EFFECTS OF BED WIDTH AND PLANTING DATE ON WATER PRODUCTIVITY OF WHEAT GROWN ON VERTISOLS IN THE ETHIOPIAN HIGHLANDS

Waterlogging is a challenge to wheat (Triticum durum Desf.) productivity under the rainfed system on Vertisols in the Ethiopian Highlands. However, using suitable seedbed types and manipulating planting dates can minimize the effects. A four-year (2000-2003) field experiment was conducted to evaluate three seedbed types, broad bed and furrows (BBF) with early planting, the traditional ridge and furrows (RF) and its modified version (wide ridge and furrows (WRF)), both under early and late planting, in terms of water productivity of wheat. The FAO AquaCrop model was used to estimate crop water requirements. The result indicated that late planting on WRF or RF significantly (p<0.05) increased grain yield and water productivity. Late planting on WRF (LWRF) increased rainfall water productivity by 66, 44 and 51%, respectively, as compared to BBF, early-planted WRF (EWRF) and late-planted RF (LRF). This was because of its increased effective area for crop growth over the RF and its relative suitability of planting time over the BBF. Therefore, late-planted WRF can be used for enhanced water productivity of wheat, while introducing fast-grow crops that are tolerant to waterlogging and growing early in the season may further enhance the land and water productivity in the area. Copyright (C) 2010 John Wiley & Sons, Ltd.