Location: Soil Dynamics Research2017 Annual Report
Objective 1: Assess above- and belowground responses of pastures to elevated CO2 and their ability to help mitigate climate change via sequestration of CO2. Sub-Objective 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. Sub-Objective 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. Sub-Objective 1c: Process and publish on soil flux of trace gases (CO2, N2O, CH4) from the 10-year CO2/N bahaigrass pasture study. Sub-Objective 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). Sub-Objective 1e: Determine the effects of elevated CO2 on efficacy of herbicidal control of weeds problematic in Southeastern agricultural systems. Sub-Objective 1f: Work on effects of elevated CO2 on growth and efficacy of herbicidal control of herbicide resistant weed populations. Objective 2: Manipulate fertilizers, soil amendments such as biochar, and irrigation in ornamental horticultural systems to reduce GHG emission and increase C sequestration. Sub-Objective 2a: Identify best management practices (e.g., fertilizer placement, irrigation method) that reduce GHG emissions while optimizing growth for various horticulture crops. Sub-Objective 2b: Determine the longevity of carbon in horticultural growth media (e.g., pine bark, clean chip residual, whole tree) following placement in the landscape. Sub-Objective 2c: Investigate the effects of biochar in growth media (pine bark) on growth, nutrient retention, and GHG emissions in various ornamental horticultural crops. Objective 3: Develop improved methods to utilize organic waste and soil amendments for soil and crop benefits while minimizing environmental degradation. Sub-Objective 3a: Determine the rate of Flue Gas Desulfurization (FGD) gypsum needed to increase corn yield and reduce soluble P concentration in soil. Sub-Objective 3b: Determine the rate of FGD gypsum needed to reduce P losses in runoff under no-till and conventional tillage. Sub-Objective 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. Sub-Objective 3d: Evaluate the influence of poultry litter vs. inorganic fertilizer on crop production under different management practices. Sub-Objective 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. Sub-Objective 3f: Evaluate effectiveness of subsurface application of poultry litter for row crop production.
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, re-growth, 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 in the landscape for various horticulture crops. 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 and the rising costs of inorganic fertilizers. However, improper application of animal manures in agriculture can contribute to environmental degradation such as increased hypoxia, eutrophication of surface waters, human health problems, and greenhouse gas emissions. Due to these environmental concerns, field and laboratory studies will be established to develop improved methods to utilize waste products for soil and crop benefits while minimizing environmental degradation. 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 tillage and 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 to determine the impact on plant responses and the potential to reduce phosphorus (P) loss in runoff. Information acquired in the course of this project will be useful for developing agricultural practices using poultry litter as a nutrient source for environmentally sustainable plant production. Integrating data from these studies will aid understanding on how to adjust future 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 bahiagrass pasture study, above- and belowground biomass data have been collected and are being analyzed; soil cores for soil C as well as lysimeter solution samples have been collected and are being processed. ARS research in Auburn, Alabama, is seeking to understand factors affecting trace gas (carbon dioxide (C), 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 this 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. In addition, 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, data analyzed, and a publication is 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. A patented methodology to use soil microbial inoculants to not only improve plant production but also reduce nitrous oxide emissions from fertilizer nitrogen applications were studied. Research resulted in the development of a new method for measurement of ammonia (NH3) volatilization losses from agriculture. Research also resulted in a new 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.
1. Response of a southeastern pasture system to elevated CO2 evaluated. Although much is known about plant responses to rising atmospheric CO2 levels, how pasture systems in the southeastern U.S. will respond to predicted future atmospheric CO2 concentrations remains unstudied. Researchers at the National Soil Dynamics Laboratory, Auburn, Alabama, determined above- and belowground biomass in a bahiagrass pasture exposed to ambient or elevated CO2 and either managed (with nitrogen (N) addition) or unmanaged (no N addition) for 10 years. Soil water, carbon and nitrogen have also been determined in this study. To date, results show that plant biomass only shows a positive response to elevated CO2 when nitrogen is added. Data from this study will add to the understanding of plant responses to rising atmospheric CO2 which will be useful for modelers and policy-makers. Results will also be of use to producers and may indicate a need to shift from unmanaged to managed systems to take advantage of the rising level of atmospheric CO2 for increased productivity and profitability.
2. A new technology to measure soil carbon by inelastic neutron scattering methodology developed. Maintaining a suitable soil carbon (C) content is a critical factor for farm productivity in terms of water/nutrient retention, good soil structure, and maintenance of clean water through erosion prevention. Further, C 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. Researchers at Auburn, Alabama, refined a new in situ, rapid, non-destructive technique of measuring soil C using the inelastic neutron scattering (INS) method and compared it to the standard dry combustion method. Soil C assessments by these two methods demonstrated the INS method produced reliable and comparable measures of soil C at depths of 0-10 cm. Results indicated that this new INS method can more rapidly quantify carbon storage in agricultural soils. This new technology for rapid soil carbon assessment can be used by scientists to identify best management practices that maintain soil productivity and help mitigate climate change.
