Effect of phosphorus application on seasonal changes in nitrogen and phosphorus concentrations of four perennial Stylosanthes accessions

Abstract

Four perennial Stylosanthes accessions (S. hamata cv. Verano, S. scabra cv. Seca, cv. Fitzroy and CPI558 18) were grown for 4 years on a red earth soil in the semi-arid tropics with fertilizer phosphorus applications of 0 to 40 kglha. The concentrations of nitrogen (N) and phosphorus (P) in plant shoots were measured at monthly intervals from January to July in one season, with less intensive sampling in the other years. Some measurements were also made of N and P concentrations in litter. Phosphorus concentrations in shoot, leaf, stem and litter increased with increasing rate of application of P, but N concentrations in plant tissue were virtually independent of the rate of P application. The concentrations of both N and P in the shoots of all accessions declined during the growing season. Differences in nutrient concentrations between Verano and the S. scabra accessions were relatively small. Even without application of P, these legumes always had substantially higher concentrations of N and P than the native grass Heteropogon contortus, and could be expected to provide an improved diet for grazing animals.