Soil Phosphorus Available for Crops and Grasses Extracted with Three Soil-Test Methods in Southern Brazilian Soils Amended with Phosphate Rock

Abstract

The Mehlich 1 (M1) soil-test method has been used for soil phosphorus (P) extraction in southern Brazil. The objective of this work was to compare M1, Mehlich 3 (M3), and ionic exchange resin (resin) soil-test methods to evaluate the soil P available for crops and grasses in soils amended with phosphate rock (PR). Oxisol and Alfisol received triple superphosphate (TS) and PR. The M1 solution extracted greater P amounts in soils amended with PR compared with the M3 solution and resin methods. Lesser P amounts were extracted with the M3 solution. Crops yields were better associated with the P amounts extracted with M3 and resin methods in soils amended with PR. The results showed that M1 overestimates soil P availability to plants in soils amended with PR; the M3 solution best estimated the soil P available for crops and grasses in soils amended with PR.