The pattern of nitrogen uptake in winter wheat

Non-Peer ReviewedThe pattern of nitrogen uptake was examined in Norstar winter wheat (Triticum aestivum L.) grown at several locations in Saskatchewan during a three-year period. Replicated field trials were supplemented with 0, 34, 67,100, and, in the final year, 200 kg of nitrogen per hectare applied as ammonium nitrate (34-0-0) in the early spring. Plant samples were collected at two-week intervals during the growing season and analyzed for dry matter yield, nitrogen concentration and plant nitrogen yield. Modified harvest and nitrogen harvest indexes were calculated by comparing the wheat heads to the total plant material. In general, nitrogen concentration of stems and leaves decreased during the growing season while changes in nitrogen concentration of the wheat heads were more dependent: on environmental conditions. Dry matter yield and plant nitrogen yield increased during the season. This increase tended to level off near maturity at some locations, especially when moisture conditions were low. When soil nitrogen levels were low, increased amounts of nitrogen fertilizer increased dry matter yield and yield of plant nitrogen per hectare but had no effect on plant nitrogen concentration. When soil nitrogen levels were high and soil moisture was adequate, addition of nitrogen fertilizer increased only plant nitrogen concentration. At some locations, plant stand variability was too large to detect differences among fertilizer treatments. At most locations there were no differences among the fertilizer rates for harvest and nitrogen harvest indexes, indicating that there was no change in plant efficiency with a change in available nitrogen