Soil testing and plant analysis in Brazil

Abstract

Soil testing in Brazil is done by about 180 laboratories, of which 167 provided the statistical information used in this paper. There are few differences in analytical procedures for the macronutrients and soil acidity. All laboratories determine exchangeable Ca, Mg, and K. Two thirds of the laboratories use Mehlich No. 1 solution to determine P whereas the other third extract the element from soils with an ion exchange resin procedure, introduced in Brazil in 1983. The pH is determined either in water or in 0.01 M CaCl₂. For lime requirement, the analytical data used is either exchangeable aluminum, SMP buffer pH, or cation exchange capacity and soil base saturation. Some laboratories determine also S, micronutrients, clay content, and electrical conductivity. Soil samples analyzed increased from 267 thousand in 1972 to 719 thousand in 1989. Private laboratories increased their share from 34% to 48% in this period. Sao Paulo State had the largest increase in the number of soil samples analyzed during the last decade, increasing from 65 thousand samples in 1982 to 255 thousand samples in 1989. Plant analysis is increasing in importance and about 40 laboratories analyzed around 100 thousand samples in 1991.