Degradation of soil nutrients in Southeast China.

A total of 2 190 soil nutrient data in the Second National Soil Survey of China were collected to assess thedegradation of soil nutrients in the hilly region of Southeast China. The definition of soil nutrient degradationis suggested firstly then the evaluation criteria are set up and the current status of degradation of red soil and latosol is assessed. The percentages of areas in four grades of soil nutrient degradation, i.e., slightlydeficient, medium deficient, severely deficient and extremely deficient, were 21.3%, 43.3%, 16.2% and 3.0%for soil total N; 0.7%, 6.4%, 16.7% and 76.2% for soil available P; and 25.4%, 26.3%, 8.6% and 5.0% forsoil available K, respectively. The severity of soil nutrient degradation was in the order of P N K. Themajor factors leading to the degradation of soil nutrients in quantity include soil erosion, leaching and theconsumption by crops. And the principal faCtor affecting the degradation of soil nutrieots in availability isthe fixation of N, P and K, especially the fixation of phosphorus. The average amouat of P fixed by soils is408 mg kg-1, and upland soils can fix more P than paddy soils.