Optimizing irrigation management for wheat to reduce groundwater depletion in the piedmont region of the Taihang Mountains in the North China Plain

Sustainable water use in the piedmont region of the Taihang Mountains in the northern part of the North China Plain (NCP) is under serious crisis due to the rapid depletion of groundwater caused mainly by pumping for agricultural irrigation. The development of water-conserving agricultural practices is essential in order to limit agricultural water use. To find an effective way to save water in the wheat-growing season without markedly reducing wheat yield, DSSAT-wheat was calibrated, validated and used to simulate water use by winter wheat. The simulations suggest: (1) since a moderately low growth in the leaf area index (LAI) of wheat does not result in low yield, moderate water deficits in March can save water, and therefore, the aim should be to avoid irrigation in March. (2) Depending on the soil water condition, irrigation in mid November is recommended to obtain a good growth of LAI and to create a moderate condition for water stress in March. (3) After the start of the growth of the ears (around 15 April), water deficits should be avoided so as to ensure there is no influence on ear growth and grain filling. Simulation of a 12-year period showed that when irrigation practice follows the above three principles, 76 mm of evapotranspiration and 99.5 mm irrigation water can be saved without much reduction in the yield of winter wheat (only 4.5%). This is sufficient to decrease the drawdown of groundwater by 0.42 m a(-1) and to improve water use efficiency from 1.27 to 1.45 kg m(-3). (c) 2005 Elsevier B.V. All rights reserved.