Net returns from terrain-based variable-rate nitrogen management on dryland spring wheat in Northern Montana

Abstract

Agricultural producers can use variable-rate application technology to vary N fertilizer within fields. ­ is study was conducted toestimate changes in net returns from implementation of variable-rate N management (VNM) on hard red spring wheat (Triticumaestivum L.) in a summer-fallow region in northern Montana. Net return from uniform N management (UNM) traditionallyused by producers was compared with that from VNM in eight dryland fields between 1994 and 2004. Field experiments consistedof a replicated series of four to six N rates applied within strips oriented with the length of each field. Management zones (MZs)were created by dividing the fields into upper slopes, south-facing middle slopes, north-facing middle slopes, and lower slopes.Nitrogen recommendations for MZs were based on soil N testing and expected yields. Grain yield data were obtained using aproduction-size combine equipped with a yield monitor. Mean grain protein and yield were similar between VNM and UNM.Yield di erences were <223 kg ha –1 and averaged only 18 kg ha –1. Grain yield did not di er significantly among N rates within MZs. In seven of the eight sites, net returns from VNM were up to US$27.97 ha –1 less than from UNM and were not profitableif Environmental uality Incentive Program payments of US$6.36 ha –1 were considered as part of net income. Little evidenceexisted that VNM based on constructed MZs and predetermined N recommendations improves grain yields and profits orreduces N use in water-limited, summer-fallow systems of northern Montana.