Nitrogen uptake across site specific management zones in irrigated corn production systems

Development of improved fertilizer management practices has the potential to increase fertilizer use efficiency and improve environmental quality. The objectives of this study were (i) to characterize the within field spatial variability of N uptake across irrigated corn production fields, (ii) to quantify and compare N uptake and grain yield across three site specific management zones (SSMZs), and (iii) to compare grain yield response to applied N between management zones. This study was conducted on continuous corn (Zea mays L.) in irrigated fields in northeastern Colorado. Fields were classified into high, medium, and low site specific management zones. Treatments consisted of a control and two uniform N application rates over 2 site-years (one field over 2 consecutive yr and another field over 1 yr). Nitrogen fertilizer rates varied with site-year and ranged from 56 to 268 kg N ha(-1). Aboveground biomass samples were collected at physiological maturity and analyzed for total N. Between management zones, N uptake, grain yield, and grain yield response to applied N were found to be statistically different (p < 0.05). Management zones were found to be less spatially variable than the whole field. The SSMZs accurately characterized variability in N uptake as well as grain yield response to applied N. Thus, variation in N uptake and grain yield can potentially be managed using SSMZs.