Study On The Geographical Point Of Soil Phosphorus Equilibrium

Cultivated land resource is the foundation of mankind's survival, and study on sustainable cultivated land use is coming to be the focus of international research.. The renew-ability of cultivated land's productivity is the first standard to evaluate its use-system's sustainability. In this paper, some basses and methods are established for these evaluations by selecting proper index and using the geographical point of soil phosphorus equilibrium.The geographical point of soil phosphorus equilibrium refers to some quantitative characters of soil phosphorus system when its cycle becomes steady relatively in certain geographical, biological and climatic backgrounds. Its index and seeking method are determined differently in different studies. This paper chose Ca^-P as the index, based on its sensitiveness, stability, representatively and measurability: figured out the endogenesis geographical point of soil phosphorus equilibrium(of CK treat) as 3.2mg/kg, the exogenous geographical points of soil phosphorus equilibrium of-P, 1/2P (P2O5112.5kg/hm:) and complete P ( P2O5225kg/ hm2) as 3.6 mg/kg,8.6 mg/kg, and 14.2 mg/kg respectively.Using endogenesis and exogenous geographical points of soil phosphorus equilibrium as the two turning points in the S-type membership function, based on fuzzy mathematics, to evaluate the renewing status and fertility of Xiongxian country's soil phosphorus system. The results are that complete P treat is the best, CK and -P are in the lowest, 1/2P mediates. For the sustainable fertilization strategy, 1/2P is the best scheme, according to the evaluation of various treatments' exogenous renewing coefficient of soil phosphorus.