Effect of humic and salicylic acids spraying on some morphological characteristics, yield and yield components of sorghum (Sorghum bicolor L.) in different levels of irrigation

In order to evaluate the effect of humic and salicylic acids spraying on some morphological characteristics, yield and yield components of sorghum (Sorghum bicolor L.), a split split plots experiment based on RCBD design with three replications was conducted in 2015-2016 growing seasons, in University of Gonabad, Iran. The main plots, sup plots and sub sub plots included different levels of irrigation in three levels (full irrigation, cuting irrigation at flowering stage and grain filling in the end of growth season stages), humic acid in two levels (0 and 6 liter.ha-1) and salicylic acid in two levels (0 and 1 mMol), respectively. The results showed that cutting irrigation at flowering and grain filling stages decreased seed yield 30% and 51% compared to control, respectively; while it did not effect on biological performance and harvest index. Simultaneous application of humic and salicylic acids improved most of the studied traits, so that the highest plant height (207.16 cm), tiller number per plant (1.88), seed number per panicle (1854), 1000 seeds weight (40.20 g) and seed yield (2838.67 kg.ha-1) in application of humic and salicylic acids treatment in the full irrigation conditions were obtained. Cross-sectional stress treatment in the grain filling stage and non-application of humic and salicylic acids had the highest rate of harvest index (29.47%). The highest biological yield (15802.7 kg.ha-1) was obtained under full irrigation and humic and salicylic acids application conditions. Also, the most positive and significant correlation was observed between seed number per panicle and the plant height (r= 0.97**) . According to the results of this research, it is recommended touse 6 liter.ha-1 humic acid and 1 mmol salicylic acid spraying to improve growth and yield of sorghum plant in drought stress conditions.