NITROGEN AND PHOSPHORUS UPTAKE, TRANSLOCATION, AND UTILIZATION EFFICIENCY OF WHEAT IN RELATION TO ENVIRONMENT AND CULTIVAR YIELD AND PROTEIN LEVELS

A field study was carried out in four environments to determine the effects of available water and cultivar on N and P uptake, translocation, and utilization efficiency of wheat (Triticum spp.) cultivars with varying grain yield potential and protein concentration. Two common wheat (T. aestivum L.) cultivars, Neepawa and HY320, and two durum (T. turgidum L. var. durum) cultivars, DT367 and Wakooma, were studied. HY320 and DT367 had higher grain yield potentials and lower protein concentrations than Neepawa and Wakooma. Total plant N and P uptake was proportional to available water, and was strongly associated with dry matter accumulation. From 67 to 102% of plant N and 64–100% of P present at harvest had been accumulated by anthesis. Postanthesis uptake of N and P was greater under moist than under dry environments. There were few cultivar differences in uptake of N or P, and any differences observed were related to variations in plant dry matter. Nitrogen harvest index ranged from 71 to 85% and P harvest index ranged from 81 to 93%. Both indices responded to environment in the same way as grain harvest index; there were no cultivar differences for either N or P harvest index. From 59 to 79% of N and 75 to 87% of P present in vegetative tissues at anthesis was translocated to the grain; translocation did not vary among cultivars. The efficiency of utilization of N and P in production of harvest biomass and grain was directly proportional to water availability and was greater in the high yield cultivars HY320 and DT367 than in Neepawa and Wakooma. There was no evidence that selection for N uptake, translocation, or utilization efficiency would be useful in wheat breeding.Key words: Triticum aestivum L., T. turgidum L. var. durum, nitrogen harvest index, phosphorus harvest index