GAINS IN YIELD AND ITS COMPONENTS UNDER NORMAL AND LIMITED IRRIGATION OF MEXICAN WHEAT CULTIVARS

Availability of irrigation water for wheat-producing areas in Mexico is limited, but wheat (Triticum aestivum L.) demand keeps increasing, and thus water needs are greater. This study tested 16 bread wheat cultivars released from 1940 to 2015 and recorded their grain yield and its components. Four field trials were established during the 2014-2015 Fall-Winter crop season. Two trials were sowed in Montecillo, state of Mexico and two in Celaya, Guanajuato, and two sowing dates were tested: optimum and late. The experiments were arranged in random blocks under a split plot design. Main plots were irrigation levels, and small plots were cultivars. Under limited irrigation, most treatment combinations did not show significant differences in yield and its components, except for late-sown wheat in Celaya. Combined and sowing dates analyses revealed significant differences among irrigation levels for all the variables recorded. Limited irrigation affected grain yield, aerial biomass, and number of grains per m(2); their reduction was 20.3, 16.8, and 14.5 %, respectively. Annual average yield increased 1.21 % (41.77 kg ha(-1)); in 67 years, the accumulated yield increment is 2.8 t ha(-1) Rate of yield improvement decreased under normal irrigation (1.10 %) compared to the rate under limited irrigation (1.35 %). These results suggest that less water may produce the same yield in the future, and current water volume could support a wider cultivated area.