3. Elevated atmospheric carbon dioxide (CO2) levels and nitrogen fertilization impact soil pore structure. Soil structure is critical to water retention, plant rooting, and other belowground processes. However, it is not well understood how high atmospheric CO2 affects soil structure in agricultural systems. Researchers at Auburn, Alabama, in collaboration with university colleagues analyzed soil aggregate fractal properties supported by 3D microtomographic imagery from a long-term bahiagrass pasture exposed to elevated atmospheric CO2. Nitrogen (N) fertilization increased intra-aggregate porosity and pore space in larger aggregates. These effects were enhanced by elevated CO2, yielding an increase in water retention at pressure potentials near the wilting point of plants. This did not occur under elevated CO2 without N addition. Results suggest that soil pore structure could undergo N-dependent changes as atmospheric CO2 increases. This may have global-scale implications for water balance, carbon storage, and related belowground functions, which is important for climate modelers and scientists particularly if drought increases as predicted.
4. Gypsum found to be an effective bedding material in houses for poultry broiler production. Phosphorus (P) loss from agricultural fields has been implicated as the major cause of surface water eutrophication, especially fields receiving manure or poultry litter applications. ARS researchers at Auburn, Alabama, have shown that gypsum can be used as a management tool to reduce dissolved P losses with surface water runoff and has led to the USDA–NRCS creating a National Conservation Practice Standard (333, Amending soil properties with gypsum products). Presently, the recommended practice for reducing P loss from agricultural fields receiving manure or poultry litter is to apply gypsum on top of the manure source in a second operation, which increases the costs for the producer. The most effective approach to optimize P reduction would be to mix it directly with the manure source but adds cost associated with mixing. However, if gypsum was used as the bedding material for poultry production, then the manure and gypsum mixture would be part of the poultry litter when it is cleaning out the poultry houses. A study was conducted to evaluate the effectiveness of using gypsum as a bedding material for broiler production and results indicate that gypsum provided some positive benefits for broiler production. In this study, gypsum was compared to pine shavings (standard bedding) in three successive research trials/flocks (5 lb. birds with no decaking). While small decreases were noted for body weight and adjusted feed efficiency in flock 1 with gypsum, they were similar in flocks 2 or 3. Mortality was lower with gypsum bedding for flock 3 and footpad lesions and ammonia volatilization were also lower with gypsum (flock 1). The reduction in ammonia volatilization could result in lower production cost. Overall, these results showed that gypsum has promise as an alternative bedding material for poultry broiler production.
5. Application of gypsum to reduce dissolved reactive phosphorus (DRP) losses to the environment examined for management concerns. There are growing concerns regarding the fate of nutrients, especially P, from land application of animal waste. One approach to reduce runoff losses of P is to treat manure or the soil receiving manure with chemical amendments such as gypsum. ARS researchers at Auburn, Alabama, have shown that gypsum use with poultry litter can be an effective method of reducing DRP losses to the environment. However, other concerns regarding gypsum utilization had not been addressed. Research was conducted regarding the potential increased losses of soil macro and micro nutrients with the use of gypsum as well as research to examine the potential for toxicity issues from excessive ingestion of gypsum by ruminants. Results from this work indicated that while these problematic issues exist under conditions of mismanagement, no concerns exist with the application of gypsum as outlined in the USDA- National Resources Conservation Service Conservation Practice Standard 333. Amending soil properties with gypsum products and gypsum use would be beneficial for agriculture production and the environment.
6. A United States Patented method of using microbial inoculants to reduce nitrous oxide (N2O) emissions associated with nitrogen (N) fertilizer application was demonstrated. ARS researchers at Auburn, Alabama, have identified microbial inoculants that can improve plant production and improve plant nutrient efficiency. Of particular interest is the development of a microbial inoculants that will also reduce N2O losses form fertilizer nitrogen use. The loss of N2O is of particular concern not only because of the loss of N so that plants cannot use it, but also due to its potential to contribute to global warming. Over the past few decades, N2O emissions have increased worldwide due to several factors, including increases in cultivated crop area, excessive applications of N fertilizers, and livestock production. But losses of N2O from fertilizer is considered to be the largest contributor to global warming from agriculture as a whole. Ongoing research led to the discovery that specific soil microorganisms applied with the correct fertilizer can reduce N2O emissions, which was the bases of the patent. As a result, new management tools were developed to reduce N2O emissions from production agriculture.
7. New method for measuring ammonia (NH3) volatilization in field studies developed. Ammonia volatilization from agricultural systems can be a significant mechanism of nitrogen (N) loss from soil. In addition to concerns of losing soil N, NH3 is an air pollutant. ARS researchers at Auburn, Alabama, developed and validated a low cost method for measurement of NH3 volatilization losses for use in static chambers. This method utilizes glass tubes coated with a chemical that absorbs NH3 from the air and can be used as a predictor for the actual air concentration. Use of this procedure is advantageous in that it can be used to measure NH3 from small research plots and allow for comparisons of NH3 emissions from a large number of treatments without having several large scale field experiments. When using this method, a minimum of one correction factor is needed to convert from the NH3 concentration measured with the glass tube to the actual NH3 concentration. In addition, if a material that absorbs NH3 is used in the construction of the static chamber, another correction factor will need to be applied. Values measured with this technique can be used to estimate NH3 efflux rates and to determine the efficacy of agricultural fertilizer application practices.
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