Effect of Soil: Bray no. 1 Ratios on the Amount of Phosphorus Extracted from Calcareous Minnesota Soils

Abstract A field study was conducted to determine extractable phosphorus variability on highly fertilized calcareous soils when three different ratios (1:10, 1:50, and 1:100) of soil to Bray no. 1 extracting solution were used. Calcium carbonate equivalence (CCE) was determined on all samples and calcite/dolomite fractions were determined on randomly selected samples. On the soils where calcitic carbonates predominated, an inverse relationship was found between the amount of P extracted by the three ratios and the CCE. This relationship, however, was not as marked when the ratio of soil to Bray no. 1 extractant was increased to 1:50 and 1:100. On the dolomitic samples, an inverse relationship was also found between the P extracted by the 1:10 and 1:50 ratios and the CCE; however, no such relationship was noted when the 1:100 ratio was used. In general, the variability of the extractable P was greatly reduced in all samples when the wider ratios of soil to extractant were used. This investigation would indicate that available soil P from highly fertilized calcareous fields could be determined more accurately by using wider ratios of soil to Bray no. 1 extractant.