Varietal Water Use Efficiency Differences Among Spring Wheat Varieties in Two Montana Cropping Systems.

This study aimed at evaluating  water use efficiencies (WUE) differences among five varieties of spring wheat as related to N fertility and the type of cropping systems (Continuous, and Crop-Fallow). The two year-study was set at four geographical locations in a Split-split-plot design arranged in randomized complete blocks with four repetitions. The main plot factor was cropping system with two levels (Fallow-crop, Continuous Cropping), the sub-plot factor was N rate (4 levels), and the sub-subplot factor was spring wheat variety (5 varieties). Gravimetric water contents in the 0-120 cm soil profile were determined at the onset and at the end of each growing season. In-season precipitations were measured using a rain gauge. Results show that there is a genetic variability for water use efficiency among the five varieties evaluated. Cultivar WB 9668 displayed the highest WUE. Nitrogen fertility and cropping systems did not affect water use efficiency.