酸化与富磷对农田土壤硅有效性的影响

目前，大量农田土壤及其生态功能正经受着土壤酸化的严重威胁，而土壤pH深刻影响着土壤中硅、磷养分的移动性及两者间的相互作用。关于硅肥施用可有效提升土壤磷素植物有效性的研究已有大量报导，但在农业集约化生产区，土壤磷素已大量累积的背景下，磷富集对土壤硅移动性与有效性的影响及其机制尚不清楚。选取2种不同有效硅水平的农田土壤（低有效硅土壤LASi：有效硅28.20 mg?kg-1；高有效硅土壤HASi：有效硅253.6 mg?kg-1），通过等摩尔浓度硅磷竞争吸附试验、土壤培养试验等，探究人工酸化与磷添加对土壤硅吸附性能与移动性的影响及其机制。结果表明，酸化土壤pH在3.5~8.0范围内，当硅与磷等摩尔浓度同时添加时，磷的存在会降低硅的吸附，各相应pH的LASi与HASi 2种土壤对硅的吸附量分别降低26%~74%、31%~84%。这说明，土壤对磷的吸附大于对硅的吸附。设置土壤pH3.5~8.0范围内，降低pH可降低土壤对硅的吸附；磷添加降低土壤硅吸附的效应，在高pH条件下更为显著。土壤酸化与磷添加降低了土壤对硅的吸附，降低了土壤有效硅（HOAc-NaOAc-Si）水平；不同类型土壤移动性硅（CaCl2-Si）水平对酸化与磷添加的响应不同，具体机理尚需进一步研究。

Acidification and Phosphorus Enrichment Affect Silicon Availability in Two Farmland Soils

【Objective】Soils and their functions are under threat from acidification. Phosphorus (P) and silicon (Si) mobility and their interactions in soils are sensitive to soil pH. Although Si fertilizer application has been reported to efficiently increase P availability in soils, the responses of Si mobility and availability to soil P enrichment are not well understood, especially in areas of intensive agriculture where soil P accumulation is significant.【Method】This study investigated the effects of P addition and artificial soil acidification on Si sorption and mobility in two typical farmland soils with different available silicon levels (the lower available silicon level, LASi and the higher available silicon level, HASi) using P and Si competitive adsorption experiments and soil incubation experiments.【Result】When Si and P were simultaneously added at equimolar concentrations between pH 3.5 and 8.0, the presence of P decreased Si adsorption by 26%-74% and 31%-84%, respectively, in LASi and HASi soils at the corresponding pH, suggesting that P had a greater affinity to soil solids than did Si. Si sorption by the soil generally decreased with decreasing pH in the pH range of 3.5 to 8.0, and the reduction of Si sorption due to P addition was more significant under higher pH conditions. 【Conclusion】Soil acidification and P addition decreased Si sorption and the soil HOAc-NaOAc-extractable Si content. The responses of soil CaCl2-extractable Si content to soil acidification and P addition were different between the two farmland soils, and further studies are needed to understand the mechanisms.