Determination of the best time of cotton irrigation in the East of Mazandaran province

In order to determine the best time of cotton irrigation in East of Mazandaran province, an experiment, conducted for 3 successive years in agricultural research station of Baykola. Six treatments and four replications were carried out with randomized complete block designs for Sahel variety. Water treatments were carried out based on, I0: no irrigation, I1: once irrigation in boll opening stage, I2: Irrigation in boll stage, I3: once irrigation at flowering stage, I4: Twice irrigation (flowering and boll stage) and I5: three time irrigation (flowering stage, boll stage and boll opening stage). Comparison and analysis of variance results of 3 consecutive years’ experiments showed that the effect of irrigation treatments on cotton yield at 1% level was significant. The results shows that water consumption in treatment I3 has been reduced 49% comparing to treatment I3, while the crop yield reduced only 23%. Given the existence of water resources restriction, I3 treatment is known as a best treatment. Given no restrictions on water resources, I4 treatment is introduced as a best treatment. By use of 3 successive years collected data, plant sensitivity factor (Ky) was estimated to 0.84.