The availability and leaching risk of phosphorous after paddy field conversion to upland in hilly red soil area of south Hunan Province
[Objective]This study investigated the variation of soil P availability when the field become upland from paddy field,and the major factors causing the variation.The research will provide a basis for academic phosphorus fertilization in the uplands.[Methods]Soil samples were collected in the paddy fields developed from parent materials of limestone,quaternary laterite and sand shale,and in the neighboring uplands derived from paddy fields,respectively.The total,available,and water-soluble P content,and the contents of inorganic P fractions(Al-P,Fe-P,Ca-P,and O-P)were analyzed.Principal component analysis(PCA)and random forest analysis method were used to evaluate the contribution of soil properties to the change of P availability,and to screen the main factors causing the variation.[Results]After transferred from paddy field to upland,the available P content in the quaternary laterite-developed soil was not changed significantly,neither the tested inorganic P fractions.While the available P contents in limestone-and sand shale-developed soils were increased by 20.48 and 17.60 mg/kg(P<0.05),and soil phosphorus activation coefficients increased by 2.67 and 2.22 percent points,the Al-P increased by 46.07 and 51.28 mg/kg,Fe-P in limestone-developed upland was increased by 62.11 mg/kg.The water soluble P contents in all the three uplands were not exceeding the P risk threshold.According to the correlation analysis result,the P activation coefficients in the derived uplands were positively correlated with Fe-P(P<0.05)and Al-P(P<0.01).PCA and random forest analysis showed that Fe-P and Al-P were the main factors driving the change of availability of soil phosphorous.[Conclusions]In the hilly area of southern Hunan Province,transferring paddy fields to uplands has caused increase of the phosphorus availability in limestone-and sand shale-developed red soils,due to the enhanced proportion of Fe-P and Al-P in total P,not in the quaternary laterite-developed red soil.The water soluble P contents in all the transferred uplands are lower than the P risk threshold,showing low risk of soil P leaching.
red soilparent materialtransferring paddy field to uplandphosphorus availability coefficientinorganic P fractionP leaching risk
万方数据
维普
