
1. Assess above- and belowground responses of pastures to elevated CO2 and their ability to help mitigate climate change via sequestration of CO2. 1a. Process and publish on biomass (above- and belowground) and soil physicochemical data, inclusive of soil C and N dynamics, from the 10-year CO2/N bahaigrass pasture study. 1b. Plant a Southeastern bermudagrass pasture to determine the effects of atmospheric CO2 level and N management on above- and belowground responses of the plant/soil system. 1c. Process and publish on soil flux of trace gases (CO2, N2O, CH4) from the 10-year CO2/N bahaigrass pasture study. 1d. Plant a Southeastern bermudagrass pasture to determine the effects of atmospheric CO2 level and N management on soil flux of trace gases (CO2, N2O, CH4). 1e. Determine the effects of elevated CO2 on efficacy of herbicidal control of weeds problematic in Southeastern agricultural systems. 1f. Work on effects of elevated CO2 on growth and efficacy of herbicidal control of herbicide resistant weed populations. 2. Manipulate fertilizers, soil amendments such as biochar, and irrigation in ornamental horticultural systems to reduce GHG emission and increase C sequestration. 2a. Identify best management practices (e.g., fertilizer placement, irrigation method) that reduce GHG emissions while optimizing growth for various horticulture crops. 2b. Determine the longevity of carbon in horticultural growth media (e.g., pine bark, clean chip residual, whole tree) following placement in the landscape. 2c. Investigate the effects of biochar in growth media (pine bark) on growth, nutrient retention, and GHG emissions in various ornamental horticultural crops. 3. Develop improved methods to utilize organic waste and soil amendments for soil and crop benefits while minimizing environmental degradation. 3a. Determine the rate of Flue Gas Desulfurization (FGD) gypsum needed to increase corn yield and reduce soluble P concentration in soil. 3b. Determine the rate of FGD gypsum needed to reduce P losses in runoff under no-till and conventional tillage. 3c. Determine the influence of poultry litter as a nutrient source for winter wheat and canola, and its residual effects on succeeding soybean and wheat crops. 3d. Evaluate the influence of poultry litter vs. inorganic fertilizer on crop production under different management practices. 3e. Develop a four-band implement for subsurface band application of pelletized poultry litter, poultry litter, and similar solid manures. The implement will use pneumatic conveying or a similar method to convey the product. 3f. Evaluate effectiveness of subsurface application of poultry litter for row crop production. 4. Develop management practices for economically and environmentally sustainable full life-cycle poultry production systems.
A long-term Southeastern bahaigrass pasture study will be terminated and a bermudagrass pasture study will be initiated. Both systems are exposed to current and projected levels of atmospheric CO2 and either managed (N added) or unmanaged (no N). Carbon flux to plants (biomass growth, allocation, and quality) and soil will be determined with supporting data on soil physicochemical properties. Emphasis will be given to measuring soil C and N dynamics and C storage, root growth, water quality, and GHG (CO2, N2O, and CH4) flux from soil. Using the same CO2 levels, container studies on weeds important to the southeastern U.S. (including those resistant to herbicides) will evaluate herbicide efficacy, regrowth, biomass, and tissue quality. In addition, research will evaluate production practices (in terms of such factors as fertilizer placement, growth media, and irrigation) to identify best management practices which ensure productivity, minimize GHG emissions, and maximize belowground C storage. Other work will examine how the application of organic waste to soil can improve soil conditions via C addition and provide nutrients needed for crop production. Poultry litter may be a viable fertilizer option for crop producers in the Southeastern U.S. given the large amounts of manure generated by the poultry industry. However, improper application of animal waste can contribute to environmental degradation such as increased hypoxia, eutrophication, human health problems, and greenhouse gas emissions. Due to these environmental and animal health concerns, studies will be established to develop improved methods to utilize waste products for animal and crop benefits. In addition, interactions of manure with tillage and cropping systems is not well understood. Thus, the environmental impact of poultry litter addition to soil must be quantified and improved management techniques for application needs to be developed for sustainable use in agriculture. Studies will be initiated to determine long term effects of poultry litter on plant yields, and soil physicochemical properties (including C storage) under various cropping systems. Further, different poultry litter application practices, such as subsurface banding, will be evaluated to determine their impact on nutrient loss and greenhouse gas emissions. Soil amendments (e.g., gypsum) will be evaluated both as a poultry house bedding material and as a soil amendment to determine the impact on animal production, plant responses, and the potential to reduce NH4 emissions and phosphorus (P) loss in runoff. Information acquired in the course of this project will be useful for developing improved poultry and crop production practices. Integrating data from these studies will be economically analyzed to aid understanding on how to adjust future poultry production and agronomic management practices to sustain productivity, while aiding mitigation of global change via increasing soil C sequestration and reducing greenhouse gas emissions.
