The Influence of Rainfall on the Yield of Wheat in South Australia

Abstract

The relationship between the yield of wheat and seasonal rainfall inSouth Australia has been determined. The period chosen for examination was1896-1941 and the analysis extends to practically the entire wheat belt of theState, all major soil groups and variants of climatic conditions within the areabeing represented. Yield was assessed using the hundred, which has anaverage area of approximately 118 square miles, as the basic territorial unit.Seasonal weather was represented by the rains in three subdivisions of thegrowing period of the crop, and these were taken as independent variates inan analysis by multiple regression. The regression of yield on rainfall, whenconsidered as a,function of time, takes a mathematically simple parabolic formwith a maximum in winter and zeros in autumn and spring or early summer,and the coefficients obtained provide a clear demonstration of the sub-optimalcharacter of average seasonal rainfall over the greater part of the season andalmost throughout the wheat belt. The conclusions drawn from the generalsurvey are substantiated by analyses of a limited number of exact records.