DYNAMICS OF DRY MATTER, N AND P ACCUMULATION IN THE DEVELOPING KERNELS OF FOUR SPRING WHEAT CULTIVARS FOR IRRIGATION AND DRYLAND
The effect of moisture and cultivar on the dynamics of N and P concentration and on dry matter, N and P accumulation of the developing central kernels on the main spike of four wheat (Triticum spp.) cultivars were determined. Two common wheat (T. aestivum L.) cultivars, Neepawa and HY320, and two durum (T. turgidum L. var. durum) cultivars, DT367 and Wakooma, were grown on an Orthic Brown Chernozem in southwestern Saskatchewan in 1985. HY320 and DT367 have higher grain yield potentials and lower protein concentrations than Neepawa and Wakooma. Logistic equations satisfactorily decribed the accumulation patterns of dry matter, N, and P contents in the kernels from anthesis to maturity, while linear and second degree polynomials adequately described the variations in N and P concentrations. Response of N and P concentration to moisture and cultivar was variable but could be explained in terms of rate and amount of dry matter accumulation in kernels and the greater mobility and availability of N compared to P in soil. N and P accumulation was mainly dependent on kernel dry matter response, although N and P concentration did influence accumulation patterns under irrigation. Duration of accumulation of dry matter, N and P in kernels were equal under dryland, but under irrigation the period was several days longer for N than for dry matter and P. Cultivar had no effect on duration of N accumulation under irrigation, but on dryland duration was shortest for Neepawa. For P accumulation, duration was longest for HY320. The mean rates of accumulation of kernel dry matter, N, and P were directly related (R2 = 0.98**) to kernel dry matter, N, and P content, respectively.Key words: Wheat, Triticum aestivum L., Triticum turgidum L. var. durum, filling rate, filling duration