Soil testing is the precondition of quantitative fertilization.To test the contents of soil available nutrients needs investments,and there are many errors when converting the tested values into soil nutrient application.Therefore,it is very significant on theory and practice to study principles and models of the semi-quantitative fertilization under the condition of no soil testing.The research results showed that ecological balanced fertilization model can be used as a semi-quantitative fertilization model.It has many strongpoints,such as complete functions,plenty of information,less parameter variations,easy for obtaining parameters,and precise in calculation,etc.
[Objective] The aim was to reveal changes of soil organic matter fraction and their corresponding carbon management indexes as affected by different land use types.[Method]Soil organic carbon,active soil organic carbon and soil carbon management index（CMI）of different land use types in Guilin Maocun karst area were studied.Sampling with field investigation and laboratory testing was carried out.Heavy potassium chromate method was adopted to determine soil organic matter.333 mmol/L KMnO4 oxidation method was used to determine active organic carbon.[Result]With active soil organic matter increasing,the differences of CMI between different land use types were bigger.The CMI value of different land uses was shrubforest paddy fielddry farmland.The statistical analysis showed that labile organic matter was related with major soil properties at a significant level.[Conclusion]Labile organic matter could be used to reveal the influence of different land use types on soil organic matter and carbon management index in karst area.
