Location: Soil Dynamics Research2018 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 (NSDL), 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 and are being analyzed; soil cores for soil C as well as lysimeter solution samples have been collected and are being processed. 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, data analyzed, and a publication has been submitted. A sun vs. shade ornamental study evaluating trace gas efflux as affected by fertilizer placement has been completed. A study of alternative media mixtures using glasshouse-grown annuals has been initiated to evaluate effects on growth and trace gas emissions. 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 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, including examining potential negative impacts from the gypsum application. This also included research on using gypsum as a bedding material in poultry houses to facilitate the mixing of the gypsum with the manure. A patented methodology to use soil microbial inoculants to not only improve plant production but also reduce nitrous oxide emissions from fertilizer nitrogen applications was studied and an economic evaluation of commercialization within the C trading market was conducted. Research also resulted in the optimization of a new in situ, rapid, non-destructive technique for measuring soil C using the inelastic neutron scattering method developed at the National Soil Dynamics Laboratory. Soil C assessments by the Inelastic neutron scattering (INS) method produced reliable soil C measurements in both a stationary and mobile scanning mode and findings indicated that the INS can reliably and rapidly quantify C storage in agricultural soils.
1. Response of industrial sweet potato to elevated carbon dioxide (CO2). Rising atmospheric CO2 concentration can increase plant growth, yield, and resource use efficiency, but how this might affect industrial sweet potatoes (Ipomoea batatas) grown for bioethanol production is unknown. ARS researchers at Auburn, Alabama, exposed an industrial sweet potato variety to ambient or elevated CO2. Growth in elevated CO2 increased above- and belowground biomass production. In particular, tuber dry weight increased by 41% compared with plants grown in ambient CO2. Industrial sweet potatoes have potential as a source for bioethanol production, which can be enhanced by rising atmospheric CO2. Data from this study will add to the understanding of plant responses to rising atmospheric CO2 that will be useful for modelers and policy-makers. Results will also be of use to bioethanol producers in identification of new crop varieties that may enhance production capabilities.
2. Measurement of soil carbon by inelastic neutron scattering. 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 (INS) method (vs. standard dry combustion). Soil C assessments by the INS method produced reliable measures of soil C in both a stationary and a mobile scanning mode. Monte-Carlo computer simulations were also used to refine operational settings. 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.
3. Aspects of soil fertility in subtropical Brazil. Soil fertility is critical for maintaining plant productivity to meet future demands for food and fiber. In collaboration with Brazilian scientists, ARS researchers at Auburn, Alabama, investigated fertility aspects of soil and plant tissue in Brazilian systems. Findings showed that soil Phosphorus and Potassium availability affects elemental accumulation in tissues of a socially and economically important endangered Brazilian conifer. Other findings identified soil groups that can aid in soil acidity management to optimize crop productivity in southern Brazil. This work is important to growers for identifying and maintaining good fertility management practices to help them meet future demands for food and fiber in this region of South America.
4. A meta-analysis statistical methodology used to study the influence of poultry litter use in crop production. There is a large body of work showing that poultry litter (PL) can be used as a nutrient source for crop production. However, the yield responses evaluated in these studies often varied when compared to inorganic fertilizer (IF) sources depending on soil type, management conditions, and PL application practices. ARS researchers at Auburn, Alabama, conducted a comprehensive review of 90 studies consisting of 866 observations from the scientific literature using meta-analysis (statistical methods that are used to combine results from multiple studies to identify common effects). Synthesis of this scientific literature showed that the beneficial effect of PL when compared to IF was greater in acidic soil than neutral or alkaline soils, and greater in medium textured soils such as loams compared to light-textured sands or heavy-textured clays. The effect of PL application was also influenced by tillage, with conservation tillage providing the greatest improvement to crop productivity. Application rate, timing, and method influenced crop productivity. The greatest benefits were observed when PL was applied at the highest application rate, applied greater than 10 day before sowing, applied during consecutive years, and applied as surface broadcast or subsurface banded beside the crop row rather than incorporated with tillage. Overall, this comprehensive quantitative review showed that PL is comparable to inorganic nitrogen; however, the greatest benefits were observed with long-term annual (3 or more) litter applications. Results from this study will aid extension personnel and agricultural land practitioners in making prescriptions for poultry litter use in crop production systems.
