Assessment of the Integrated Farm System Model for Predicting Nitrate-Nitrogen Losses in Drainage Water from Manured Cropping Systems.

The Integrated Farm System Model (IFSM) is a process-based model that is widely used for whole-farm nutrient cycling and evaluating trade-offs among nutrient loss pathways. For dairy farms, nitrate-nitrogen (NO₃-N) leaching from manure-applied cropping systems can represent a substantial portion of the overall N-loss to the environment. However, the precision and accuracy of water drainage and NO₃-N leaching estimates from IFSM have not been assessed. Further, the model has not been applied to tile-drained systems. This study evaluates IFSM estimates of annual and event-based field drainage and NO₃-N losses in drainage from eight unique cropped sites that received liquid dairy manure. The validation dataset draws from a range of spatial scales, from small plot to whole-field; includes both free- and artificially-drained conditions; and represents a range of common dairy forage-cropping and management practices. Results will determine the degree of error associated with IFSM drainage and NO₃-N leaching estimates and indicate if IFSM can be used to simulate tile-drained systems. This information will assist in broader efforts to use IFSM simulations to optimize management strategies to reduce N-losses and improve N efficiency from US dairies.