Soil water conservation under cultivated fallows in clay soils of south-western Queensland

Abstract

Three field experiments to study the effect of time and method of cultivation during fallow on soil moisture accretion and crop growth were established at a site near Charleville, Queensland. The soil was a grey-brown cracking clay (46 per cent clay) typical of the Mitchell grass (Astrebla spp.) downs. In the first experiment, soil moisture accretion was followed on plots cultivated in November 1966 with either a disc plough or scarifier or not cultivated. Soil moisture was increased in the 90 cm deep profile by cultivation, but remained almost constant for the duration of the summer fallow. There was no difference in soil moisture under the disced and scarified plots. The remaining experiments were designed to study the effect of cultivations during fallow on soil moisture at the time of sowings. One early summer cultivation resulted in soil moisture levels similar to that gained from two or more ploughings. However, crop yields were highest following three cultivations. It is concluded that two or three cultivations during fallow decreases loss of soil water through transpiration of weeds and should increase the number of years a forage crop can be expected in south western Queensland.