To determine effects of methanol foliar application on soybean grain yield under, a factorial split-plot experiment based on a randomized complete block design with four replications was done at Research Field of Faculty of Agriculture and Natural Resources, Islamic Azad University-Karaj Branch, Karaj, Iran, during 2010. The first factor was drought stress in two levels (based on depletion of a1=40% and a2=70 % of available soil moisture). The second factor was spraying times of methanol in two levels (in the morning at b1= 8-10 AM and in the evening at b2=19-21 PM). Third factor was foliar application number of methanol with three levels (each c1=7, c2=14 and c3= 21 days, Methanol spray was applied 5, 3 and 2 times during growth season of soybean, respectively). All treatments were sprayed with 21% (v/v) methanol concentration. 2 g lit-1 Glyine was added to prepared solutions. Grain yield, biomass, harvest index, 1000-grain weight, protein and oil percentage and yields were measured in this study. The results showed that there was significant (p>0.05) differences between effects of drought stress level on measured parameters. Under normal irrigation, the highest (3187 kg ha-1) and lowest (1526 kg ha-1) soybean grain yield was obtained in a1 and a2, respectively. Results of oil yield indicated that a1 and a2 were produced the most (731 kg ha-1) and least (484 kg ha-1), respectively. Besides, results showed that significant differences exists (p>0.05) between interaction effects a*b, a*c, b*c and a*b*c in some traits, as under normal and deficit irrigation maximum grain yield were observed by methanol spraying every other week in the evening and every 7 days in the morning, respectively. It seems applying aqueous solutions 21 % (v/v) methanol on water deficit condition on different periods on soybean plants and time application can reduce harmful effects of drought and improve plant potential to cope with stress.
