In accordance with the requirements of the "Notice of the State Council on Carrying out the Third National Soil Census" and the national unified technical route determined by the "Third National Soil Census Work Plan" (Nongjianfa [2022] No. 1), provinces, autonomous regions, and municipalities directly under the central government have begun 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, testing laboratories are determined through screening, and provincial quality control laboratories and national quality control laboratories are determined through confirmation, and they each bear different responsibilities and tasks.

Testing laboratories must prepare, preserve, transfer and test samples in accordance with the requirements of the "Technical Specifications for the Preparation, Storage, Circulation and Testing of Soil Samples in the Third National Soil Survey (Trial)" and the soil survey sample testing task arrangements of the provincial third soil survey leading group office. This article specifically extracts Part 5: Sample Testing of the "Technical Specifications for the Preparation, Storage, Circulation and Testing of Soil Samples in the Third National Soil Survey (Draft for Comments)" for reference by relevant testing laboratories.

5. Sample testing

The agricultural and rural departments of each province (autonomous region, municipality) are responsible for determining the quality control laboratories and testing laboratories that undertake the task in their region and organizing the sample testing work. The testing laboratories that undertake the task should carry out soil sample testing work under the guidance of the quality control laboratory in accordance with the requirements of the testing task and the prescribed technical methods, and report the test results on time.

5.1 Testing plan

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

5.2 Detection Methods

The testing laboratory carries out testing work in strict accordance with the technical methods specified below .

5.2.9 Cation exchange capacity

5.2.9.1 Ammonium acetate exchange - volumetric method (acidic and neutral soils): Determination of cation exchange capacity and exchangeable base of neutral soils (NY/T 295-1995).

5.2.9.2 Calcium acetate exchange - volumetric method (calcareous soil): "Soil Testing Part 5: Determination of Cation Exchange Capacity of Calcareous Soils" (NY/T 1121.5-2006 ).

5.2.9.3 EDTA-ammonium acetate exchange-volumetric method: "Soil Analysis Technical Specifications" Second Edition, 12.1 EDTA-ammonium acetate exchange method.

5.2.9.4 Ammonium acetate exchange-volumetric method (acidic and neutral forest soils): Determination of cation exchange capacity of forest soils (LY/T 1243-1999).

5.2.9.5 Ammonium chloride-ammonium acetate exchange-volume method (calcareous forest soil): Determination of cation exchange capacity of forest soil (LY/T 1243-1999).

5.2.13 Organic matter

5.2.13.1 Potassium dichromate oxidation-volumetric method: Appendix C (Normative Appendix) Determination of soil organic matter in "Quality Grades of Cultivated Land " (GB/T 33469-2016).

5.2.13.2 Potassium dichromate oxidation-external heating method: "Determination of organic matter in forest soil and calculation of carbon-nitrogen ratio" (LY/T 1237-1999).

Automatic soil organic matter detection solution:

Download the full text: Research report on the development of a fully automatic detection method for soil organic matter

Automatic detection scheme of soil cation exchange capacity:

Download the full text: Validation report of the fully automatic detection method of soil cation exchange capacity