Evaluation of nitrate-nitrogen transport in a potato-barley rotation

Well water NO3--N concentrations have been found to exceed 10 mg L-1 of NO3--N for some areas of the San Luis Valley (SLV) of South-Central Colorado. The region's predominant soils are sandy soils, with a dominant potato (Solanum tuberosum L.) followed by malting barley (Honieum vulgare L.) crop rotation. There is limited knowledge about how much NO3--N is lost by leaching from these systems, and protocols need to be developed to evaluate the NO3--N transport out of these coarse textured soils from these arid and semiarid irrigated cropping systems. Management information, N content at harvest, initial and final NO3--N in the soil profile, and other supportive data were collected at 14 commercial fields and used as inputs for the Nitrate Leaching and Economic Analysis Package (NLEAP) model, version 1.20. NLEAP simulated available soil water for the root zone as well as the transport of NO3--N in the soil profile, and can be used as part of the protocol to evaluate the NO3--N transport of these systems. Best recommended practices in this region, such as application of N fertilizer rates on the basis of soil test analysis and split applications of N fertilizers, kept the net transport of NO3--N out of the potato-barley systems to a minimum. Our approach of applying simulation models to assess management scenarios showed that barley served as a scavenger for the NO3--N that was added with irrigation water and the residual soil nitrate from the potato growing period.