Effect of soil moisture stress at different stages of growth on yield of corn

To find the effect of water stress on different growth stages of corn, an experimental design was conducted in Karaj Soil and Water Research Station. An experimental model was one factor randomized complete block design with 7 water stress treatments in 3 replications. The corn seeds were 704 single cross and water stress treatments were applied in three different growth stages as vegetative, flowering and yield formation introduced by FAO 33. Water stress treatments were as 30, 60 and 90 percent of soil water depletion in the root zone. These treatments were applied separately at three different growth stages. Normally, the effect of water' stress treatments, cause yield reduction. Results showed that, for 90% depletion of soil water stress during flowering and vegetative growth stages, grain yield decreased markedly. Also this experiment showed that for applying severe water stress in flowering and vegetative growth stages as 90 percent of soil water depletion, grain yield decreased respectively about 70 and 57 percent than control. Maximum yield reduction occurred in severe water stress treatments during flowering period than other treatments. Other yield components decreased with increasing water stress, especially during flowering period. Regarding grain yield, yield components and water use efficiency the sensitive growth stage of corn is flowering and water stress during flowering caused severe yield reduction. Also water stress during vegetative growth decreased grain yield and yield components. Maximum water use efficiency occurred in 30% depletion during all periods and was 1.48 kg/m4. The severe stress treatment (90% depletion) during flowering period had the lowest water use efficiency (0.45 kg/m3). Water stress during flowering period caused severe reduction in grain yield and water use efficiency.