5. Poultry litter placement affects seedling emergence and early growth stage of corn. Poultry litter (PL) has historically been applied to the soil surface for forage and crop production. This practice can leave the phosphorus (P) susceptible for loss with surface water runoff, which may lead to water quality degradation. Recently, technology for applying PL in bands below the soil surface has been developed to minimize the susceptibility of P loss with runoff water, from the litter. However, it was unclear whether planting corn in or near the PL bands would negatively or positively influence seed germination and seedling growth. This information is needed for recommending to producers the lateral distance required to minimize seedling damage when subsurface banding PL next to planted crop rows. ARS researchers at Auburn, Alabama, conducted a study to evaluate PL band placement on seedling emergence and early stage plant growth of corn. Results indicated that placing corn seeds 5 cm to the side of subsurface PL bands resulted in seed germination rates and early stage plant growth similar to that of surface-applied PL (standard practice). In contrast, seeding directly into subsurface PL bands dramatically reduced corn seedling emergence and inhibited early stage plant growth and root system establishment. Results from this study will aid extension personnel and agricultural land practitioners in recommending that planting corn seeds 5 cm to the side of subsurface PL bands as compared to planting directly in the bands.
6. Gypsum found effective as bedding material in broiler production houses. 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-Natural Resource Conservation Service creating a National Conservation Practice Standard (333, Amending soil properties with gypsum products). Presently, the recommended practice 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 bedding material in the poultry house, the mixing of the manure and gypsum would occur as a part of the process of cleaning out the poultry manure from the houses. ARS researchers at Auburn, Alabama, conducted a study to evaluate the effectiveness of using gypsum as a bedding material for broiler production by comparing gypsum to pine shavings (standard bedding) in three successive research trials/flocks (5 lb. birds with no decaking). Results indicate that gypsum provided some positive benefits for broiler production. 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.
7. Application of gypsum reduces phosphorus (P) losses to the environment. 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 P losses to the environment. However, other concerns regarding gypsum utilization have not been addressed. ARS researchers at Auburn, Alabama, conducted research 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.
8. No heavy metal contamination found from agriculture application of flue gas desulfurization gypsum. Recently, industrial byproducts flue gas desulfurization (FGD) gypsum is being used as a soil amendment in agriculture as outlined by the USDA-Natural Resource Conservation Service Conservation Practice Standard (333, Amending soil properties with gypsum products). However, concerns regarding heavy metal contributions to the environment from FGD gypsum use have arisen. ARS researchers at Auburn, Alabama, conducted a study to examine the impact of FGD gypsum application on soil, plant, and runoff when applied alone or with poultry litter contributing potentially toxic elements to pastures. Plant, soil, and runoff samples were analyzed for heavy metals and results indicated that FGD gypsum application would not result in increased heavy metal concentrations. In addition, the application of FGD gypsum significantly reduced P, As, and Fe concentrations in runoff indicating that FGD gypsum can reduce the negative impact of manure surface application on surface water degradation. The results of this study are being used by the U.S. EPA to conduct a risk evaluation of FGD gypsum use in agriculture for use in the regulation of this industrial waste.
9. U.S. patented method developed for using microbial inoculants to reduce nitrous oxide (N2O) emissions from nitrogen fertilizer application. 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 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 nitrogen (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 from agriculture as a whole. Ongoing research lead to the discovery that specific soil microorganisms applied with the correct fertilizer can reduce N2O emissions, which was the bases of the patent (US 9,266,786 B2). As a result, new management tools were developed to reduce N2O emissions from production agriculture which can be used by producers as a income stream in the carbon trading market to reduce greenhouse gas impacts.
10. Planter closing wheel type found to not influence cotton emergence. Closing wheels on a row crop planter help provide good seed-soil contact during planting and can influence emergence and crop stand. Various types of closing wheels are available to producers for use on planters, but very little research has documented how these implements perform in southeastern U.S. soils in conservation tillage systems. ARS researchers at Auburn, Alabama, evaluated seven closing wheel types used on a row crop planter planting cotton in a conservation tillage system during a three-year study on a sandy loam soil and a clay soil. Cotton was planted into a rye cover crop which had been rolled prior to cotton planting. The planter closing wheel type did not significantly affect emergence of cotton plants at 10 days after planting. Cast iron closing wheels provided the greatest cotton plant emergence, but the difference was not statistically significant from the other closing wheel types. Results from this study indicate that producers' choice of planter closing wheels will not greatly impact planter performance.
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