World food stability depends on productive agricultural systems, but environmental concerns must be addressed for these systems to be sustainable. Research at the ARS-USDA National Soil Dynamics Laboratory, Auburn, Alabama, addresses potential impacts of management strategies on plant productivity, soil physicochemical properties [including soil carbon (C)], greenhouse gas (GHG) emissions, and nutrient losses. Global change research examined the impacts of elevated carbon dioxide (CO2) under differing pasture management practices (nitrogen) on C dynamics. Critical information on how pastures potentially mitigate or contribute to climate change through soil C storage and soil CO2 efflux is needed for efficient environmental management of these systems. During the 10-year bahaigrass pasture study, above- and belowground biomass data have been collected; soil cores for soil C as well as lysimeter solution samples have been collected and are being processed. Aboveground data from the bahaigrass pasture study have recently been accepted for publication. A second long-term bermudagrass pasture study has been initiated. ARS research in Auburn, Alabama, is seeking to understand factors affecting trace gas (carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O)) efflux from agricultural and horticultural systems. Carbon dioxide efflux from the pasture study was continually monitored (24 hours per day) using Automated Carbon Efflux Systems (ACES) for the 10- year duration of the bahaigrass pasture study. Trace gas emissions (CO2, N2O, and CH4) were assessed weekly in this system. Gas samples were collected in situ using the static closed chamber method according to USDA’s Greenhouse Gas Reduction Through Agricultural Carbon Enhancement network (GRACEnet) protocols and analyzed using gas chromatography. In this study, soil C data have also been collected to determine soil C sequestration potential. These same data have begun to be collected in a new bermudagrass pasture study. In addition, a long-term evaluation of CO2 efflux (using ACES) from differing horticulture media has been initiated in plots established on an outdoor soil bin. Further, a horticulture container study evaluating the effects of fertilizer placement and irrigation method on trace gas efflux (using the static chamber method described above) from a woody ornamental has been completed and published. A sun vs. shade ornamental study evaluating trace gas efflux as affected by fertilizer placement has been completed and a publication is currently in journal review. A study of alternative media mixtures using glasshouse-grown annuals to evaluate effects on growth and trace gas emissions has been completed; a publication is currently being drafted. Because of the growing environmental concern regarding organic waste disposal, field and laboratory studies were established to develop improved methods to utilize waste products for soil and crop benefits while minimizing environmental degradation. A series of field studies have been initiated in Alabama to evaluate management practices of fertilizer and poultry litter application methods as affected by tillage systems on crop production, greenhouse trace gas emissions, and nutrient losses to the environment. Research refined management practices for using gypsum application to reduce soluble phosphorus losses to the environment. Research also resulted in an improved in situ, rapid, non- destructive technique of measuring soil C using the inelastic neutron scattering method and compared it to the standard dry combustion method. New methodology was also developed to utilize the inelastic neutron scattering methods in scanning mode to produce soil C distribution maps across a field.
1. Management effects on greenhouse gas emissions in horticulture. Much of the work on reducing greenhouse gas (GHG) emissions and increasing carbon (C) sequestration has been conducted in row crop and forest systems; however, virtually no work has focused on contributions from sectors of the specialty crop industry such as ornamental horticulture. Ornamental horticulture impacts rural, suburban, and urban landscapes. Since little is known about the impact of the horticulture industry on these driving factors, ARS scientists at Auburn, Alabama, have an on-going joint effort with the Horticulture Department at Auburn University to determine baseline GHG emissions, develop strategies to reduce these emissions, and develop strategies to increase soil C storage. A study on the interaction of fertilizer placement (broadcast vs. incorporated) and irrigation method (overhead vs. drip) on growth and GHG emissions from Japanese boxwood demonstrated that both Carbon Dioxide (CO2) and Methane (CH4) loss were not affected by differences in irrigation or fertilizer placement. Findings suggested that utilizing drip irrigation could decrease N2O emissions, regardless of fertilizer placement. However, when limited to overhead irrigation, dibbled fertilizer placement could decrease Nitrogen Oxide (N2O) emissions. This work continues to identify best management practices that can reduce GHG emissions from container produced ornamental crops.
