Effect of Silicon on the Adsorption/Desorption of Phosphorus in Alkaline Paddy Soil

In order to apply silicon and phosphorus fertilizer rationally,promote farmland nutrient management,reduce non-point pollution from crop production,the effect of added silicon on the adsorption/desorption of phosphorus in alkaline paddy soil was investigated.The adsorption/desorption isotherm experiments of phosphorus in alkaline paddy soil at different silicon levels were conducted,and the HCl was used to neutralize the alkalinity of K2SiO3,and the different concentrations of Cl-and K+ between treatments were balanced with the addition of NaCl,thus the effects of pH and accompanying ions by added silicate on phosphorus adsorption were eliminated.Results showed that Freundlich and Temkin adsorption models could fit well to simulate the phosphorus adsorption/desorption at different silicon levels,and Freundlich equation was better than the Temkin model.The phosphorus adsorbed amount decreased obviously with the increase of silicon.While silicon was added at 30 or 120 mg L-1,the phosphorus adsorbed amount reduced respectively 3.08%-18.23% and 7.62%-20.58% compared with control.The constant ka and na of Freundlich adsorption equation were declined,which illuminated the desorption quantity and intensity decreased to different extent.The values of the hysteretic coefficient,indicating the desorption characteristics,were all lower and the desorption quantity of phosphorus higher with the addition of silicon.While silicon was applied at 30 or 120 mg L-1,the phosphorus absorbed proportion separately reduced 3.08%-18.23% and 7.62%-20.58% compared with control.The addition of silicon decreased the amount phosphorus adsorption and increased its desorption in alkaline paddy soil,at least under the experimental conditions studied.