The Effect of Organic and Chemical Nutrition Methods on Forage and Grain of Millet (Panicum miliaceum L.) under Terminal Drought Stress

Investigating the crop response to the deficit irrigation and evaluating the effect of drought stress on plant is one of the most important issues in crop production. In these circumstances, the use of organic fertilizers can play a mitigative role. Hence, an experiment was laid out as split plot based on randomized complete blocks design with three replications in Research Farm of University of Gonabad, Gonabad, east of Iran. The main factor comprised of full irrigation, temporary interruption of irrigation in the flowering stage, and temporary interruption of irrigation in the seed filling stage, and subfactor levels included of control, chemical fertilizer, manure, compost, and vermicompost. Drought stress led to decreases in grain and biological yield of the millet, and the highest yields were achieved by vermicompost application under full irrigation during the growth period. The forage yield, plant height, leaf number in the main stem, tiller number, and 1000 grain weight were not significantly affected by the drought stress. The forage, biological and grain yield showed the highest increase due to applying vermicompost, while the plant height and harvest index showed the highest increase when exposed to manure. Chemical fertilizer enhanced the tiller number to a greater value as compared to other treatments. The plants that were exposed to drought stress in the grain filling stage showed notable decreases in the harvest index. The water use efficiency of the plants exposed to drought stress in the flowering stage was increased, whereas in those exposed to drought stress in the grain filling stage it was decreased. Vermicompost and compost had the greatest positive influence on the water use efficiency. In general, even though the highest yields were obtained from full irrigation, with utilizing deficit irrigation operation in the flowering stage of millet we can improve the water use efficiency and the harvest index of this crop. In addition, the findings showed the positive effects of organic amendment in comparison with chemical amendment for millet cultivation.