Method for digesting available nutrient from acid soil as well as combined digestion agent thereof

Abstract

The invention relates to a method for soaking and extracting available nutrient of acid soil and a combined extraction agent thereof. The combined extraction agent is a combination comprising NaOAc, Na2SO4, NaF, and EDTA. The combined extraction agent is prepared to aqueous solution which comprises 0.15mol / L to 0.25mol / L NaOAc, 0.02mol / L to 0.03mol / L Na2SO4, 0.01mol / L to 0.02mol / L NaF, 0.001mol / Lto 0.002mol / L EDTA and 0.06mol / L to 0.15mol / L H2SO4 and has a PH value between 2.4 and 2.6; then the solution with the mass ratio of the solution to soil between 3 and 20 is mixed to the soil which isto be measured; under the temperature condition between 20 DEG C and 30 DEG C, the solution is oscillated or stirred, soaked and extracted for 3 minutes to 20 minutes and filtered. The combined extraction agent of the invention has strong buffering performance, wide application range and high extraction efficiency, has remarkable positive correlation with a routine measuring result and has important significance to popularize balanced fertilization and improve the utilization rate of fertilizer.

Description

technical field [0001] The invention relates to the field of laboratory analysis, in particular to a method for extracting effective nutrients in acidic soil and a combined extraction agent thereof. Background technique [0002] Soil available nutrient content is the main basis for evaluating the nutrient supply capacity of the soil in the current season and making reasonable recommendations for fertilization. Obtaining a fast, accurate and well-correlated chemical method to extract soil nutrients to evaluate soil nutrient abundance and bioavailability is a prerequisite for soil testing to recommend fertilization or evaluate the allowable amount of soil harmful substances. Therefore, the analysis and testing of soil available nutrients has become the key content of soil fertilization and formulation of environmental protection measures. For the test of soil available nutrients, different types of soils usually use different soil extractants. Different extractants are used, ...

AI Technical Summary

Problems solved by technology

Some progress has been made in the research of combined extraction agents: the more famous ones are Morgan-Wolf reagent, Mehlic1 reagent, Soltanpour-Swab reagent and Mehlich3 reagent, etc. The earliest Morgan reagent (HOAC-NaAc, pH4.8) was obtained by Wolf Improved determination of various elements that can be used in acidic and neutral soils after adding DTPA; Mehlich1 reagent (HCl-H 2 SO 4 ) is only suitable for acidic sandy soil, and its application range is narrow; Soltanpour-Swab reagent (NH 4 HCO 3 -DTPA, pH 7.6) is suitable for alkaline and calcareous soils, but the reagent is unstable and the pH value is relatively too small; Mehlich3 reagent (HOAC-NH 4 NO 3 -HNO 3 -NH 4 F-EDTA, pH2.5) can be applied to the test of various elements in acidic and neutral soils, and can also be used in alkaline and calcareous soils, but this extraction agent cannot be applied to the extraction and determination of soil available nitrogen; Zhao Mengxia etc. have proposed No. II reagent (8.5%NaCl-0.05%NaF-0.0125mol / L HCl) that is applicable to acidic soil on the basis of summarizing previous studies, but this extraction agent has no effect on available nitrogen and available phosphorus in soil. , the extraction effect of available potassium is all bad, differs greatly with routine value, and average extraction rate is only 24.1%~34.9%, and needs to formulate different conversion coefficients to correct, and conversion error is bigger, and maximum can reach 57.1% ( Zhao Mengxia et al., Application of Combined Extraction Agent in Soil Rapid Measurement, Henan Agricultural Science, No. 6, 1998)

Disclosed a kind of combined extraction agent (NaHCO 3 -EDTA-NaF) and its extraction method, which are derived from the ASI method of the American International Agrochemical Service Company. The use of this method not only needs to be equipped with a series of valuable supporting facilities, but also needs to be used when the measurement results are applied. It is time-consuming and laborious to re-establish the abundance and deficiency index system, which greatly limits its popularization and application

The common disadvantage of the above-mentioned various formulations is that these extraction methods cannot be applied to low-cost rapid measurement, because it is difficult to eliminate the interference of various ions when performing colorimetry or turbidimetry; in addition, ammonium ions and nitric acid in some formulations The presence of root ions also makes it unsuitable for the determination of ammonium nitrogen and nitrate nitrogen. At the same time, ammonium ions also seriously interfere with the determination of potassium by tetraphenyl boron sodium method.

The present inventor once disclosed in CN 1502979A a combined leaching agent for acidic soil with a wide range of component contents, but follow-up research tests show that within the different content ranges of the leaching agents, the formed leaching agent The buffer capacity of the extraction system is very different, the amount of soil nutrients extracted by the extraction system is very different, and the degree of correlation with the conventional extraction method is different.

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