Regulated Deficit Irrigation Application and the Physiological Responses of Cotton in Southwest Texas.

The urban water demand in Southwest Texas is increasing rapidly in recent years due to the population increase in this area. One possible way to assist in solving this problem is to reduce the agricultural water use; however, the crop yield should not be affected. Regulated deficit irrigation (RDI) is a widely used measure for saving water and maintaining crop yield. According to the previous research at Uvalde, approximately 25% irrigation water can be saved. An experiment with seven treatments, including five ¡®fixed¡¯ and two ¡®dynamic¡¯ irrigation schemes, were developed in 2008 to test whether more water can be saved on irrigation, and how the four different cotton cultivars responded to the different RDI schemes. The data analysis showed that: 1) the ordinary RDI threshold should stay between 0.7 and 0.8. With dynamic RDI, possibly half of the ET replacement is sufficient for cotton production (without affecting the yield). 2) dynamic RDI can improve the plant growth by reducing the drought stress. 3) the variety effect is not as obvious as irrigation scheme. Actually, the variety effect was only detected on lint yield in this study. No interaction was detected. Thus in the future RDI study, the variety may not be a very serious concern in the experimental design.