Comparison Study On The Methods For Determination Of Available N,P And The Organic Matter In Forest Soil

The forest soil's type was extremely complex, the shape and quantity of available nutrient had a distinct difference in different soil.Recently in China, The comparable studied of the method for determination on soil available N, P and the soil organic substance limited at agrology, in contrary, the study about acidic forest soil was rare and so was in the diversity of the different kinds of soil by classical methods. The comparison of the methods for determination about soil available N, P and the soil organic substance in the dark brown forest soil were studied synthetically in the thesis. The method for determination of soil available N was studied:: compare alkali-hydrolyzable diffusion method by used reductant or not, and so the study of the method for determination of soil available P: compare 0.05mol/LHCl 0.025mol/LH₂SO₄, 0.03mol/L NH₄F - 0.025 mol/L HCl and 0.5mol/LNaHCO₃ extraction method, fractionation of inorganic soil P method put forward by Zhang shoujing and Jackson, fractionation of inorganic soil P used in the calcareous soil put forward by Gu yichu and Jiang bofan. The study of the method for determination of soil organic matter was done: compare potassium dichromate method, microwave method, hydration heat method, digestion and burning digestion method. The results showed that:In the method for determination of soil available N: the methods used reductant or not both were suitable for the dark brown forest soil, but the methods no reductant were more accurate than that used. There was significant correlation between soil available N determined no reductant and diffused time. The correlation coefficient between soil available N no reductant and diffused time were better than that between soil available N with reductant and diffused time. So it suggested that the determined methods no reductant should be popular with the dark brown forest soil.In the method for determination of soil available P: 0.05mol/LHCl-0.025mol/L H₂SO₄ and 0.5mol/LNaHCO₃ extraction methods were both suitable for the dark brown forest soil, as to 0.5mol/LNaHCO₃ decolorization, KMnO₄ decolored method were more accurate than activated carbon decolored method and KMnO₄ decolored method was more suitable than activated carbon decolored method in the dark brown forest soil. In the fractionation of inorganic soil P method â…  and â…¡ , background decolored method of fractionation of inorganic soil P method â…¡ were more accurate than other methods, there were significant correlation between the contents of Al-P, Ca₂-P, Ca₁₀-P, Ca-P respectively determined by background decolored method of inorganic soil P method II and activated carbon decolored method of inorganic soil P method â…  .By analyzing the correlation by the fractionation of inorganic soil P mothed â…  , â…¡ and 0.5mol/L NaHCO₃ extraction methods, there were significant correlation between thecontents of Ca2-^ Al-P> Fe-P, Cag-P respetively determined by background decolored method of the fractionation of inorganic soil P mothed II and that 0.5mol/LNaHCO3 extraction methods. Activated carbon decolored method of fractionation of inorganic soil P method I and background decolored method of fractionation of inorganic soil P method II were adaptable for the dark brown forest soil.By comparing and analyzing the correlation all determined methods of soil organic matter, there were significant correlation among all determined methods, the results showed that five methods were all suitable for the dark brown forest soil, but burning digestion method and microwave method were more accurate than other methods. The partial correlation analysis between all determined methods of soil organic matter and the content of total N> P showed that correlation between methods of soil organic matter and the content of total N were more closed than correlation between methods of soil organic matter and the content of total P. By analyzing partial regression coefficient, correlation between potassium dichromate method and burning digestion method were more closed than that between potassium dichromate method and microwave method. Burning digestion method was ch^ap and no pollutant, so when determining soil organic matter, the preferred method was burning digestion .