SOIL TEMPERATURE UNDER ZERO TILLAGE SYSTEMS FOR WHEAT IN SASKATCHEWAN

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Abstract
Soil temperature profiles and the aerial growth of wheat were characterized over portions of the growing season in 1980 and 1981 under zero and conventional tillage systems in a semi-arid region of Saskatchewan. Differences in maximum and minimum soil temperature, accumulative heat sums and thermal diffusivity over the 2.5-cm to 20-cm soil depth were related to variations in surface crop residues, soil moisture and crop canopy. Generally, maximum soil temperatures were 1–5 °C lower under zero tillage compared to conventional tillage during the first 30 days of crop growth for spring wheat. Similar soil temperature differences were evident between winter wheat zero tilled on stubble or chemical fallow during the period of early spring growth. Subsequent differences in crop canopy (shoot height), between tillage systems, tended to modify the soil temperature profile. Soil temperature differences were not associated with differences in yields of spring or winter wheat. Key words: Soil temperature, soil thermal properties, zero tillage systems, wheat,semi-arid climate