Shallow groundwater enhances water productivity of maize in arid area

Agricultural water saving measures play an important role to manage water shortages and agricultural production in arid and semiarid areas. In areas with shallow groundwater, capillary upflow from the groundwater is important for crops to receive adequate water under limited irrigation. To understand the effect of limited irrigation and groundwater on crop water use, a calibrated AquaCrop model with 2 years of field experimental data was used to simulate the increase in groundwater capillary in different depths of groundwater and amounts of irrigation amount. The results showed that the following: (1) Plant transpiration and actual evapotranspiration reached their maximum at a groundwater depth of 1.5 m and decreased as the levels of groundwater decreased. Plant transpiration and actual evapotranspiration remained almost unchanged when the groundwater depth was > 2.5 m. (2) The capillary rise gradually decreased as the groundwater depth increased. When the groundwater depth was at 1 m, the capillary rise could reach 224.3 mm, and the capillary rise in seedling stage accounted for 61.9% of the whole growth period. (3) When the groundwater depth varied from 1.5 to 2.5 m, both the water productivity and irrigation water productivity of maize were maintained at a high level. Since the adjustment of maize yield should not be lower than the local average level, the appropriate irrigation amount should be 279 mm, and irrigation should be conducted during the key growth periods of maize (jointing, tasseling and filling stages). These results should be useful to improve irrigation management considering the groundwater depth distribution for the sustainable development of the semiarid and arid regions and alleviate the shortage of water resources.