Considering spatio-temporal dynamics of soil water with evapotranspiration partitioning helps to clarify water utilization characteristics of summer maize under deficit irrigation

Continuously increasing the utilization efficiency of agricultural water resources is vital to ensuring future water and food security. Deficit irrigation (DI) could provide a solution to optimize crop water productivity. Research on the spatio-temporal dynamics of soil water coupled with evapotranspiration partitioning is important for clarifying summer maize (Zea mays L.) water utilization characteristics and crop water productivity under different DI strategies, especially in semi-arid regions. Consequently, a three-year field experiment with full irrigation (CK) and eight DI treatments (T1-T8, comprised of combinations of 100 %, 80 %, and 60 % of crop evapotranspiration) was conducted. Data from large-scale weighing lysimeters, micro-lysimeters, and TDR sensors were combined to assess daily root water absorption at different soil depths, actual evapotranspiration (ETa) partitioning into plant transpiration (T) and soil water evaporation (E), and water use efficiency (WUE). Results showed that soil water consumption mainly occurred in the 0-40 cm, 0-60 cm, and 0-80 cm soil layers during the maize growth stages of planting-V6, V6-V12, and V12-R6, respectively. Water absorption above the 60-cm soil depth accounted for more than 92 % of the total water consumption. The appropriate irrigation wetting depth for summer maize could be controlled in the top 80-cm layer to avoid deep percolation. DI affected soil water distribution and availability, and thus decreased soil water consumption rate (WCR) and root water absorption amount. Under moderate water deficit conditions, WCR was rapidly restored to the non-waterstressed irrigation treatment level, and even exceeded that level in the deeper layers after a subsequent irrigation was applied, especially in the early maize growth stages. E/ETa was 31.0-32.5 % under full irrigation. DI decreased total soil water evaporation amount, but increased the E/ETa ratio. The threshold soil water value for defining when maize was subjected to water stress was 22.0 % (72 % of FC) during V3-V12, and 18.0 % (60 % of FC) during V12-R1. Our results suggest that less water was used in T1 (moderate DI) than with the full irrigation treatment. WUE increased by 5.5 %-7.5 % as irrigation amount decreased by 12.3-14.5 % and yield decreased by 3.3 %-8.0 %. These results improve our understanding of maize water consumption characteristics with regard to soil water absorption in different soil layers and evapotranspiration partitioning, and provide implications for efficient water management in arid areas of northwest China.

Automated summary

Studying water utilization efficiency is crucial for ensuring future water and food security, and deficit irrigation is a potential solution. This study focused on understanding the characteristics of water utilization and crop productivity in summer maize under different deficit irrigation strategies in semi-arid regions. The results showed that moderate deficit irrigation can decrease soil water consumption rate and increase water use efficiency.