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United States Department of Agriculture

Agricultural Research Service

2008 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.

3.Progress Report
NUTRIENT RELATIONSHIPS IN THE TURNOVER OF DAIRY MANURE PHOSPHORUS: In FY 2008, ARS scientists conducted a study of the transformations of phosphorus in dairy manure, which contained a range of specific nutrient ratios. Phosphorus in manure and other organic by-products occurs along side with other macronutrients, namely nitrogen and carbon. Interactions among manure nutrients alter each other’s behavior and fate. Manure nutrient composition was determined periodically according to the ligand-based enzymatic fractionation assay developed by the EMBUL laboratory. Preliminary results showed that the interactions between macronutrients affected the rates of transformations of inorganic and organic phosphorus forms and the carbon gaseous losses to the atmosphere. Current manure management practices may be necessary to minimize gaseous emissions during processing and storage and conserve carbon, nitrogen, and organic phosphorus forms to derive the most benefits from recycling manure in crop production. New knowledge of element interactions is applied to a new module of phosphorus transformations under development. The progress made addressed the needs of National Program 206, Nutrient Component II (Nutrients) and Problem Statement II-c (Management Tools for Indexing and Evaluating Nutrient Fate and Transport).

RAPID AND ACCURATE ON-SITE PHOSPHORUS MEASUREMENT TOOLS: In FY 2008, portable x-ray fluorescence spectrometry is evaluated and limits of detection for mineral elements of agronomic importance are compared to laboratory-scale instrumentation. Phosphorus measurement conditions are being developed to optimize sensitivity and accuracy of the portable instrument for variable matrix characteristics and inter-element effects. The approach will contribute to a potential real-time phosphorus sensing system that enhance manure and soil nutrient management decisions on the farm for producing optimal crop responses while minimizing soil phosphorus buildup and offsite discharges. The progress made addressed the needs of National Program 206, Nutrient Component II (Nutrients) and Problem Statement II-c (Management Tools for Indexing and Evaluating Nutrient Fate and Transport).

1. Tying up soluble phosphorus with manure additives rich in aluminum or iron have received a lot of interest to lower soluble phosphorus concentrations in manure or manure-amended soils. As concerns of reduction in availability of immobilized phosphorus to growing plants prevail, ARS scientists conducted field pot studies to evaluate the ability of pigeon pea and soybean crops to utilize manure phosphorus immobilized by iron compounds. These grain legume crops can access poorly available forms of phosphorus by chemically altering the rhizosphere through exudation of organic compounds that can dissolve bound iron phosphates. Changes in soil bioactive phosphorus were determined at three growth stages of the legumes using a novel ligand-based enzymatic fractionation procedure. The addition of manure phosphorus was beneficial to plant dry matter yield and phosphorus uptake. The iron amendment did not affect plant dry matter production at all rates.At the whole plant level, the suppression of phosphorus solubility and therefore plant uptake was effective at the 3 to 1 iron:phosphorus rate of iron addition, in spite of the legume root system’s ability to dissolve iron phosphates. Non-cropped soil showed that organic enzyme-labile phosphorus pool replenished these water-soluble and insoluble mineral fractions. Conventional soil test estimates were not correlated with whole plant uptake and therefore do not reflect the plant availability of immobilized phosphorus as well as the enzymatic assay. The accomplishment addressed the needs of National Program 206, Nutrient Component II (Nutrients) and Problem Statement II-c (Management Tools for Indexing and Evaluating Nutrient Fate and Transport) and IV-a (Phytoavailability and Bioavailability of Nutrients, Trace Elements and Xenobiotics in Byproducts Considered for Beneficial Use).

