The Effect of Silicon Fertilization on Reducing Salt Stress in Rice (Oryza sativa L.)

Soil salinity is one of the most significant abiotic stress factors that adversely affect yield and quality. Silicon (Si) is known as a nutrient element reducing the deleterious effects of these stresses in plants. The objective of this study was to investigate the effect of salt x Si interaction on rice yield, the effect of salinity on available Si content of soils and the reducing effect of silicon on salt induced-stresses. For this aim, 5 different soil samples were taken from rice grown soils around Samsun. To obtain the different salt levels in soils, a salt mixture of Na2SO4:NaCl:CaCl2:MgSO4 at the 9:5:5:1 ratio were added into the soil 1, 2, 3, 4, and 5 to reach 10.27, 3.55, 10.98, 5.75 and 7.22 dS m(-1) EC values, respectively. A greenhouse experiment was conducted in factorial experimental design (2 x 5) with three replicates in each soil with growing rice plant. In each salt level (non-saline and saline) 0, 50, 100, 200, and 400 mg Si kg(-1) as silicic acid (H4SiO4) were given into the soils. Also, NPK fertilizations according to the soil analyses were made to obtain the same levels of these elements in each soil. Increases in the mean grain yield upon silicon fertilization ranged between 55.5% for the soil having 3.55 dS m(-1) EC and 2.31% for the soil having 10.98 dS m(-1) EC. The salt x Si interaction was significant in 4 soils and the optimum Si rate for each soil was dependent on salinity levels of the soils. Increments in the available Si concentration of soils and the rice grain yield by silicon fertilization decreased with increasing EC values of soils. While silicon decreased Na concentration of rice grain; K concentration increased; Ca, Mg and P concentrations did not show any distinct tendency. Rice grain yield had a significant negative relation with Na content (R = - 0.664) while silicon fertilization increased the ratios of K/Na, Ca/Na, Mg/Na and P/Na. Consequently, it was determined that the optimum Si dose for rice grown in saline soils was 200 mg kg(-1) and silicon fertilization could be a practical way of reducing the deleterious effect of soil salinity and alkalinity in rice cultivation.