不同初始pH值酸性土壤净矿化、净硝化和酸度变化分析

采集了4个不同初始pH值酸性土壤,在60%土壤持水量和25 ℃条件下对土壤矿化、净硝化和酸度变化进行了研究.结果表明,Ⅰ号土壤(pH=4.03,茶园土)矿化作用不明显,Ⅱ号(pH=4.81,玉米地)、Ⅳ号(pH=6.02,菜地)土壤矿化模式为Logistic 方程,Ⅲ号土壤(pH=5.41,菜地)为指数方程.不加NH+4条件下Ⅱ、Ⅲ、Ⅳ号土壤净硝化模式为一级反应方程,加NH+4后净硝化速率增加一个数量级.培养结束后不加NH+4条件下Ⅱ、Ⅲ、Ⅳ号土壤pH值没有变化,加NH+4处理后pH值显著降低,同时交换性Al3+显著增加.加NH+4促进酸性土壤(pH=4.81~6.02)硝化和酸化,但pH值过低的土壤(pH=4.03)NO-3-N、pH值和交换性Al3+无显著变化.

An analysis on the changes of net mineralization,net nitrification and acidification of acid soil with different initial pH values

A laboratory soil incubation condition with moisture content 60% WHC and temperature at 25 ℃ was conducted to study dynamics of net mineralization,nitrification and acidification of four acidic agricultural soils with different initial pH,which were collected from a tea garden and three cropland in Yunnan province.The results showed that the mode of time courses for NH+4-N+NO-3-N accumulation followed a logistic model for soil II(pH 4.81,corn field) and Ⅳ(pH 6.02,vegetable field),exponential model for soil Ⅲ(pH 5.41,vegetable field).No significant mineralization was found for soil Ⅰ(pH 4.03,tea garden field).NO-3-N accumulation in the soil followed a first-order reaction model for soil Ⅱ,Ⅲ and Ⅳ without additional NH+4,and an addition of NH+4 stimulated the soil nitrification significantly.By inputting NH+4 ,initial pH of Ⅱ,Ⅲ and Ⅳ soil was significantly changed,resulting in a decrease in soil pH and an increase in soil exchangeable Al3+ content,which did not happen in soil I with or without NH+4-input.The results indicated that for some soil with a very low pH,such as pH 4.03,nitrification,pH and exchangeable Al3+ were not affected by the available NH+4.