The effect of conventional cultivation, direct drilling and crop residues on soil temperatures during the early growth of wheat at Murrumbateman, New South Wales

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Abstract
Soil temperatures were measured at different depths under wheat crops sown by three different methods in a dry (1982) and a wet season (1983). A conventionally cultivated treatment, which comprised a short cultivated fallow, was compared with one which was directly drilled with full disturbance of the soil surface after previous crop residues had been burned, and with another treatment which was directly drilled with minimum disturbance into soil carrying 2-4 t ha-' stubble. Generally the soil temperatures at any particular depth of the conventionally cultivated treatment were warmer during the day and cooler during the night than the soil temperatures at the same depth in the direct drilled treatments. These patterns persisted throughout both the growing seasons, but in the wet year (1983) there was little difference between temperatures under conventional cultivation and direct drill with stubble burning and full disturbance. Similar temperature patterns were measured when the same treatments were imposed on an adjacent area which had previously been growing fertilized ryegrass/clover pasture. It was found that wheat sown by conventional means had a larger shoot dry weight per plant at the 4 1/2 leaf stage of development than direct drilled wheat. The improved early vigour of wheat sown by conventional cultivation practices could at least partially have been due to the patterns in soil temperature.
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