Evolution Trend of Soil Available N, P and K Contents in Xinmin District

A detailed survey was made for soil available nitrogen, phosphorus and potassium in agricultural fields and sheltered grounds in Xinmin District, and a comparative study on the evolutionary trend of soil available P and K was made on the basis of the survey of soil nutrients in 1980. As for agricultural fields, the average content of available nitrogen was 98.96mg/kg in 2008; the average content of available soil phosphorus has increased gradually from 4.96mg/kg in 1980 to 11.61mg/kg in 2008; a gradually decrease of available soil potassium was shown with a rate of about 1.90% per year from 128.08mg/kg in 1980 to 79.90mg/kg in 2008. As for sheltered grounds, the longer the sheltered ground was utilized,the higher the content of available N, P and K.