2. IN-SEASON CHANGES IN PHOSPHORUS AVAILABILITY: ARS scientists conducted a field study to evaluate changes in phosphorus pools in soils amended with cattle manure and phosphate fertilizer throughout a single growing season. Grain sorghum was planted after fertilizer applications and received supplemental irrigation. Various forms of bioactive phosphorus present in soil were determined periodically during two growing seasons. Three phosphorus fractions were differentiated, i.e., manure water-extractable phosphate, exchangeable inorganic phosphates, and the all-inclusive total bioactive phosphorus to evaluate the in-season changes in these pools for commercial fertilizer and cattle manure applications. There were distinct seasonal fluctuations in soil concentrations of exchangeable inorganic phosphates and total bioactive phosphorus, which all peaked during the warmest month of the season. Current phosphorus fertilization practices may need to be adjusted for mitigating potential environmental impact of temporarily elevated levels of soluble phosphate such a buildup was predicted by in-season mineralization of organic phosphorus of soil or manure or other forms of organic amendment. Sustainable nutrient management practices that take into account variations in phosphorus availability must be developed to accommodate weather uncertainties over an entire growing season, in-season changes in soil and manure phosphorus availability, and extensive small-scale spatial variability of soil properties to mitigate risks of phosphorus loss to the environment. The accomplishment addressed the needs of National Program 206, Nutrient Component II (Nutrients) and Problem Statement II-c (Management Tools for Indexing and Evaluating Nutrient Fate and Transport).

3. Animal manure is applied to rangeland and hay fields to improve nutrient status andphysical properties of the underlying soil, and eventually forage production andforage quality. However, surface-applied manure on grassland is susceptible to loss in runoff, depending on factors that include slope, compaction, soil hydraulic properties, and plant factors such as plant density, and the state of the grass stand. ARS scientists conducted rainfall simulation studies to determine the concurrent release and transport of manure-borne phosphorus and bacteria from grass-applied manure. Under simulated rain, a continuum of particle sizes, between 0.1 and100 micrometers, was detected in runoff throughout the 90-min simulation. The study results demonstrate the manure-borne bacteria werereleased to runoff while associated with organic P-containing manure particulates. Clearly, raindrop’s impact energy must be attenuated by a well-maintained live vegetative cover. Live leaf blade’s surface roughness and structural features such as leaf hairs play an important role in impeding the release of bacteria and particulate-associated phosphorus forms to runoff. Dead grass dry matter had no filtering effect, transporting manure-borne contaminants unstrained. Given the micrometer size range of suspended particles, losses of colloidal particulate phosphorus and colloid-associated bacteria may extend well beyond the immediate vicinity of the depositedmanure. The accomplishment addressed the needs of National Program 206, Component II (Nutrients) and Component III (Pathogens) and Problem Statement II-c (Management Tools for Indexing and Evaluating Nutrient Fate and Transport).

4. Phosphorus management is currently based on a pre-plant soil test approach which cannot accommodate weather uncertainties over an entire growing season and during-season changes in phosphorus availability. Soil microbiological activity variations can profoundly affect the rates of transformation and protracted release of phosphate depending upon the kind of organic phosphorus species and their biochemical microenvironment. Many current analytical methods are not conducive to rapid analysis of a large number of replicates to accurately quantify phosphorus content of heterogeneous materials such as manures. The variability undermines the accuracy of land application rates and optimal allocation of manure-borne constituents on the field, the whole farm, or in thewatershed. Simultaneous multi-element analysis by an X-ray fluorescence method wasdeveloped to measure phosphorus non-destructively in the laboratory. Other mineralnutrients as well as trace elements that are of agronomic importance are alsodetermined. Over 500 millions broilers are produced annually in the Delmarva region, and each bird generates close to 2000 lbs of dry litter/year. This litter variedwidely in nutrient content as well as mineral dietary supplements such as arsenic andcopper. Feed ingredient analyses showed the enrichment of enzyme-labile phytate-phosphorus in poultry litter. The pool of enzyme-labile organic phosphorus formrepresents a sizable phosphate source under biological controls and contributes tothe long-term supply and release of soluble phosphorus from poultry litter. The accomplishment addressed the needs of National Program 206, Nutrient Component II (Nutrients) and Problem Statement II-c (Management Tools for Indexing and Evaluating Nutrient Fate and Transport).

