THE LANCASTER SOIL TEST METHOD AS AN ALTERNATIVE TO THE MEHLICH 3 SOIL TEST METHOD¹

Abstract

A study was conducted to compare and correlate the Mehlich 3 soil extraction method with the Lancaster soil extraction method. This study compared calcium (Ca), magnesium (Mg), potassium (K), and phosphorus (P) concentrations in 422 soil samples from eight fields, which varied greatly in soil type, texture, and fertility. Each soil sample consisted of 10 subsamples collected from 0 to 15 cm deep. Soil fertility was determined using both the Mehlich 3 soil test method and the Lancaster soil test method. Ca, Mg, K, and P extracted by the two methods were compared using linear regression. The Lancaster method consistently extracted higher concentrations of the nutrients than did the Mehlich 3 method for low soil Ca concentrations. As soil Ca increased, differences between the two methods diminished until a point was reached where the methods extracted equal amounts of the nutrients. After this point, the Mehlich 3 methods extracted more of the nutrients than did the Lancaster method. This was attributed to the neutralization of the acidity in the first stage of the Lancaster method. Despite these differences, good correlations were found between the two methods for Ca, Mg, and K, with R² for the regression equations ranging from 0.73 to 0.80. However, P levels were not highly correlated (R² = 0.39) between the two methods, indicating that estimates of this nutrient determined with one method were not comparable to estimates made with the other.