Field Evaluation of Soil Acidity Acidity Effects on the Growth of Annual and Perennial Ryegrasses

Soil acidity limits pasture establishment and productivity in the moister eastern half of South Africa. Sound lime requirement guidelines based on soil test data are required. In the study reported here, lime responses of annual (Lolium multiflorum) and perennial (Lolium perenne) ryegrasses were evaluated in irrigated field trials located on acidic, highly weathered soils. Annual ryegrass (yield response to lime 27 to 32%) was found to be markedly more tolerant of soil acidity than perennial ryegrass (yield response 68%). Acid saturations of up to 20% had little impact on the yield of annual ryegrass, while yield of perennial ryegrass declined sharply with increases in soil acid saturation above 0%. Annual ryegrass was more sensitive to acidity during the establishment phase of growth leading up to the first harvest, relative to growth during the remainder of the season.