The sensitivity of growth and yield of dwarf wheat to water stress at three growth stages

Summary Response of dwarf wheat (Triticum aestivum L. em Thell) to three different levels of water stress at three growth stages — seeding to maximum tillering, maximum tillering to flowering and flowering to maturity, was studied under field conditions for two seasons. At each of these three stages, plants were subject to three ratios of irrigation water to cumulative pan evaporation (IW/CPE) –0.45, 0.60 and 0.75. During the remaining stages the plants were irrigated with an IW/CPE ratio of 0.9. Thus mild, moderate and severe stress treatments were compared with a no-stress control. At all stages moderate and severe water stress decreased plant height, leaf area, ear number, 1000-grain weight, grain yield and water-use efficiency. In stage 3 the effect of water stress on straw yield was not marked. Wheat was most sensitive to water stress during stage 1 when the reduction in grain yield was caused by a reduction in numbers of ears and grains per ear. In stage 2, grain yield reduction was due to fewer grains perear and a lower 1000-grain weight. On rewatering, mild stressed plants showed recovery of plant height, tiller number and in consequence, yield. Results indicate that under the conditions of this study the wheat crop should be irrigated at a IW/CPE ratio of 0.75 when water resources are limited. With an unlimited water supply the ratio may be increased to 1.2 in stage 2 to maximise the yield.