Soil Testing and Fertilizers
The Mehlich 1 and 3 soil test extractants are the most widely used in laboratories of the southern United States today. Tennessee began using the Mehlich 1 extractant in December, 1981. Existing soil test calibration data in Tennessee are based on the Mehlich 1 soil test extractant,1,2 which became available in 1953.
"W229-Interpreting Mehlich 1 and 3 Soil Test Extractant Results for P and K in Tennessee," The University of Tennessee Agricultural Extension Service, W229 08/09 10-0043, https://trace.tennessee.edu/utk_agexcrop/63