施硅对稻田土壤氮矿化的影响

供试土壤分别采自日本山形县农业试验场（土壤A）和鹤冈市吉田农户的水稻田（土壤B）。将两种水稻土分别与硅酸钙和硅酸混合，在密闭条件下恒温培养4周，测定施硅对土壤氮矿化的影响。在培养土壤中加入^15N标记硫酸铵以评价施硅对加入土壤中氮去向的影响，结果表明：在培养1周内，施用硅酸钙1g.kg^-1,2g.kg^-1与不施硅相比，土壤 fu lk 0。2-0。3，NH4^ -N总积累量分别增加20%，26%（土壤A）和9%，11%（土壤B），土壤氮净矿化速率分别增加26%，35%（土壤A）和13%，13%（土壤B）。处理间差异在培养开始后的第1周大于第4周，硅酸对土壤pH及氮矿化速率没有影响，两种硅肥对施入土壤中氮的去向均无明显影响，研究结果揭示，硅酸钙促进土壤氮矿化的原因不是硅元素本身，其可能机制是通过增加土壤pH而加速氮的矿化。

Nitrogen mineralization in two paddy soils as affected by silica source addition

The beneficial effect of Si on rice growth had been confirmed by many documents.However,the information on the relationship between Si fertilizer application and the availability of soil N was little.Two paddy soils were mixed with different sources of Si fertilizer (calcium silicate and silicic acid), and incubated under completely closed condition.15N labeled ammonium sulfate was added to evaluate the fate of N applied with respect to Si application.From 0 to 1 week after incubation,calcium silicate application increased the soil pH by 0.2-0.3 unit as compared to no Si application.Total accumulation of NH4+-N was increased by 20%，26% in soil A and 9%,11% in soil B,and the net rate of N mineralization was increased by 26%, 35% in soil A and 13%,13% in soil B by addition of calcium silicate at the rates of 1 and 2 g kg-1,respectively.The difference in soil pH and N mineralization among treatments was more significant at the first week than at the 4th week after incubation.Silicic acid had no effect on soil pH,ammonium accumulation and the rate of N mineralization.Data suggested that calcium silicate fertilizer accelerate the N mineralization not by Si element but through its effect on soil pH.