Rice (Oryza sativa L.) Tolerance to Drought Can be Improved By Silicon Application.

Being located in the semi-arid region and characterized by high mean annual temperature and low mean annual precipitation, drought is inevitable in Egypt. Rice (Oryza sativa L.) is the second most consumed cereal after wheat in Egypt. The aims of this work were to assess the effect of drought on rice growth and productivity, and the impact of silicon application on rice tolerance to drought stress. A completely randomized design pot experiment with three replications was conducted in a clay soil with five levels of soil moisture content (SMC) (70, 80, 90, 100, and 120% of the soil saturation point) and five rates of Si (0, 2.1, 4.2, 6.3, and 8.4 mg Si/10 plants). Plant height, rice straw, root yield, and grain yield significantly reduced with 32, 52, 36, and 27%, respectively, when SMC was reduced from 120 to 70%; however, Si supply significantly increased them with 38, 97, 49, and 106%, respectively, when Si rate increased from 0.0 to 8.4 mg/ 10 plants. Under no Si application, nutrients (N, P, K, and Si) concentrations in straw were reduced by 75, 37, 30, and 39%, respectively, when SMC was reduced from 120 to 70%. However, in SMC of 70%, N, P, K, and Si concentrations in straw increased by 42, 59, 36, and 53%, respectively, when Si rate increased from 0.0 to 6.3 mg/ 10 plants. The combination between SMC of 120% and Si rate of 8.4 mg Si/10 plants and SMC of 70% and Si rate of 0 mg Si/ 10 plants gave the maximum and minimum plant growth characteristics and nutrients concentration, respectively. Obviously, grain yield and biomass of rice could be maintained when decreasing water supply, if Si were supplied.