Abstract: Examining the effects of silicon fertilizer on the yield of double-cropping rice and the leaching loss of soil nitrogen (N) and phosphorus (P) could provide a basis for the optimization of formula fertilizer and the comprehensive control technique of agricultural surface source pollution in typical double cropping paddy field. A field experiment was conducted to investigate the effects of silicon fertilizer of 0, 750, 1500, 2250 and 3000 kg·hm^-2(T₀, T₁, T₂, T₃, T₄) on yield and N and P absorption of double-cropping rice, dynamics of N and P in the field surface water, soil available silicon, organic matter, alkali nitrogen and available phosphorus under the fixed nitrogen and phosphorus fertilizers. The results showed that compared with control (T₀), the silicon fertilizer increased the yield of early and late rice by 2.2%-30.4% and 3.9%-9.2%, respectively, enhanced rice N accumulation increased by 2.4%-47.3%, rice P accumulation by 2.2%-41.3%, straw N accumulation by 0.4%-28.3%, and straw P accumulation by 5.1%-31.0%. On the first day after fertilization, the total nitrogen (TN) content in the surface water was decreased by 3.4%-28.8% in silicon treatments compared with T₀, the ammonium nitrogen (NH₄⁺-N), total phosphorus (TP) and total soluble phosphorus (TDP) was decreased by 10.4%-25.6%, 25.5%-29.2%, 30.8%-38.0%, respectively. 45 days later, TP and TDP contents in the field surface water were significantly higher than T₀. The silicon fertilizer treatment was beneficial to increase soil silicon level, contents of organic matter and alkali nitrogen of the double cropping rice, among which the T₁ treatment performed the best. Soil available phosphorus showed a decreasing trend with the increasing silicon fertilizer.

Key words: silicon fertilizer, nitrogen (N) and phosphorus (P), soil, rice, surface water