Responses of italian ryegrass to phosphorus on highly-weathered soils

Abstract

Italian ryegrass (JLoliwn multiflorum cv. Midmar) responses to fertilizer P were studied in field experiments under irrigation on highly-weathered ferrallitic soils at two localities in Natal. Each experiment was conducted over two seasons (1985 and 1986), the pasture being re-established after the first season. Large dry matter yield responses to P were measured on both soils. Phosphorus effects were greatest during the establishment phase (autumn) and, on the colder site, in spring. Concentrations of P in herbage were much lower in winter than in autumn or summer. The greater responsiveness to P in spring and the lower P concentrations in herbage during the colder months suggested that res..