Silicon contents in soil and in highland rice plants under different doses of silicon and nitrogen fertilization

The element Silicon is not deemed essential for plant growth and development, but its absorption can benefit cumulative cultures like rice greatly. The Si content of tropical soils, however, is very low, due to the advanced weathering degree. The objective of this work was to evaluate the growth of rice plants in highlands under plastic tunnels and the effects of nitrogen (N) and Si doses on dry matter production, grain productivity, N content; Si soil and plant contents; and on the amount of extracted silicon. The treatments consisted of three doses of N (5, 75, and 150 mg kg(-1) of soil) in urea form and four doses of SiO2 (0, 200, 400, and 600 mg kg(-1) of soil) in calcium silicate form (Wollastonita). The completely randomized experimental design in a 3x4 factorial scheme was carried out in five replications. Dry matter accumulation, grain yields, and N contents in the plant were not influenced by the silicon doses. Increased nitrogen fertilization raised the dry matter production, productivity grains, and N plant contents, but had no effect on Si soil contents. There was an N x Si interaction in relation to the Si plant content and the amount of Si accumulated by the plant.