Effect of deep tillage and seedbed preparation on the growth and yield of wheat on a hard-setting soil

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Abstract
The preparation of a seedbed using either conventional cultivation (3 scarifyings) or deep tillage increased the vegetative and grain yield of a wheat crop (cv. Banks in 1983, and Quarrion in 1984) when compared with the direct drill technique of crop establishment on a hard-setting red duplex soil (Dr 2.62). Neither vegetative nor grain yield was increased by the inclusion of a deep tillage operation on the conventionally cultivated treatment prior to seedbed preparation with a scarifier. The poor seedling vigour of direct drilled plots was eliminated by deep tillage. However, the effect of deep tillage was short-lived. The importance of good soil physical condition during crop establishment was highlighted by the recompaction of the cultivated soil to bulk density and shear strength levels similar to those of the uncultivated plots in the latter part of the growing season. Because of the fragile nature of the soil, there were no residual benefits from the deep tillage operation on the undisturbed plots in the following season. Although cultivation had obvious benefits in enhancing seedling vigour on the hard-setting soil, the destruction of the soil's macroporosity reduced water infiltration down the soil profile. The adoption of conservation farming practices on hard-setting soils should initially involve reduced cultivation techniques to promote early seedling vigour. This cultivation should be timed to minimise the risks of soil erosion and recompaction. Further work is needed to identify the optimal cultivation techniques for these soils.