A: Mehlich3(M3) is a combined extractant suitable for neutral and acidic soils, which was proposed by Dr. Mehlich of North Carolina State University in 1982 according to the actual situation in the United States. It can analyze phosphorus, potassium, calcium, magnesium, sodium, iron, manganese, copper, zinc, boron, chromium and cadmium in soil. As far as the determination principle is concerned, M3 extractant has the following characteristics compared with conventional extractants of other elements:

First, it contains NH4F, and the extraction principle is similar to BRAY1;

Second, it is better than Mehlich1in extracting available phosphorus from neutral and alkaline soils;

Third, it has a good correlation with the nutrient absorption of crops in most soils, which can reflect the supply capacity of soil available nutrients;

Fourth, the determination efficiency is high, which is convenient for automation (such as simultaneous determination of multiple elements by ICP). Therefore, M3 has advantages that the first two extractants do not have. Once introduced, it is expected to become a multi-element extractant suitable for different soil types.