INFLUENCE OF NITROGEN-FERTILIZER ON GRAIN QUALITY IN WINTER-WHEAT

Between 1966 and 1969, 44 experiments on winter wheat tested 5 rates of N applied as spring top dressings of NH4NO3. At almost every site, increasing the rate of N applied decreased grain size and increased the N content of the grain. There was a marked effect of season: the sunniest season, 1969, produced the largest grain and the lowest mean N content; the season with the least soil moisture deficit, 1968, produced the highest mean N content. There was no relationship between N content and the variety of wheat or soil type. The N content of grain grown without N fertilizer was highly significantly related to reserves of available N in the soil, i.e., to the rate of fertilizer N required for maximum grain yield, determined by experiment. By using this relationship, the fertilizer N requirement at 20 sites with nil N plots was calculated and was found to compare favorably with the ADAS N Index prediction method based largely on previous cropping. Grain density was determined on 3 sites in 1967; with increasing rates of N, grain density increased slightly.