effect of deficit irrigation in different stages of growth on yield of alvand cultivar wheat (case study: hamedan)

abstract due to limited water resources in agriculture, application of each strategy to economize water use and increase area under cultivation is very important. one such strategy is deficit irrigation. for optimal planning of deficit irrigation, it is necessary to determine different sensitive stages of plant water shortages. in this study the effect of deficit irrigation on growth and yield of irrigated wheat (alvand cultivar) in hamedan area was investigated to determine crop yield response factor to water (ky) and performance sensitivity coefficient (λi) elimination of irrigation at varios stages were used. thus the cultivation of winter wheat in farm of bu-ali sina university was under deficit irrigation using a randomized complete block design with six irrigation treatments and three replication during two consecutive years (2004-2006). results showed that low irrigation treatments reduced grain yield, dry matter yield and thousand kernel weight. the flowering period (with sensitivity factor of 1.96) was the most sensitive periods toward water deficit irrigation and the elimination of irrigation in this stage will reduce yield more. elimination of irrigation in milky doughy stage (with a coefficient of reaction 1.67) showed the most performance reaction to the low irrigation. reduction of water use efficiency in these stages in comparison with the complete irrigation in this stages indicates irrigation in these stages are necessary. other results indicate that one irrigation turn may be eliminated in one of the stem elongation or seed hardening stages without any significant decrease in yield and harvest index.