Plant Nutrient Flow in the Managed Pathways of an Intensive Dairy Farm

Abstract The magnitude, and spatial and temporal patterns of nutrient flow in the managed pathways of a farm are related to farm management decisions and interact with the biological processes of the farm. These descriptions of nutrient flow can be part of a nutrient management process that is consistent with the specifics of individual farm operations and particular farm performance goals. Nutrient flow in the managed pathways of a Pennsylvania dairy farm was measured at farm, field, and livestock unit boundaries using on‐farm equipment scales, farm records, and material sampling and analysis. Farm nutrient inputs of N, P, and K were twofold or more greater than outputs of these nutrients in the managed pathways. The temporal distribution of flows was closely related to the livestock activities on the farm. Manure storage capacity and crop developmental stage were significant factors influencing the timing of nutrient flows to and from the fields. Nutrient inputs and outputs in the managed flows at the boundary for the set of all fields were approximately equal except for the negative calculated crop available N balance. However, the range in balances for individual fields was large. Manure N and potential biological N fixation were not used efficiently on this farm due primarily to the volatilization of N from manure and the application of manure to alfalfa. Additions of nutrients to the farm in the managed flows decreased by 26, 60, and 43% for N, P, and K, respectively, in the 2nd yr of the study due primarily to less purchased animal feeds.