Nitrogen Stress of Winter Wheat Changed the Determinants of Yield and the Distribution of Nitrogen and Total Dry Matter During Grain Filling

Abstract

The yields of grain dry matter (DM) and nitrogen (N) of winter wheat (cv. Maris Huntsman) were decreased by 26% and 45% when no fertilizer-N was applied in the spring. Fewer ears per m² and less mass of N per grain were the major reasons for the decreased yields. The low-N treatment decreased the rate and duration of grain filling for N but not for DM. Net assimilation of DM and N by the shoots of the low-N crop ceased at 35 and 28 days after anthesis but both continued, at a declining rate, through to maturity for the high-N crop; rates of grain-filling of DM and N were sustained at a constant rate for 2 weeks more as vegetative DM and N were redistributed. From 28 days to maturity the potential contribution to grain yield of DM and N from mobilized sources was estimated at 65% for both for the high-N crop, and 96% and 87%, respectively, for the low-N crop.