Lime-phosphorus interactions in the growth of temperate pasture species on highly-weathered soils

Abstract

Lime and phosphorus (P) requirements for the growth of temperate pasture species on acid, well-drained soils in the Natal Midlands were evaluated in factorial field trials. Species studied were white clover (Trifolium repens), tall fescue (Festuca arundinacea) and Italian ryegrass (Lolium multiflorum). All three species exhibited large yield responses to lime and P. In addition, evidence for both positive and negative lime-P interactions was present in dry matter production data. Positive interactions, exhibited during the establishment phase of growth of white clover and Italian ryegrass, appeared to be restricted to conditions of severe P deficiency. Yield data of all species contained evidence of negative interactions, which occurred at more favourable levels of P supply. Negative interactions reflect a decrease in response to P with increasing lime supply (to salt pH values of approximately 5.5). The latter interactions are of major importance from a practical standpoint since they imply a ‘trade-off’...