The effect of drought on the root growth of winter wheat and on its water uptake from a deep loam

Abstract

Abstract. Avalon winter wheat was grown on deep silty clay loam soil (Hook series) under a fixed shelter at Rothamsted with either full drought or irrigation from the end of March to July, 1982. During this time the irrigated crop used 295 mm of irrigation water plus 45 mm of stored soil water, while the droughted crop extracted 223 mm of water from the soil. The roots penetrated to at least 1.8m and water was extracted from 2 m depth.Even with a fully developed root system the crops could transpire at the full rate of atmospheric demand only when the near‐surface soil was well supplied with water. However, the draughted crop extracted enough water from the loamy sub‐soil to maintain a reduced transpiration flow for a further nine weeks after the near‐surface water was depleted. Thus crop growth was maintained with a loss at final harvest of only 10% in total dry weight and even less in grain yield.A summary of other results confirm that yield losses due to drought have been reported only for light soils, except in the exceptional year of 1976, and that drought is not normally an important factor affecting yields of winter wheat in the UK.