Comparison of soil tests to determine micronutrients status in Argentina soils

Soil extraction techniques to measure the status of available micronutrients for plants are important in the diagnosis of deficiency or toxicity. Mehlich 3 (M3), EDTA (pH = 8.2), DTPA-TEA, and Soltanpour and Schwab (SS) solutions were confronted for their ability to extract simultaneously copper (Cu), zinc (Zn), manganese (Mn), and iron(Fe). Argentinean soils from different taxonomic orders with widely varying properties were investigated. The values obtained showed that DTPA-TEA and SS solutions extracted similar amounts of Zn, Fe, and Mn, while EDTA dissolved comparatively higher amounts of Fe and Mn. Mehlich 3 yielded the highest extractions for the four micronutrients. Soil pH not only affected the extraction of Mn by DTPA-TEA, SS, and EDTA extractions, but also the extraction of Fe by EDTA. The organic carbon affected the determination of Fe and Zn in all cases. The correlations of the different tests for Cu, Zn, Mn, and Fe were significant. The results suggest that for the determination of the bioavailable status of micronutrients, any of the studied tests could be applied using the soil edaphic properties as factors to improve the correlations between them and standardize the methods.