Related Topics

1a.Objectives (from AD-416):
1. Develop practices to enhance the beneficial use of manure nutrients and reduce offsite losses through management of the environmental fate and transport of organic carbon, nitrogen, and phosphorus derived from poultry, dairy, and beef cattle manures. 2. Develop integrated crop, soil, and dairy/beef/poultry manure management strategies to improve nutrient utilization and minimize leaching and runoff losses.

1b.Approach (from AD-416):
Real-time tools for rapid C, N, and P detection and multi-element analysis of manures, soils, and crops will be evaluated and adapted to develop precision nutrient management practices under changing soil microenvironment and weather conditions. Process knowledge affecting C, N, and P transformations and detection will be gained to establish databases and develop algorithms to assist in the management of bionutrient mineralization and availability in conservation cropping systems.

3.Progress Report:
Nutrients used in production agriculture, particularly manure nutrients, continue to cause the degradation of natural ecosystems. Overestimating phosphorus needs of crops contributed to large surpluses in soil for the last 18 years of a study of conventional and organic farming systems. Current soil testing procedures do not account for the presence and size of the organic phosphorus fraction in organic amendments such as livestock manure or composts. An oversupply has long-lived impact and contributes to elevated phosphorus levels 12 or more years later, even after readjustment of rates of addition. Accurate estimates of crop requirements and soil phosphorus forms, and the development of on-the-spot plant and soil monitoring tools are critical to avoid oversupply and best utilize manure-derived nutrients in crop production in the mid-Atlantic region.

Cover crops can provide a valuable ecosystem service by conserving residual nitrogen after corn. The recovery of isotope-labeled fertilizer was used to directly compare the ability of rye, wheat, and native weeds to recover residual N applied to a preceding corn-silage crop. The field phase of this study has been completed, and samples are being analyzed for labeled N to follow changes in soil nitrate and the uptake of labeled N by the winter crops. The effectiveness of cover crop management strategies for capturing residual nitrate and thereby reducing nitrate losses to ground water and the Chesapeake Bay are being quantified.

4.Accomplishments
1. In long-term field studies, ARS scientists demonstrated a linkage between zones of phosphorus accumulation, manure composition, and soil biological properties for the last 18 years in no-till corn production. Applying manure at a replacement rate equal to that removed by crops did not prevent the accumulation of available and total phosphorus in these soils. Changes in the ratio of inorganic-to-organic forms, and their uneven distribution across the field during liquid manure spreading modified soil biological properties and risks of losses from treated fields. The variability in the ratio of phosphorus forms in the soil persisted over the years and the phenomenon distorts the picture of phosphorus availability in the field, and the formulation of phosphorus recommendations for future growing seasons. Customer/Users of this research include U.S. and international researchers, educators, NRCS, and Extension nutrient managers, consultants, organic farmers, and agricultural and environmental policy makers.

2. Nitrogen management strategies for no-till winter wheat in the mid-Atlantic. A four-year lysimeter study showed that during the fall establishment season, no-tillage produced significantly higher drainage volumes and nitrate leaching losses compared to plow-tillage. Limiting fall-N applications and timing spring-N applications to coincide with wheat N demand were shown to be good management practices for reducing nitrate leaching losses. Customer/Users include researchers and educators, NRCS and Extension nutrient managers, state environmental staffers, and private industry fertilizer and nutrition managers.

Review Publications
Dao, T.H., Schomberg, H.H., Cavigelli, M.A. 2014. Tillage and rotational effects on exchangeable and enzyme-labile phosphorus forms in conventional and organic cropping systems. Nutrient Cycling in Agroecosystems. 101:153-165.