Tillage Effects on Soil Temperature, Soil Water, and Wheat Growth in South Australia

Plots of an Urrbrae fine sandy loam (Rhodoxeralf) were tilled with either a scarifier (tine digger) or a rotary cultivator (rotovator), or left untilled as checks. Wheat ( Triticum aestivum L. cv. Gabo) was planted 9 June 1981 on half of the tilled plots resulting in five treatments randomized over plots in each of three replicates. Soil temperatures at the 50‐mm depth and microclimate variables were measured every half hour in one replicate only. Soil water content in the surface 10 mm was measured at 0800 and 1600 h on work days in two replicates. Soil water profiles, plant heights, soil structure, and penetrometer resistances were determined at various times on selected plots and replicates during the growing season. June and July were unusually cool and wet and wheat growth was slow. After 12 August, wheat grown on rotovated plots was significantly taller and yielded more at harvest in December than wheat grown on scarified plots. Soil temperatures at 50 mm differed only slightly among treatments except for wheat vs. no‐crop where the wheat plots had lower daytime soil temperatures after 8 September. Soil water in the surface 10 mm tended to be greater for scarified treatments than for rotovated treatments until late August. It was concluded that differences in wheat plant height were related to soil structure and soil water but not to soil temperature.