This study was conducted in a greenhouse with the purpose of comparing the efficiency of Mehlich-3, Mehlich-1, DTPA and AB-DTPA extractants in assessing Cu availability for maize and soybean. For the experiment with maize, 61 topsoil samples from different representative sites of São Paulo State were utilized, whereas for the soybean experiment 59 topsoil samples were employed. Nutrients were applied to the soil samples as follows: (i) in those with low Cu contents (<0.2 mg.dm-3 Cu as extracted by DTPA) two treatments were considered: complete, with all nutrients and Cu-enriched, using CuSO4, and no Cu-enrichment; and (ii) samples exhibiting Cu contents higher than 0.2 mg.dm-3 were not enriched with Cu. Considering all the samples, the AB-DTPA and Mehlich-3 methods showed more Cu extractability under maize, whereas under soybean the Cu extractability was higher for Mehlich-3. Very significant correlations between different methods were found, though correlation coefficients for all pairs of extractants were higher under maize. Taking into account both, Cu-enriched and no Cu-enriched treatments, the Mehlich-3 method was found to be more appropriate to explain the copper concentrations in the aerial part of maize and soybean.
soil analysis; availability; Mehlich-3; Mehlich-1; DTPA; AB-DTPA
