Importance of rainfall oscillations in agricultural planning

Abstract

Evidence seems to indicate that the rainfall in the summer rainfall area of the RSA exhibits an oscillatory nature with a period of 16–20 years. To help maize farmers in planning for a dry or wet cycle the most recent dry (1963–1972) and wet (1973–1981) half-cycles were studied. Results showed that planting dates are not affected significantly. On soils with a high water-holding capacity, target yields should not differ by more than 10% at Potchefstroom, Bethlehem and Cedara. On soils with low moisture-holding capacity, however, the target yields could vary markedly between wet and dry half-cycles and in marginal rainfall areas (e.g. Glen) the risk of failure is high. It is imperative to take both climate and soil factors into consideration to ascertain the risk associated with dryland cropping.