COMPARISON OF SOIL TESTS TO DETERMINE MICRONUTRIENTS STATUS IN ARGENTINA SOILS

Soil extraction techniques to measure the status of available micronut rients for plants are important in the diagnosis of deficiency or toxi city. Mehlich 3 (M3), EDTA (pH = 8.2), DTPA-TEA, and Soltanpour and Sc hwab (SS) solutions were confronted for their ability to extract simul taneously copper (Cu), zinc (Zn), manganese (Mn), and iron(Fe). Argent inean soils from different taxonomic orders with widely varying proper ties were investigated. The values obtained showed that DTPA-TEA and S S solutions extracted similar amounts of Zn, Fe, and Mn, while EDTA di ssolved comparatively higher amounts of Fe and Mn. Mehlich 3 yielded t he highest extractions for the four micronutrients. Soil pH not only a ffected the extraction of Mn by DTPA-TEA, SS, and EDTA extractions, bu t also the extraction of Fe by EDTA. The organic carbon affected the d etermination of Fe and Zn in all cases. The correlations of the differ ent tests for Cu, Zn, Mn, and Fe were significant. The results suggest that for the determination of the bioavailable status of micronutrien ts, any of the studied tests could be applied using the soil edaphic p roperties as factors to improve the correlations between them and stan dardize the methods.