INTERPRETATION OF THE AVAILABLE PHOSPHORUS BY MEHLICH-1 AND MEHLICH-3 EXTRACTANT SOLUTONS IN SOILS OF THE RIO GRANDE DO SU STATE, BRAZIL

Multielement soil extractant solutions are used by several soil testing laboratories to determine the plant availability of several nutrients by the same extractant, to decrease costs and labor. The Mehlich-1 (M(1)) and Mehlich-3 (M(3)) solutions are often used for this purpose. In this study, they were used to evaluate soil P availability using 360 soil samples of the State of Rio Grande do Sul (Southern Brazil). The correlation coefficients between the P concentrations extracted by these solutions were strongly associated and highly significant. The P concentrations extracted by the M3 solution were on average 50 % higher than those extracted by M(1). The soil clay content affected the P extraction capacity of the M(3) solution, requiring an adjustment table for the interpretation of the P value by this method, as proposed here.