Uptake and utilisation of phosphorus and nitrogen by bread wheats grown under natural rainfall

Abstract

Wheat genotypes were grown in a Mediterranean environment in 3 seasons with 3 levels of applied phosphorus (P) and nitrogen (N) fertilisers. Phosphorus and N concentrations were measured in mature grain and straw. The amounts and distributions of these nutrients were calculated and differences between genotypes were related to plant yield components. Harvest index was more highly positively correlated, than grain yield, with nutrient harvest index and yield per unit of shoot P, but more negatively correlated with grain nutrient concentrations. For each percentage point increase in harvest index, grain protein declined by 0.08 percentage points and grain phosphorus by 0.0015 percentage points.It is suggested that improved utilisation of phosphorus by wheat is possible through increases in harvest index and by direct selection of genotypes with similar harvest index. Examples are given to show that selection for low grain P can proceed in association with selection for high grain protein