The effect of fallowing on the yield of wheat. II. The effect on grain yield

Abstract

The effect of fallowing on wheat yields is reported for a South Australian environment where 62% of the variation in yield is ascribed to water supply and where water use efficiency in grain production ranges from 1 to 11 kg/ha/mm. The mean yield response from a fallow (initial tillage 9 months before sowing) compared with a non-fallow (tillage 2 months before sowing) in 28 seasonal, site and fertility situations was 335 kg/ha and the maximum 875 kg/ha. Each additional millimetre of water stored through fallowing gave on average 8 kg grain per ha. Only fine-textured soils stored considerable water through fallowing. The additional nitrate in fallow gave yield responses when the non-fallow soil contained less than 70 kg nitrate nitrogen per ha, but only when water use by the crop exceeded 230 mm. The results are related to responses to fallowing obtained in other wheat-growing districts in Australia.