Lime and phosphorus effects on the dry matter production of eragrostis curvula on dystrophic clay soils

Abstract

The dry matter yield responses of Eragrostis curvula to P and lime over two seasons on Balmoral and Balgowan soil series in the Natal Mistbelt are discussed. With this work forming part of a study aimed at characterizing P fixation in these soils, P (0, 100, 300 and 600 kg P/ha) and lime (0, 2 000 and 6 000 kg/ha as calcium hydroxide), were applied three years prior to establishment of E. curvula. Highly significant yield responses to P were noted, P effects being particularly dramatic at establishment, when response continued to the highest P level. Yields over the two seasons were closely related to soil test (AMBIC) values, with a threshold P test of 7mg/L being indicated. E. curvula displayed a remarkable ability to tolerate soil acidity, and yield responses to lime, although significant, were not nearly as marked as responses to P. In the absence of lime, where acidity was severe (pH[KCl] = 3,8 to 3,9; soil acid saturation = 60 to 80 %) yields were 87 to 97 % of those attained with the highest lime level.