Agronomic and Physiological Characteristics of Forage Sorghum (Sorghum bicolor L.) under Water Deficit Stress and Silicon Fertilizer

IntroductionThe quantity and quality of forage plants are beneficial and useful due to their role in animal husbandry, reproduction and other livestock products. Due to the limitation of water resources, water-deficit as a significant biotic stress is the most severe threat to world food security and is responsible for many yield losses. Plants constantly modify their physiological processes in response to various biotic and abiotic stress to regulate the balance between plant growth and defense response. Many researchers have documented that plant nutrients are involved in biological processes of plants. It has been stated that the use of silicon by increasing the ability to absorb water can be useful to improve drought tolerance of sorghum, sorghum can with the help of silicon extract more water from dry soil and maintain more stomatal conductance.Materials and MethodsIn order to evaluate the effect of silicon fertilizer on the quantitative and qualitative yield of forage sorghum (Sorghum bicolor L.) under water-deficit stress, a split-plot experiment was performed in a randomized complete block design in at the research farm of Varamin, Iran in 2017-2018. The treatments included irrigation in three levels irrigation in field capacity and irrigation at 60% and 45% of field capacity (which were named as full irrigation, moderate and severe water-deficit stress, respectively) as the main plot and silicon fertilizer (Potassium Silicate) in three levels, non-use (control), silicon foliar spraying (three per thousand), and silicon fertigation (10 L ha-1) as the subplot. Silicon spraying with a ratio of three per thousand and silicon irrigation fertilizer at the rate of 10 liters per hectare were considered in three stages.Results and DiscussionThe highest (4.51) and lowest (2.88) leaf area index were achieved in silicon fertigation treatment under full irrigation and none fertilizer treatment and severe water-deficit conditions, respectively. Based on the obtained results, the highest total chlorophyll content (1.73 mg g-1 FW), relative water content of leave (88.08%), stomatal conductance (2.46 cm s-1) were achieved in fertigation treatment under full irrigation conditions. The results show that the amount of electrolyte leakage increased due to water-deficit stress, but silicon fertilizer decreased the adverse effect of stress conditions. The lowest level of electrolyte leakage (341.3 µS cm-1) was obtained from the full irrigation and fertigation treatment.