2. U.S. patent method developed for measurement of soil carbon by associated particle imaging. Soil Carbon (C) is critical for farm productivity in terms of water/nutrient retention, good soil structure, and maintenance of clean water through erosion prevention. Further, carbon capture from the atmosphere by plant growth can help mitigate global change through soil C storage. All of these require accurate measurement of soil C which is often time consuming and laborious. ARS researchers at Auburn, Alabama, optimized a new in situ, rapid, non-destructive technique of measuring soil C using the inelastic neutron scattering method (vs. standard dry combustion). Further development of this technique using an associated particle imaging (API) neutron generator with nanosecond precision electronics (patent pending). This API setup can measure alpha-gamma coincidence (timing) spectra, time correlated energy gamma spectra, and energy correlated timing spectra. Test experiments demonstrated that the minimal detectible level (MDL) of carbon is 2.5 times lower with this innovation.
3. U.S. patent method developed for creating soil carbon content maps was developed. Soil carbon (C) mapping is extremely useful in assessing the effect of land management practices on soil carbon storage. ARS researchers at Auburn, Alabama, developed a method of using neutron-gamma analysis in scanning mode for mapping of soil carbon (patent pending). A Global Positioning System (GPS) device and software required to simultaneously acquire gamma signals and geographical positions during scanning operations were added to an existing measurement system. Soil C assessments by the inelastic neutron scattering (INS) method produced reliable soil C maps of agricultural fields using a mobile scanning mode. This method has also been demonstrated to provide reliable C analysis of soil cores using a stationary scanning mode. Findings indicated that the INS method can reliably and rapidly quantify carbon storage in agricultural soils. This critical rapid assessment can be used by scientists to identify best management practices that maintain soil productivity and help mitigate climate change.
4. Poultry litter nutrient content influenced by poultry house management. Poultry litter (PL) has historically been used as a fertilizer for forage and crop production. ARS researchers at Auburn, Alabama, determined that nutrient composition of poultry litter is influenced by management of the poultry houses. Specifically, it was determined that the frequency of clean-out, depth of removal, size of birds reared, and number of flocks raised on the bedding influenced macro and micro nutrient concentrations of the litter. Averaging across all samples collected, PL had a fertilizer grade of 3-3-2 for Nitrogen (N), Phosphorus (P2O5) and Potassium (K2O), respectively. PL collected from broiler production facilities had the highest overall macro- and micro-nutrient concentrations, while PL from compost had slightly higher N, P and Calium (Ca) and lower Carbon (C) than PL taken directly from houses or drystack barns. Nutrients tended to be higher in caked PL than PL from the entire six-inch depth. PL nutrients tended to increase with flocks and decrease with frequency of clean-out.
5. Fertilizer management using poultry litter studied in double cropping systems. Poultry litter (PL) application and double cropping are management practices that could be used with conservation tillage to increase yields compared with conventional mono-cropping systems. ARS researchers at Auburn, Alabama, evaluated winter wheat (Triticum aestivum L.) and soybean [Glycine max (L.) Merr.] yield response to PL alone and combinations of PL and inorganic Nitrogen (N) versus inorganic N alone when applied to the winter wheat in a double-cropping system. Fertility treatments for winter wheat included an unfertilized control, 120 lb/acre inorganic N fertilizer, PL at the rate of 40 lb/N acre plus 80 lb/acre inorganic N, PL at the rate of 80 lb N/acre plus 40 lb/acre inorganic N, and PL at the rate of 120 lb N/acre. An unfertilized winter fallow treatment was also included to enable a comparison of yield between the mono- and double-cropped soybean. A combination of PL and inorganic N resulted in wheat yields comparable to those with inorganic N alone while PL alone yielded less. Double-cropping soybeans with winter wheat tended to improve soybean yield when compared with mono-cropped soybeans planted on the same date; however soybean yield was not consistently enhanced by the residual PL nutrients applied to wheat when compared with N fertilizer only treatment.
6. Soil shear strain model is expected to be useful in analysis of soil-machine interactions. Soil compaction limits crop roots from reaching more soil to access water and nutrients, and reduces rates of water infiltration into soil, causing increased soil erosion. In continuum mechanics, strains are classified as either normal strains or shear strains. A normal strain occurs along a direction perpendicular to the face of an element and a shear strain is along a direction parallel to the face. Equations (models) which describe soil compaction can be developed using soil triaxial tests conducted in a lab. Using triaxial test data from a clay and a clay loam soil, equations which relate shear strain to the maximum natural shear stress, the major principal stress, and the natural volumetric strain were developed by ARS researchers at Auburn, Alabama. This model of maximum natural shear strain when coupled with a model of natural volumetric strain developed previously, should be valuable for finite element analysis of soil response to applied loads. The shear strain model is expected to be useful in numerical methods, including finite element analysis, applied to interactions of mechanical components such as tires, rubber tracks or steel tracks of vehicles, and tillage components, with soil. The model should be useful in the design and analysis of agricultural and construction equipment, through improving the application of modeling to soil-machine interactions, thereby promoting the accuracy and usefulness of simulation for development of agricultural and construction equipment.
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