Measuring extractable soil phosphorus increase from dairy cow manure applications

Dairy farmers in Connecticut often use dairy cow manure to fertilize silage corn fields that feed cows. Although corn crops extract nutrients applied to these fields, phosphorus (P) is often accumulating in fields faster than it is extracted. One reason this occurs is because of uneven distribution of manure across cornfields due to financially inefficient transportation costs. Because farmers may soon be prohibited from applying P from any source to fields with extractable P concentrations greater than the environmental critical concentration, they are becoming increasingly concerned about P accumulation in cropland. Farmers are also concerned about exceeding the environmental critical concentration of P in fields still receiving manure. We have designed a project to estimate the rate of increase in extractable soil P after dairy manure applications on typical silage corn fields in Connecticut and how much soil P moves through the upper soil profile. We intend to address the nutrient management priority of NRCS-CT. Specifically, the issue of P accumulating in silage corn fields receiving dairy cow manure. We believe this information will have a positive influence on the ability for dairy farmers to create long-term nutrient management plans to balance environmental and economic sustainability.