Kidney bean (Phaseolus vulgaris L.) production on an irrigated, coarse-textured soil in response to polymer coated urea and tillage: II. Plant N accumulation, nitrate leaching and residual inorganic soil N

Abstract

Kidney bean (Phaseolus vulgaris L.) production in Minnesota is inherently at risk for nitrate (NO3) leaching since the crop is typically grown on irrigated coarse-textured soils. These soils contain a dense Bt layer, which growers feel must be broken up through deep plowing to reduce severity of root rot. This study was conducted to determine the effects of polymer coated urea (PCU, Agrium U.S. Inc. and WSPCU, Specialty Fertilizer Products) and tillage depth on water percolation, nitrate leaching, and plant nitrogen (N) uptake. In a split plot design, deep and shallow tillage (plow depths of 47 and 29 cm, respectively) were whole plots while N treatments were subplots. Three rates of emergence applied PCU were compared with equivalent rates of urea split applied at emergence and prebloom. Along with a 0 N control, additional treatments included one rate of each N source, including WSPCU, applied at planting. Differences between tillage treatments were not found except as interactions with N treatment. In dry years, emergence applied PCU resulted in reduced grain N uptake and more cumulative NO3 leaching than split applied urea. In a wet year, however, emergence applied PCU resulted in similar plant N uptake and significantly less NO3 leaching that split applied urea. Planting applied PCU resulted in similar plant N uptake and generally less NO3 leaching compared with split applied and planting urea, regardless of leaching conditions. In dry years, planting applied WSPCU resulted in similar grain N uptake and NO3 leaching as planting applied urea and PCU.