Effects of the irrigation quota and drip irrigation pipes spacing on growth and development of summer maize with subsurface drip irrigation

Water and soil resources in the North China Plain are mismatched. Traditional flood irrigation methods in this area have low water resource utilization and lead to serious water loss, which has caused a rapid decrease in groundwater levels. This study aims to improve the efficiency of irrigation water use in this area, determine the influence of subsurface drip irrigation on the field-scale water balance, and explore the effects of different irrigation amounts and drip irrigation zone spacing on the growth and water consumption of summer maize under subsurface drip irrigation conditions. Field experiments with two irrigation quotas (62 and 35 mm) and three drip irrigation pipes spacings (60, 80, and 100 cm) were conducted with the conventional flood irrigation as the control in farmlands in the North China Plain to analyze their effects on the growth and development, yield and irrigation water use efficiency of summer maize, and the soil profile moisture distribution, evapotranspiration, evaporation. Soil evaporation under subsurface drip irrigation was measured and compared using a microlysimeter. The results showed that irrigation water from subsurface drip irrigation mainly stayed in the 20–60 cm soil layer, and the wetted body presented a “small up and large down” form. The higher the irrigation amount, the larger the wetted body range, and the larger the soil volumetric water content. Compared to flood irrigation, the soil moisture contents of the 0–20 cm and 60–100 cm soil layers from subsurface drip irrigation were relatively low, and a dry soil layer formed at about 0–10 cm layer, which reduced soil evaporation. Maize plant height, leaf area index, and dry matter accumulation increased with increasing amounts of subsurface drip irrigation. Under flood irrigation, the maize plant height increased faster, and the accumulation rate of the maximum dry matter was higher compared to subsurface drip irrigation. Low amounts of subsurface drip irrigation delayed maize growth. When the irrigation amount was reduced by 22%, maize yield under subsurface drip irrigation did not differ from maize yield under traditional flood irrigation. Compared to flood irrigation, subsurface drip irrigation reduced soil evaporation by 30%, evapotranspiration by 8%, the E/ET value from 0.34 to 0.27; and increased the irrigation water use efficiency by 20%, the harvest index by 10%. The different drip irrigation zone spacing treatments had no effect on the growth and water consumption of maize. For high maize growth and yield, efficient irrigation water use, and cost-effective investments in drip irrigation equipment, the optimal irrigation quota was 62 mm with a drip irrigation zone spacing of 100 cm.