M.A. Thesis:

Effect of foliar application of potassium humate and zinc on yield٫ yield components and protein content of forage sorghum

In order to evaluate the effect of foliar application of potassium humate and chelated zinc on yield, yield components and protein content of forage sorghum, a factorial experiment based on randomized complete block design with three replications was done in Sabzevar. Experimental factors included foliar application of potassium humate and chelated zinc, each in three levels of non-foliar application, foliar application at 6-8 leaf stage and two foliar applications at 6-8 leaf stage and emergence of inflorescences. Potassium humate and chelated zinc were foliar applied at concentrations of 0.03% and 0.1% respectively. The results showed that foliar application of potassium humate had no significant effect on tiller number per plant, but considerably increased plant height, leaf number per plant, fresh forage yield, forage dry matter percentage, forage protein content and nitrogen uptake compared to control treatment. Chelated zinc foliar application significantly increased plant height, leaf number per plant and fresh forage yield in comparison to control, but decreased tiller number per plant, dry matter percentage and protein content of forage. The foliar application of chelated zinc had no significant effect on nitrogen uptake. There were no significant differences between the number of potassium humate and chelated zinc foliar application in relation to the studied traits. The highest number of leaves per plant and the nitrogen uptake by sorghum were obtained in two foliar applications of potassium humate at 6-8 leaf stage and emergence of inflorescences combined with foliar application of chelated zinc at 6-8 leaf stage. Potassium humate foliar application in the 6-8 leaf stage had the highest percentage of protein in forage. However, the highest dry matter percentage of forage was observed in two foliar applications of potassium humate at 6-8 leaf stage and emergence of inflorescence, which did not show significant difference with potassium humate and chelated zinc foliar application in 6-8 leaf stage. According to the results, foliar application of potassium humate and chelated zinc at beginning of vegetative growth (6-8 leaf stage) is recommended for production of maximum fresh and dry forage of sorghum.

Keywords: Humic acid, nitrogen uptake, sorghum, forage quality, micronutrients