چكيده لاتين :
In order to study the effect of delayed irrigation in primary stages of growth on yield and yield components of Corn, an experiment was conducted in agricultural research center of Khorasan (Torogh). This research was clone in 3 separated experiments in randomized complete block with 5 replications. Each block was an indicator of a water stress treatment. Varieties consisted of single cross hybrids of 704, 647, 604 and 301. Date of planting was 23rd Ordibehesht for all experiments (14). In experiment (I), irrigation started from the beginning of the planting, according to the plant needs (50% allowable water depletion) uptothe end of plant growth, and in experiment (2) and (3) first irrigation was done in 70% and 90% of allowable water depletion. Results showed that the varieties had significant differences in their morphology and physiology. Stress up to 70% allowable water depletion (1,2) resulted to decreasing attributes such as plant height, ear height, number of total and also upper leaves, number of seed row per ear and increasing stem diameter, ear length, ear diameter, wood diameter, number of seed per row, weight of 1000 seed, seed depth and harvest index in most varieties. Also yields of varieties 704, 647, 604 and 301 were 11.959, 11.745, 12.09 and 10.201 ton per hectare compared to control having the averages of 11.473, 11.489, 11.971 and 10.033 ton per hectare improved significantly.
Stress intensity up to 90% allowable water depletion (3) resulted to increased characters like as stem diameter, number of seed row and decreased other characters in the most varieties compared to control. Yields of varieties under this treatment decreased. This decrease was significant just in varieties 704 and 301. Based on results, it will be possible to delay second irrigation up to 70% allowable water depletion. In case of water limitation, variety 647 can be used for its better yield with regard to the others and donʹt have significant difference with control. In this case the second irrigation up to 90% allowable water depletion will be delayed. Also it seems that the variety 647 has more resistance to water stress than the others.