5. AVAILABILITY OF PHOSPHORUS IN SOILS AMENDED WATER-TREATMENT RESIDUALS: In FY 2008, ARS scientist investigated the concern about the potential release of soil phosphorus that has been sequestered by industrial and municipal byproducts high in aluminum, calcium and iron if the environmental conditions such as a reduction in soil pH or flooding were to occur for extended periods. These byproducts have been shown to be effective in reducing water-soluble phosphorus in phosphorus-enriched soils. Two soils were amended with water-treatment residuals were subjected to either flooding to induce anaerobic conditions or to the lowering of the soil pH. Results showed that phosphorus sequestered by these byproducts did not become soluble when the byproduct-amended soils were exposed to cropping under acidic or anaerobic conditions. It was concluded that these byproducts can be used to reduce the amount of soluble phosphorus that may be discharged from amended soils to possibly reduce the amount of agricultural phosphorus entering the Chesapeake Bay. The accomplishment addressed the needs of National Program 206, Nutrient Component IV (Byproducts) and Problem Statement IV-a (Phytoavailability and Bioavailability of Nutrients, Trace Elements and Xenobiotics in Byproducts Considered for Beneficial Use).

5.Significant Activities that Support Special Target Populations
During FY08, scientists of the Environmental Microbial Safety Laboratory at BARC adopted the bioactive phosphorus methodology to evaluate the release and transport of fecal coliforms and bioactive phosphorus forms in field studies. The experimental results added critical information about the relative potential impacts of farming practice and the mitigation of the impacts of manure applications on near-by aquatic environments. This is particularly important to small organic farms employing animal manure as primary source of organically based plant nutrients. Information of manure-borne contaminant transport is critically needed by USEPA and state regulatory agencies in assessing risks and in the design of preventive practices and structures such as vegetative buffers and riparian zones in the containment of manure-borne bacteria and phosphorus.

ARS scientist made an invited presentation at the Sustainable Nutrient Management in China Workshop to describe the technological options available to manage phosphorus and nitrogen in corn production systems. Selected on-farm quick tests for soil and fertilizer and organic inputs, biosensors for the detection of nutrient status, and plant tissue analysis were examined. It was stressed that activities of phosphatases, as well as a whole suite of soil enzymes, are important indicators of soil fertility, nutrient bioavailability, and overall system health. These approaches can be applied to improve nutrient use efficiency to attain long-term sustainability and reduced potential impairment of the environment by production agriculture.

The REM Engineering Co. in agreement with Allen Family Foods planned to build a steam generation facility fueled by poultry litter and use the ash as a fertilizer for agricultural crops. Contacted by local farmers who were planning to use poultry litter ash, ARS scientist plans an evaluation of the ash as a fertilizer for corn production.

6.Technology Transfer

Number of Non-Peer Reviewed Presentations and Proceedings2

Review Publications
Dao, T.H., Zhang, H. 2007. Rapid composition and source screening of heterogeneous poultry litter by energy dispersive x-ray fluorescence spectrometry. Annals of Environmental Science. 1:69-79.

Green, V.S., Dao, T.H., Stone Jr, G.N., Cavigelli, M.A., Baumhardt, R.L., Devine, T.E. 2007. Bioactive Phosphorus Loss in Simulated Runoff From a P-Enriched Soil Under Two Forage Management Systems. Soil Science. 172:721-732.

Dao, T.H. 2008. Review of Modeling Phosphorus in the Environment. Soil Science Society of America Journal. 72(2):278.

Dao, T.H., Hoang, K.Q. 2008. Dephosphorylation and Quantification of Organic Phosphorus in Poultry Litter by Purified Phytic-Acid High Affinity Aspergillus Phosphohydrolases. Chemosphere. 72:1782-1787. (

Last Modified: 3/29/2015
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