Effect of Mepiquat Chloride (Pix) and Nitrogen on Cotton Yield and Yield Components Under Water Stress Conditions.

To study the effect of different Mepiquat Chloride (Pix) levels and nitrogen rates on the yield and seed quality of cotton under water stress conditions, a two year field experiment was conducted in Cotton Research Station of Hashem-abad, Gorgan, in 2004 and 2006. The treatments were arranged in a split-factorial design with three replications. In this study, cotton (Gossypium hirsutum var. Siokra ) was treated with irrigation frequencies of 12 and 24 days, and without irrigation as main plots. In each main plot, two levels of Pix (0 and 1.5 l ha^-1), 50% of recommended N level, recommended N level, and 50% more than recommended N were used as factorial arrangements. The seeds from 2004 were planted in 2005 in a randomized complete block design with factorial arrangements. Results showed that except vegetative branch, the effect of irrigation frequency was significant on the other measured traits. Also, application of 100 kg N ha^-1 produced the highest amount of cotton seed compared to the other N levels. Application of pix reduced plant height and produced more yield in the first picking than the second one.