Compost Bedded Pack Dairy Barn Nutrient Characteristics.

Because of increased regulatory pressure to control non-point source pollution of nitrogen and phosphorus, dairy farmers are developing more sophisticated nutrient management approaches. Farmers are subject to a phosphorus index in determining application rates of agricultural waste.  Regional native soils exhibit high levels of phosphorus mineralogy and little is known about the effects of waste inputs on soil phosphorus dynamics.  Compost Bedded Pack Dairy Barns (CPBD) are a relatively new housing and nutrient management strategy.  It is believed that CBPD barns are a potentially more sustainable nutrient management approach.  The dairy wastes are converted, in situ, into a stabilized soil amendment that can supplement the use of inorganic fertilizer in crop production. Little is known about the nutrient release characteristics of the CBPD barn material and how it compares to that of typical manure amendments. The objective of the study was to determine the effect of CPBD and other waste amendments on phosphorus transformations in native soils.  To develop an understanding of the behavior of the material with time in relation to decomposition and nutrient release characteristics, a litter bag study was performed. An aerobic mineralization study was performed to discern the phosphorus dynamics of soils amended with raw dairy manure and CBPD barn material as well as the nutrient release characteristics thereof.  Preliminary studies revealed that approximately 40 to 60 percent of the nutrients of compost material were available, which differs from values suggested by regulatory agencies for typical animal wastes and much less than raw dairy manure, which is estimated to be upwards of 90 percent available in a growing season. The increased adoption of the CPBD system and expanding organic agriculture fertility market necessitates characterization.  From these studies, we hope to provide guidance in aiding land managers, nutrient management planners, and regulatory agencies in mitigating the risk of phosphorus loading to soils and subsequently ground water.