Effect of Mixed Cropping of an Early- and a Middle-ripening Wheat Cultivar on Mitigation of Competition during Post-anthesis Moisture Stress

A two-year field experiment was carried out in semi-arid region of southern Iran (Shiraz), during 2007-2008 and 2009-2010 growing seasons using various mixtures of an early- (cv Falat) and a middle-ripening (cv Shiraz) winter wheat cultivar to evaluate the beneficial effects of inducing temporal growth heterogeneity on reduction of intra-specific competition during post-anthesis moisture stress conditions. Treatments were composed of five combination ratios of the two cultivars (1:0; 2:1; 1:1; 1:2, 0:1), and two levels of post-anthesis moisture conditions i.e. equal to Field Capacity and 50% FC. The results showed that the equal ratio (1:1 mixed cropping of early and middle-ripening cultivars) was superior in grain yield components as well as post-anthesis water use efficiency (PWUE) among the mixture treatments. It appeared that mixed cropping of early- and middle-ripening cultivars had the potential for altering the intensified competition under deficient moisture conditions and may improve PWUE. Additional research for determining the best choices of cultivars, mixing ratios, sowing date, phenological differences, input requirements, and management practices for each regional environment are essential to achieve the maximum benefits.