长期施磷对山原红壤磷库组成及有效性的影响

EFFECTS OF LONG-TERM FERTILIZATION ON FORMS AND AVAILABILITY OF PHOSPHORUS IN MOUNTAIN RED SOIL

通过33年施肥试验研究了不同施磷处理对山原红壤中磷素形态转化及含量的影响。结果表明,长期施用磷肥增加了红壤中全磷和速效磷的含量;施磷处理下土壤表层无机磷、有机磷显著积累。不同施肥处理下土壤无机磷组分均以Fe-P为主,占总量的50%左右;相关分析表明无机磷组分中的Fe-P、Al-P与速效磷分别呈极显著正相关(r=0.908)、显著正相关(r=0.706),表明Fe-P、Al-P为山原红壤的有效磷源。对于土壤有机磷而言,所有施肥处理的土壤中稳性有机磷比例最高,其次为中等活性有机磷,再次为高稳性有机磷,活性有机磷最低,前二者占有机磷总量的90%左右。有机磷组分与速效磷的相关性分析结果表明,中等活性有机磷、中稳性有机磷分别与土壤速效磷呈极显著正相关(r=0.861)、显著正相关(r=0.840)。说明中等活性有机磷和中稳性有机磷是土壤速效磷的主要来源。增施磷肥尤其是氮、磷、钾肥与农家肥配施后,可促进其他形态有机磷向有利于作物吸收的中等活性有机磷、中稳性有机磷转变。

Based on a long-term （33 years） fertilization experiment, changes in form and content of phosphorus in mountain red soil were investigated. Results show that the long-term P fertilization increased both Total P and readily available P in content in the soil, leading to significant accumulation of inorganic and organic P in the surface soil layer. In soils under P treatment inorganic fraction of P was composed mainly of Fe-P, which accounted for about 50%. Correlation analysis shows that readily available P was significantly related to Fe-P and Al-P with correlation coefficient being 0.908＊＊ and 0.706＊, respectively, which means that Fe-P and Al-P are the sources of readily available P in the soil. The results also show that Fe-P increased with phosphate fertilization, but Al-P reduced, which somewhat affected the content of soil available P. Soil organic P in the mountain red soil under long-term fertilization can sorted into four forms, that is, active organic P, moderately active organic P, moderately stable organic P and highly stable organic P. Soil organic P decreased somewhat in the soils without P fertilization and increased in the soils with P fertilization. In the soils with P fertilization the four soil organic P followed a decreasing order of moderately stable organic P 〉 moderately active organic P 〉 highly stable organic P 〉 active organic P, of which the first two accounted for 90% or so. Correlation analysis of organic fractions of P and readily available P shows that readily available P was significantly and positively related to moderately active organic P and moderately stable organic P, with correlation coefficient being 0.861＊＊ and 0.840＊, respectively, which demonstrates that moderately active organic P and moderately stable organic P are the major sources of readily available P in the soil. It was also found that a higher application rate of P coupled with N, K and barnyard manure can promote transformation of other forms of organic P into moderately active organic P and moderately stable organic P that are easily absorbed by crops.