Factors of vivianite formation on rice roots

水稻秧苗移栽和淹水后，稻田耕层土壤减少。在还原性条件下，耕层土壤中部分磷酸盐结晶为活钙石。利用钒钛在稀酸中加热转化为难溶物质的事实，建立了一种定量测定钒钛含量的方法。在低地土壤中，如灰质低地土壤和灰质低地土壤中，薇薇石的形成比在火山灰土壤中更为常见。耕层土壤在季中排水和排水后氧化时，橄榄石含量下降。

The plow layer soil of paddy field is reduced after transplant of rice seedlings and submergence. Under the reducing conditions, a part of phosphate in the plow layer soil crystalized as vivianite. A quantitative method to estimate the content vivianite was developed using the fact that vivianite is converted to a sparingly soluble material in the dilute acid with heating. Vivianite formation is more common in lowland soils such as gley lowland soils and gray lowland soils than in volcanic ash soils. The vivianite content decreased during midseason drainage and after drainage when the plow layer soil is oxidized.