Focusing on the third national soil census, the automatic detection plan for organic matter and cation exchange capacity was introduced

In accordance with the requirements of the "Notice of the State Council on Launching the Third National Soil Census" and the national unified technical route determined in the "Work Plan for the Third National Soil Census" (Nong Jian Fa [2022] No. 1), all provinces, autonomous regions, municipalities directly under the Central Government, etc. Began to organize the screening of soil census laboratories. The third national soil census laboratories are divided into three categories: testing laboratories, provincial quality control laboratories and national quality control laboratories. Among them, the testing laboratory is determined through screening, the provincial quality control laboratory and the national quality control laboratory are determined through confirmation, and they undertake different responsibilities and tasks respectively.

The testing laboratory shall prepare the samples according to the requirements of the "Technical Specifications for Preparation, Preservation, Circulation and Testing of Soil Samples for the Third National Soil Census (Trial)" and the task arrangements for soil census samples of the Provincial Leading Group Office of the Third Soil Census. Preparation, preservation, circulation and detection work. This article excerpts Part 5: Sample Testing of the Technical Specifications for Soil Sample Preparation, Preservation, Circulation and Testing for the Third National Soil Census (Draft for Comment) for reference by relevant testing laboratories.

5Sample detection

The agricultural and rural departments of all provinces (autonomous regions and municipalities) are responsible for determining the quality control laboratories and testing laboratories in their respective regions, and organizing sample testing. The testing laboratory undertaking the task shall carry out soil sample testing work under the guidance of the quality control laboratory in accordance with the testing task requirements and prescribed technical methods, and submit the testing results on time.

5.1 Test plan

The provincial-level soil three general work leading group office is responsible for coordinating the soil sample testing in the region and formulating a sample testing plan. The sample testing plan should include sample testing indicators, testing methods, quality control requirements, testing data reporting requirements, etc.

5.2 Detection method

The testing laboratory conducts testing in strict accordance with the technical methods specified below .

5.2.9 Cation exchange capacity Ammonium acetate exchange - volumetric method (acidic, neutral soil): "Determination of cation exchange capacity and exchangeable base in neutral soil" (NY/T 295-1995). Calcium acetate exchange-volume method (calcareous soil): "Soil Testing Part 5: Determination of Cation Exchange Capacity in Calcareous Soil" (NY/T 1121.5-2006 ). EDTA - Ammonium Acetate Exchange - Volumetric Method: "Technical Specifications for Soil Analysis" Second Edition, 12.1 EDTA - Ammonium Acetate Exchange Method. Ammonium acetate exchange-volume method (acidic, neutral forest soil): "Determination of Cation Exchange Capacity in Forest Soil" (LY/T 1243-1999). Ammonium chloride-ammonium acetate exchange-volume method (lime forest soil): "Determination of cation exchange capacity in forest soil" (LY/T 1243-1999).

5.2.13 Organic matter Potassium dichromate oxidation-volume method: Determination of soil organic matter in Appendix C (normative appendix) of "Cultivated Land Quality Grades" (GB/T 33469-2016). Potassium dichromate oxidation-external heating method: Determination of Forest Soil Organic Matter and Calculation of Carbon-Nitrogen Ratio (LY/T 1237-1999).

Soil organic matter automatic detection scheme:


Full text download: Report on the development of an automatic detection method for soil organic matter

Soil cation exchange capacity automatic detection scheme:


Full text download: Validation report of automatic detection method of soil cation exchange capacity


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