EFFECT OF GROUNDWATER LEVEL DEPTH AND IRRIGATION AMOUNT ON WATER FLUXES AT THE GROUNDWATER TABLE AND WATER USE OF WHEAT

Three irrigation water regimes (90.0, 67.5, and 45.0 mm) and five groundwater table depths (1.5, 2.0, 2.5, 3.0, and 3.5 m) were considered in a lysimeter experiment to investigate the effect of groundwater level and irrigation amount on water fluxes at the groundwater table and water use of wheat. Results show that deep percolation (irrigation of 16-23%) occurred to a considerable extent in the present irrigation level at a shallow groundwater table of 1.5-2.0 m. Capillary rise comprised 29% of the water use of wheat, within the period from regreening to harvest, at 1.5 m groundwater table depth, and was reduced with an increase in table depth. A relationship between groundwater contribution and groundwater table depth was also found. In the present irrigation conditions, the water productivity (WPb) of wheat was enhanced from 3.59 kg m(-3) at a shallower groundwater level depth of 1.5 m, to 4.58 kg m(-3) at a deeper groundwater level depth of 3.5 m. WPb can be higher if deficit irrigation is enforced and can reach 3.93-6.03 kg m(-3). Similarly, a relationship between WPb and groundwater table depth was found. Hence, the irrigation amount per time for local wheat can be reduced to 45.0-67.5 mm, depending on the groundwater level depth, in order to use water resources effectively. Copyright (c) 2011 John Wiley & Sons, Ltd.