Survey and Study on Soil Nutrients of Different Cropping Systems in Northern Ecology Region of Tianjin

By fertilizer survey and soil collection,the contents of soil nutrients and changes of farmland and greenhouse were studied in the northern ecological region in Tianjin.The results showed that the contents of soil organic matter and soil total nitrogen in 2007 increased as compared with the ones in 1982,increased by 35.2% and 30.5%.The contents of soil available phosphorus and soil available potassium in 2007 increased by 652.1% and 29.2%,respectively,as compared with the ones in 1982.The contents of soil nutrients in greenhouse were higher than the ones in farmland.The increase in soil nutrient was correlation with fertilizer application level in farmland.This research advanced some references for scientifically applying fertilizers in farmland.