Environmental causes of yield variation in raingrown sunflower in Central Queensland

Abstract

A three year trial series at Biloela Research Station, Central Queensland, was initiated in 1972 to provide information on the environmental causes of sunflower yield variation in this region. The crop daily water use was estimated by running a simple empirical water budget between actual gravimetric soil water determinations. This budget indicated that a better crop water status, at anthesis, could be produced by a slightly quicker cultivar development pattern than that of the current cultivars. The observed yield variation was found to be more highly correlated with an index of the average crop water status in the 30 days surrounding the appearance of the first anther, than by a multiple regression of the individual environmental factors involved. The best explanation of the yield variation (R2 = 96.7 per cent) was given by: Yield = 2034.2 + 241.7 L.A.I. - 309.4 loge Stress Index - 55.4 Rust Index. This paper presents the data on which this relationship was based and looks at its potential merits and defects as a tool for analysing past meteorological records to formulate yield frequency diagrams for this region