| Popis: |
High yielding irrigated hard red winter wheat (HRW, Triticum aestivum L.) is frequently low in protein and marketed at a discount. Protein is affected by available nitrogen (N) but few published reports relate to N fertilization practices for producing high yielding irrigated hard red winter wheat with acceptable protein in arid environments. A three year study (1985–1987) was conducted (1) to determine the influence on irrigated HRW yield and protein of fall preplant, spring topdress, and late N applied, and (2) to evaluate flag leaf nitrogen concentrations (FLN) for scheduling late season N. Early season N treatments for vegetative growth consisted of an untreated control (0 N), and 168 kg urea N ha−1 either broadcast preplant and incorporated in the fall, topdressed in early spring, or both (336 kg N ha−1 total). Applying late season N at heading or flowering (0 or 56 kg urea N ha−1) was evaluated with all earlier season N treatments. The N applied for vegetative growth increased yield from 3.6 to 4.1 Mg ha−1 and protein from 15 to 47 g kg−1. The timing of N application (fall versus spring), without late season N, did not affect grain yield but protein was 8–13 g kg−1 higher with spring topdressed N. Excessive N (336 kg N ha−1) during vegetative growth consistently reduced grain yield of non-lodged wheat due to lighter kernels. Protein increases with late season N were highly dependent on the earlier season N rate and timing. Late season N was essential for increasing protein to 120 g kg−1 without incurring yield losses from excessive N during vegetative growth. FLN was directly related to protein, and inversely related to the late season N induced protein increase. However, the protein relationships to FLN differed markedly among years. Normalized FLN values, dividing all values for a year by the highest value in that year, greatly reduced the year effects. Both high yields and acceptable protein of irrigated HRW are possible with sufficient N during vegetative growth for yield and late season N for protein enhancement. |
Full Text from ScienceDirect