Study On Rapid Measurement Of Soil Nutrients Suitable For Calcareous Soil

The abundance and deficiency of soil nutrients is an important basis for indicating soil fertility and guiding soil formula fertilization.However,the conventional laboratory analysis and testing methods have some disadvantages such as long consuming time and tedious testing steps,while the reaearch on the testing accuracy,the type of soil and the corresponding nutrient deficiency index suited for the rapid measurement method need to be strengthened.The popularization and application of precision fertilization technology in China should to be further prometed.In this paper,taking calcareous soil in the North China Plain as the tested soil sample and taking the routine laboratory analysis method as the reference method,the feasibility of rapidly determining soil available nutrients using rapid measuring instrument and M3 method was studied.Meanwhile,the improvement and optimization technology of the combined extractant was discussed in view of the shortcomings of the existing rapid measuring technology.Based on the analysis and evaluation of different testing methods,the more optimized method was developed,and the abundance and deficiency index of main nutrients suitable for soil rapid measurement technology were established.The major results were illustrated as follows:?1?The results of soil available phosphorus,available potassium,available iron,manganese,copper and zinc determinated by rapid measurement method had extremely significant correlationship with the results determinated by conventional method,and the correlation coefficients are 0.907^**?0.907^**?0.534^**?0.98^**?0.575^**.In this method,the fresh soil was directly measured in the field,the test speed was fast,the reagent preparation was convenient,and the price was in a reasonable range when the tested sample numbers were small.But the test accuracy was not high,and the variation of measured reaults was large.While when many trace elements needed to be measured and the sample numbers were large,the disadvantages such as the tedious operation procedure,the higher price,and the lower tested precision were found beecause of extracting and soaking each element with different extractant.?2?The results of available phosphorus,available potassium,available iron,manganese,copper and zinc determinated by M3 method had extremely significant correlationship with the results determinated by conventional laboratory method,and the correlation coefficients are 0.964^**?0.979^**?0.715^**?0.904^**?0.984^**?0.82^**.The above6 elements can be extracted by M3 using the same extractant at one time,with shorter oscillating time,higher testing efficiency and precision,and reasonable price.The M3method had obvious advantages in the simultaneous determination of a large number of samples and elements.?3?Because of the safety risk and difficulty in the storage and use of NH4NO3belonging to dangerous chemicals in M3 extractant,the study of M3A1 extractant using NH4Cl instead of NH4NO3,and using HCl instead of HNO3 was conducted.The results of soil available phosphorus,available potassium,available iron,manganese,copper and zinc were related extremely significant correlationship to the test results of conventional analysis methods in the laboratory,and the correlation coefficients are 0.953^**?0.989^**?0.414^*?0.412^*?0.978^**?0.968^**.?4?In view of the low pH of M3 and M3A1 extractant,which led to the high determination results,the HCl was removed from the M3A1 extractant and the improved M3A2 method was studied.The results of the above six elements determinated by M3A2also had the significant relationship with the ones determinated by the conventional analysis method,and the correlation coefficients are 0.981^**?0.992^**?0.517^**?0.639^**?0.977^**?0.962^**.Compared with M3A1 method,the composition of M3A2 extractant was simpler,the oscillation time was not changed,the test accuracy and the test efficiency were higher.In addition,the measured value of M3A2 method was significantly higher than the value of conventional measurement method,which was more convenient for the classification of nutrient level and the recommendation of fertilization.To sum up,the rapid measuring method and M3 method were both suited for measuring available nutrients of calcareous soil in the North China Plain.According to the fitted equation,the nutrients abundance and deficiency indexes suitable for the rapid measurement methods were established.But the two methods had their own merits and demerits,and their application scope was different.The improved M3A1 method based on M3 and the M3A2 method that was improved on the basis of M3A1 had shown obvious advantages.Therefore,M3A2 method was the more ideal method for simultaneous determination of multielement nutrients at the same time.