Effects of Deficit-irrigation at Different Stages on Evapotranspiration and Yield of Summer Maize

Abstract

【Objective】 Deficit irrigation is a technology used widely in most arid and semi-arid regions to increase water use efficiency, but how to optimize the timing of and duration of the deficit remains elusive. The objective of this paper is to fill this gap for summer maize grown in the north of China. 【Method】 The field experiment compared three deficit irrigations by controlling the irrigation water amount at 100% (sufficient), 80% (moderate deficit) and 60% (sever deficit) of the potential evapotranspiration measured from a lysimeter (ETa). Each treatment irrigated the crop at emergence-jointing stage, jointing-tasseling stage, and tasseling-filling stage, respectively. Overall, there were nine treatments: moderate deficit irrigation at the jointing-filling stage (T1), severe deficit irrigation at the jointing-filling stage (T2), moderate deficit irrigation at the emergence-jointing and tasseling-filling stage (T3), moderate deficit irrigation at the emergence-tasseling stage and severe deficit irrigation at the tasseling-filling stage (T4), moderate deficit irrigation at the emergence-jointing stage and severe deficit irrigation at the jointing-tasseling stage (T5), severe deficit irrigation at the emergence-jointing and tasseling-filling stage (T6), severe deficit irrigation at the emergence-jointing stage and moderate deficit irrigation at jointing-tasseling stage (T7), severe deficit irrigation at the emergence-tasseling stage (T8), and moderate deficit at the tasseling-filling stage (T8). Sufficient irrigation in all stages was taken as the control (CK). In each treatment we measured the impact of rewatering on evapotranspiration, grain yield and water use efficiency of the crop. 【Result】 Compared with CK, deficit irrigation led to a decrease in evapotranspiration regardless of the stage it was imposed. Rewatering in T3 increased the evapotranspiration to a level comparable to that in CK. T5, T6 and T7 resulted in a permanent reduction in evapotranspiration even after rewatering. To avoid grain yield loss, the soil water content during the tasseling-filling stage should be maintained above 75% of the field capacity. The critical soil water was 50% of the field capacity, below which the water taken up by the crop was unable to sustain its growth. Deficit irrigation reduced the fruit yield by 5.85%～32.25%, compared to the CK, with T3 reducing the least (5.85%). T3 was thus most water-use efficient (2.81 kg/m3), increasing water use efficiency by 4.07% compared to CK. 【Conclusion】 Moderate water deficit at the seedling stage and full irrigation at the jointing-tasseling stage were optimal to improve water use efficiency without significantly reducing grain yield of the maize.

Keywords

• summer maize
• evapotranspiration
• deficit-rehydration
• yield
• water use efficiency