A Soil Test for Phosphorus Based Upon Fractionation of Soil Phosphorus: II. Development of the Soil Test

Abstract The correlation of soil P fractions with P uptake by millet was used as a basis for developing a soil test. The soil test consists of shaking 1 g. of soil with 20 ml. of solution made up from 17 ml. of 0.3 N NaOH and 3 ml. of 0.5 N Na 2 C 2 O 4 . The shaking time had little effect on the amount extracted. The soil test works particularly well on soils of pH above 7.