Method for digesting available nutrient from neutral and calcareous soil as well as combined digestion agent thereof

Abstract

The invention relates to a method for soaking and extracting available nutrient of neutral soil and calcareous soil and a combined extraction agent thereof. The combined extraction agent is a combination consisting of NaHCO33, Na2CO3 and Na2SO4; the combined extraction agent is prepared to aqueous solution which comprises 0.40mol / L to 0.50 mol / L NaHCO3, 0.020 mol / L to 0.030mol / L Na2CO3 and 0.30 mol / L to 0.40mol / L Na2SO4 and has a PH value between 8.4 and 8.6, then the solution with the mass ratio of the solution to soil between 5:1 and 25:1 is mixed to the soil which is to be measured; under the temperature condition between 20 DEG C and 30 DEG C, the solution is oscillated or stirred, soaked and extracted for 4 minutes to 20 minutes and filtered. The extraction agent has large buffering capacity and wide application range and can rapidly and high-efficiently soak and extract ammonium nitrogen, nitrate nitrogen, available phosphorus, rapidly available potassium for one time and has high extraction efficiency and remarkable relativity with a routine measuring result and satisfies the needs of rapidly measuring the main available nutrient in the soil.

Description

technical field [0001] The invention relates to the field of laboratory analysis, in particular to a method for extracting effective nutrients in neutral and calcareous soils and a combined extraction agent thereof. Background technique [0002] For the test of soil available nutrients, different soil extractants are usually used for different types of soil, and the measured nutrient content varies greatly due to the different extractants used. Selecting an appropriate soil extractant is the prerequisite for accurate determination of available nutrients. The research and application of soil extraction agents in our country is relatively backward, and the traditional method during the second soil survey period is still widely used at present. Each effective nutrient uses a special extraction agent, which takes a long time, complicated operation, and labor-intensive. , Time-consuming, expensive medicines, very low efficiency. One of the ways to solve it is to realize the join...

AI Technical Summary

Problems solved by technology

The earliest Morgan reagent (HOAC-NaOAc, pH4.8) can be used for the determination of various elements in acidic and neutral soils after being improved by Wolf and 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 available nitrogen in soil; In recent years, Chen Tongbin et al. proposed SB / D (NaHCO 3 -DTPA) reagent, but it needs to be used in conjunction with an expensive ICP spectrometer, and is not suitable for colorimetric and rapid measurement systems, and its application range is greatly limited; Zhao Mengxia et al. proposed a method suitable for neutral, No. 1 extraction agent for calcareous soil (5% Na 2 SO 4 -3.5% NaHCO 3 ), and this extraction agent has a poor effect on the extraction of available nitrogen in the soil, which is very different from the conventional value: the average extraction rate of available nitrogen (that is, the percentage of the rapid measurement value in the conventional value) is only 52.5% to 68.2% (Zhao Mengxia etc., the application of combined extracting agent in soil rapid measurement, Henan Agricultural Science, the 6th period of 1998); Disclosed a kind of combined extracting 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. Re-establish the index system of abundance and deficiency, these reasons greatly limit its popularization and application

The common disadvantages of the above-mentioned various formulations are: these extraction methods cannot be applied to low-cost colorimetric rapid measurement, because it is difficult to eliminate the interference of various ions when performing colorimetry or turbidimetry; in addition, ammonium ions in some formulations And the presence of nitrate ions also makes it impossible to apply to the determination of ammonium nitrogen and nitrate nitrogen, and ammonium ions also seriously interfere with the subsequent determination of potassium by the sodium tetraphenylborate method.

The present inventor once disclosed a kind of combined extraction agent (NaHCO 3 -Na 2 CO 3 -Na 2 SO 4 -NaOAc), but this kind of leaching agent containing NaOAc does not match with the follow-up rapid measurement colorimetric reaction system, especially when measuring available phosphorus, the pH value of the solution is unstable, resulting in unstable color reaction and the accuracy of the measurement results. Difficult to guarantee

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