2009 Annual Report
1a.Objectives (from AD-416)
1. Identify the physical and chemical characteristics of manure and soil-manure interactions that influence phosphorus transformations to determine controlling mechanisms of phosphorus mobilization and bioactivity.
2. Develop rapid and accurate on-farm measurement tools to quantify bioactive phosphorus in manure and manure amended soils for managing whole-farm phosphorus balance.
3. Develop zeolitic materials and other by-products and novel methods for phosphorus immobilization, removal, and recovery from manure based on bioactive phosphorus chemistry and mechanisms of phosphorus mobilization.
4. Develop manure and soil parameters and module that links organic phosphorus transformations to the cycling of carbon and nitrogen to refine the Root Zone Water Quality model.
1b.Approach (from AD-416)
An integrated approach involving laboratory and field research and modeling will be used to improve the understanding of phosphorus transformations, mobilization, and fate to control its environmental losses. A comprehensive study of phosphorus mineralization in manure and manure-amended soils will be conducted. Improved quick tests by infrared spectroscopy and biological assays and modeling and decision-support tools, will be developed to evaluate effects of manure management practices on soil active and time-dependent phosphorus pools. Immobilization and recovery of phosphorus by zeolitic materials and evaluations of the potential re-solubilization of phosphorus that was immobilized using soil and manure additives will be made to add to whole-farm management options.
Recent studies indicate that soil extractable phosphorus and phosphorus in runoff are greatest immediately after fertilizer and manure applications. ARS scientists conducted a study to evaluate changes in phosphorus pools in soils amended with cattle manure and phosphate fertilizer throughout a single growing season. Various forms of bioactive phosphorus present in soil were determined periodically during two growing seasons of grain sorghum. Three soil inorganic and organic phosphorus fractions were differentiated to evaluate the in-season changes in these pools in fertilized and manure-amended soils. There were distinct seasonal fluctuations in soil concentrations of exchangeable and enzyme-labile phosphorus, which all peaked during the warmer months of the season. Current pre-plant phosphorus recommendations and fertilization practices should be reevaluated for mitigating potential environmental impact of spikes of elevated level of soluble soil phosphorus; such a buildup was predicted by in-season mineralization of organic phosphorus of soil or manure or other forms of organic soil amendments.
In-season variations in phosphorus solubility and availability also pointed to the need for real-time detection and precision management of phosphorus and other plant nutrient inputs on the farms. In FY 2009, X-ray fluorescence spectroscopy was applied to determine phosphorus and other minerals, such as potassium, iron, aluminum, and calcium, in animal manure and soils. The high throughput and multi-element and elemental specificity of x-ray fluorescence was well adapted as a detection tool for on-farm applications, for detection of temporal and spatial changes in phosphorus content, and for precision management of soil mineral nutrients. A small portable x-ray fluorescence spectrometer was also evaluated; limits of detection for mineral elements of agronomic importance were compared to a laboratory-scale x-ray spectrometer. Phosphorus measurement conditions are being developed to optimize sensitivity and accuracy of the portable instrument for variable matrix characteristics and inter-element interactions. The cost and time savings of soil testing and near-real time results can be substantial and will lead to more environmentally friendly and sustainable nutrient management practices. The x-ray spectrometric approach will contribute to a potential real-time phosphorus sensing system. Such a system will enhance manure and soil nutrient management decisions on the farm, producing optimal crop responses while minimizing soil phosphorus buildup or surpluses that may result in offsite discharges and water quality impairment.
Availability of phosphorus in soils amended with water-treatment residuals. Soil phosphorus that has been sequestered by industrial and municipal byproducts high in aluminum, calcium, and iron can be released when a reduction in soil pH or flooding occurs for extended periods. This potential release of phosphorus may produce undesired effects such as movement from crops and water impairment. Plant-available phosphorus that was immobilized in the amended Matapeake soil did not become soluble after acidification and when seeded to Bermudagrass. Although soluble aluminum and iron in soil were higher after acidification, they were not at levels that would negatively affect grass growth and the environment.
Large spikes in phosphorus availability during a growing season. Soil extractable phosphorus and phosphorus in runoff are greatest immediately after fertilizer and manure applications. Changes in phosphorus pools in soils amended with beef cattle manure and fertilizer were examined throughout a single growing season. Distinct seasonal fluctuations were observed in soil concentrations of exchangeable and total bioactive enzyme-labile phosphorus which all peaked during the warmest month of the season. Current pre-plant phosphorus recommendations should be reevaluated as a means to mitigate the negative environmental effects of soluble soil phosphorus spikes caused by in-season mineralization of organic phosphorus forms. Sustainable precision nutrient management practices that take into account variations in phosphorus availability must be developed to accommodate weather uncertainties over an entire growing season and in-season changes in phosphorus availability.
Soil transformations of immobilized phosphorus and phosphorus uptake in two grain legumes. Reduction in the availability of immobilized phosphorus to growing plants is a concern to producers. The ability of soybean and pigeon pea crops to utilize manure phosphorus immobilized by iron-rich byproducts was evaluated. These grain legume crops can access poorly available forms of phosphorus by secreting organic compounds that can dissolve bound iron phosphates. At all amendment rates tested, iron was found not to affect crop yield. Plant phosphorus was taken up from the inorganic phosphorus fraction and the soil organic enzyme-labile phosphorus pool replenished these mineral phosphate fractions. Therefore, iron-rich byproducts can be used to reduce soluble phosphorus in amended soils to reduce agricultural phosphorus entering the Chesapeake Bay or similarly vulnerable ecosystems.
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Rao, S.C., Dao, T.H. 2008. Relationships Between Immobilized Phosphorus Uptake in Two Grain Legumes and Soil Bioactive P Pools in Fertilized and Manure-Amended Soil. Agronomy Journal. 100:1535-1540.
Dao, T.H., Guber, A.K., Sadeghi, A.M., Karns, J.S., Van Kessel, J.S., Shelton, D.R., Pachepsky, Y.A., Mccarty, G.W. 2008. Loss of Bioactive Phosphorus and Enteric Bacteria in Runoff from Dairy Manure Applied to Sod. Soil Science. 173:511-521.
Codling, E.E. 2008. Effects of Acidity and Cropping on Byproduct Immobilized Phosphorus Solubility and Extractable Aluminum, Calcium and Iron From Two High Phosphorus Soils. Soil Science. 173:552-559.
Reeves III, J.B. 2009. Does Spectral Format Matter in Diffuse Reflection Spectoscopy. Applied Spectroscopy. 63:669-677.
Codling, E.E., Chaney, R.L., Mulchi, C.L. 2008. Broiler Litter Management Practices: Effects on Phosphorus, Copper, Zinc, Manganese and Arsenic Concentrations in Maryland Coastal Plain Soils. Communications in Soil Science and Plant Analysis. 39(7&8):1193-1205.