Comparison of Soil Water Withdrawal Patterns and Water Use Efficiency of Alternative Crops Grown Under Deficit Irrigation.

Adoption of water-conserving strategies such as growing drought-tolerant alternative crops together with high-value crops is a possible solution in improving agricultural productivity. Evaluation of water use of a crop is necessary in assessing its potential under limited water conditions. In this study, soil water extraction patterns, agronomic yield, harvest index (HI), and water use efficiency (WUE) of cotton and three alternative crops (guar, sesame, and sorghum) grown under four different levels of deficit irrigation (DI; extreme-51 mm, severe-127 mm, moderate-203 mm and mild-279 mm) were compared. Results showed that for all crops, substantial soil moisture depletion and soil water extraction occurred deeper in the soil (40 cm depth and below) at start of reproductive stage towards end of growing season. The depth of soil water extraction was not affected by DI treatments throughout the growing season. Total water extracted (averaged over 20 to 100 cm depths) did not vary among DI treatments for all crops except guar, which showed highest total water extraction at severe DI treatment. There was a significant crop-by-irrigation interaction in yield, but no significant interactions were observed in HI and WUE. For guar and sesame, yields among treatments were statistically similar but for sorghum, yield significantly increased as irrigation level increased. Lint yield of cotton under moderate DI was comparable to severe and mild DI treatments. The highest HI was observed under the two lowest DI levels and were not significantly different to the HI obtained under moderate DI treatment. The highest WUE was observed under severe DI treatment which was not significantly different to WUE of crops grown under extreme and moderate DI treatments. Therefore, additional in-season irrigation after a certain level is not required to produce potential yields and adoption of deficit irrigation can improve WUE for the crops tested in this study.