干旱区生态环境知识资源中心

Studying the responses of water evaporation rate to climate changes in corn fields located in arid regions can effectively provide the scientific basis for the formulation of the appropriate irrigation strategies and for increasing the efficient use of water resources. In this study, three representative climate regions located in Yanqi, Shanshan and Qinghe Counties in the arid regions in northwest of China were studied to investigate the indicative threshold values of the environmental factors that cause significant changes in soil water evaporation rate in corn fields in the summer by monitoring on-site the daily changes in soil water evaporation rate in corn fields, liquid flow rate in corn stalks, water content within 1m-soil layer underneath topsoil, and the meteorological factors including air temperature (T-air), atmosphere relative humidity (RH), and wind velocity (Wv). The study results indicated: (1) when soil water content was higher, a phenomenon of short "Afternoon break" in water evaporation existed in the corn fields in Shanshan and Yanqi Counties where mean annual T-air was higher but this phenomenon did not exist in corn fields in Qinghe County where mean annual T-air was lower. There existed a phenomenon of no-liquid flow and transpiration in corn evaporation rate at noon. High temperature was favorable for corn growth. When soil water content was lower, no "afternoon break" existed in soil water evaporation in corn field and corn transpiration rate in three counties. Low temperature was favorable for corn growth; (2) there were significant correlations between soil water evaporation rate in corn fields and T-air, W-v, soil temperature (T-s) and RH. There were significant correlations of corn transpiration rate with T-s, RH and Tair; (3) Temperature at 22.59 degrees C was the minimum threshold for Ts that affected the changes in corn transpiration rate. When soil water content was 22.73 %, corn respiration rate was the highest. Planting two rows of crops with higher height such as sorghum and sunflowers in outside boundary of corn fields, simultaneously controlling irrigation frequencies and irrigation amounts and increasing T-s and RH to maintain soil water content at about 22.73%, may be the effective ways to reduces soil water evaporation rate and increase corn transpiration rate.