The University of Delaware currently maintains two "long-term" (22-year) field sites in Georgetown, Delaware and Chestertown, Maryland. The study provides information that allows University of Delaware researchers to better understand the behavior of phosphorus (P) in soils receiving long-term P applications. Rotational P balances and soil test P rate of change estimate in soils managed under different manure and fertilizer treatments over the 22-year study period will be summarized at the end of 2022. This information will help the University to make better manure and fertilizer management recommendations for crops on the Delmarva.
Preliminary results are showing that applications of poultry litter or commercial fertilizers at rates that are below crop removal will result in an overall decline in soil test P, even if these P sources are applied to "High" P soils. In some cases, applications at P removal rates can also result in overall declines in soil test P. Data from this study will guide P management for fields with no or minimal manure history that may received manure transported from areas with "High" P soils, allowing farmers to benefit from the organic matter and nutrients in poultry litter without building soil test P to levels that cause environmental concern.
University of Delaware researchers will also submit the data set for inclusion in a new national soil testing database called Fertilizer Recommendation Support Tool (FRST), FRST will be a searchable web-based tool that provides more consistent, transparent, and science-based decision support nutrient recommendations across the USA for major crops, including but not limited to corn, grain sorghum, peanuts, soybeans, and wheat.