EFFICIENCY OF MULTINUTRIENT EXTRACTANTS FOR THE DETERMINATION OF AVAILABLE COPPER IN SOILS

Experiments under greenhouse conditions were carried out at the Instit ute Agronomico de Campinas in order to determine the efficiency of som e multinutrient extractants on the determination of available copper i n soils from the State of Sao Paulo, Brazil. These experiments employe d 31 soils using wheat and beans as test plants. All soil samples were limed to increase the soil pH to 6.0 and manured with copper-free fer tilizer. Copper was extracted from the soils before liming and before each planting using the Mehlich-1, Mehlich-3, or the TEA-DTPA as extra cting reagents followed by its determination using the inductively cou pled plasma emission spectrometry (ICP-AES) technique. The wheat and b eans plants were also analysed for their copper content. The results s howed that the extraction of the available copper decreased in the ord er: Mehlich-3, TEA-DTPA and Mehlich-1. The Mehlich-3 (R(2) = 0.80*) a nd the TEA-DTPA (R(2) = 0.74*) methods explained well the variation i n the copper concentration found in the aerial part of the wheat plant s, while the Mehlich-1 (R(2) = 0.45*) results were more appropriate t o explain the copper concentration found in the aerial part of the bea ns plants. Both multinutrient extractants, Mehlich-3 and TEA-DTPA, pro ved to be the best procedures in evaluating copper availability in the Brazilian soils selected.