Comparative Study On Methods For Measuring Trace Element In Chongqing Soil

Measured soil and fertilizer assignment is arduously.Measuring soil is a foundation work.For the mensuration of trace element, simple and accurate method is extremely essential. Among the methods of trace element mensuration, conventional method,Mehlich3 (called M3 for short) and Agro Services International Inc method (called ASI for short). The conventional method has proved be a good method by a lot of experiments in lab and biologic test and applies in many domain.But,its localization is show in complex operation and mensurating batch samples.The M3 method and the ASI method can also use in extracting P,K.The operations of the two methods are more simple than conventional method. The most important aspect is applicability in south mountainous region soil. At present,there is few report about applicability on the soil.Therefore, these three methods are suitable or not need the biologic test to approve.This experiment uses the standard bioassary method.Contrasting absorptive amount of trace elements (Cu,Zn,Fe,Mn) and measured value of the three methods through the wheatpot cultivate, selects one method which is both to be suitable and accurate for soil in south. Meanwhile, the differences of M3 method, ASI method and conventional method are analysed by correlation analysis.The experiment obtains the results below:(1)The M3 extraction value is the highest one of the three methods as a whole,next is ASI value, conventional method value is the lowest.(2)Chemic methods compare with the bioassary methodCu: The related coefficient of conventional method, M3 method and ASI method are 0.715^**(n=18), 0.563^**(n=21), 0.538^**(n=21) respectively,namely R_conventional＞R_M3＞R_ASI;Zn: The related coefficient of conventional method, M3 method and ASI method are 0.597^**(n=21), 0.496^* (n=21), 0.421^* (n=21)respectively,namely R_conventional＞R_M3＞R_ASI;Fe: The related coefficient of conventional method, M3 method and ASI method are not significant correlation.Mn: The related coefficient of conventional method, M3 method and ASI method are 0.757^**(n=19),-0.487 (n=21), 0.898^** (n=19) respectively,namely R_ASI＞R_conventional＞R_M3;The relativity of bioassary method with conventional value in Cu,Zn,Mn is extremely remarkable.These Cu,Zn,Mn can be viewed as available part. The Cu measured value of bioassary method and M3 method are significant correlation. The Cu,Mn measured value of bioassary method and ASI method are significant correlation.For Mn,M3 measured value and bioassary method are negative correlation,so M3 measured value can not be available part.(3) In acidic soil (n=24), related coefficients of conventional method and bioassary method are R_Cu=0.634^**, R_Zn=0.685^**, R_Mn=0.309 respectively;M3 method and bioassary method are R_Cu=0.579^**, R_Zn=0.368, R_Mn=-0.218 respectively;ASI method and bioassary method are R_Cu=0.437^*, R_Zn=0.416^*, R_Mn=0.520^**respectively.In neutral and calcareous soil (n=18), related coefficients of conventional method and bioassary method are R_Cu=0.741^**, R_Zn=0.550^**, R_Mn=0.547^* respectively;M3 method and bioassary method are R_Cu=0.522^**, R_Zn=0.334, R_Mn=0.323 respectively;ASI method and bioassary method are R_Cu=0.601^**, R_Zn=-0.461, R_Mn=0.455^* respectively.According to the relativity, Ingredient in jointly extractant and its consistency determined the element form and quantity.Strong acid extractant don't fit for available nutrient in south neutral and calcareous soil of mountainous region.(4) In each kind of fertilizer processing, relativity of bioassary method with conventional method or ASI method are consistent.(5) For the three chemic methods,ASI method and conventional method on measuring Cu,Zn,Fe,Mn in soil are related coefficient.The related coefficients are R_Cu=0.897^** (n=21), R_Zn= 0.860^**(n=21), R_Fe=0.696^**(n=21), R_Mn=0.963^**(n=20); M3 method and conventional method on measuring Cu,Zn,Fe in soil are related coefficient.The related coefficients are R_Cu= 0.705^** (n=18), R_Zn=0.537^** (n=21), R_Fe=0.704^** (n=21).Through t value inspection, numerical value of Cu in the four elements measured by the three chemic methods are not differently remarkable.In brief, the related coefficient of conventional measured value and bioassary method value are remarkable in Cu,Zn,Fe.This can reflect requirement of crop,so conventional measured value may be available nutrient in soil.The related coefficient of M3 value and bioassary method value are not remarkable,which can't meet experiment demand.Meanwhile, the colour of extracting solution will interfere with P. Therefore,M3 method need further research.The measured value of ASI method and conventional method are interrelated remarkable,and ASI value is aslo interrelated remarkable with bioassary method,so it can be used as reference value in measuring available nutrient. Fe measured value can't be applied in measuring soil because of related coefficients that bioassary method and the three chemic method are not remarkble at all. The main reason is that Fe accumulates on superficial of root system and measuring value can't represent absorptive amount.Thereby, the standard system of Fe measuring method need change in future.