Aboveground Nitrogen Accumulation as a Function of Time in Corn and Winter Wheat

Abstract

Midseason fertilizer nitrogen (N) rates based on predicted yields can be projected since both corn (Zea mays L.) and winter wheat (Triticum aestivum L.) can accumulate significant quantities of N early in the growing season. This study was conducted to establish the amount of N accumulated in corn and winter wheat over the entire growing season. Plots representing three N fertilization rates (0, 45, and 90 kg ha-1) and (0, 67, and 112 kg ha-1) were selected from two long-term wheat experiments located at research stations in Stillwater and Lahoma, OK, in 2006 and 2007. For corn, three N fertilization rates (0, 112 and 224 kg ha-1) and (0, 56 and 112 kg ha-1) were selected from N studies, located at Lake Carl Blackwell (LCB) and Perkins, OK, also in 2006 and 2007. Sequential biomass samples were collected from 1 m2 area clippings of wheat, and 1.5 m of row (0.76 cm spacing) for corn, throughout their respective growing seasons. Differences in total N uptake over the course of the growing season were strongly influenced by the environment. Thus, N uptake curves for either wheat or corn were noted to be unique by year and location. In general, this work showed that more than 45 percent of the maximum total N accumulated could be found in corn plants by growth stage V8. For winter wheat, more than 61 percent of the maximum total N accumulated at later stages of growth could be accounted for by Feekes growth stage 5. Our findings are consistent with those of others showing that yield potential can be predicted midseason since such a large percentage of the total N accumulated was accounted for early on in the growing cycle of both wheat and corn.