b Metodologias e eficiencia de extrator

Correlation studies were used to evaluate the extraction methodologies for micronutrients in soils of Paraná State, Brazil, aiming at the standardization of methods. The following were evaluated: Acid extractors (Mehlich 1), in a soil-to-extractor ratio of 1:5 and 1:10; an extractor composed of acid and complexing components (Mehlich 3), used in a 1:10 ratio; and a complexity extractant (DTPA), in 1:2. The Mehlich 1 and Mehlich 3 had two extraction forms: a) immediate filtration or after agitation; and b) filtration after decantation of 16 hours. Correlations were established between the contents in the soil and in corn plants. The highest levels of Zn and Cu occurred with the use of Mehlich 1 (1:10), with filtration after decantation, and Mehlich 3 (1:10), with both immediate filtration and filtration after decantation. For the Mn and Fe determinations, the standard methodology of the laboratories in Paraná, which uses Mehlich 1 with filtration after decantation, showed good correlation, while Cu determination found all extraction methodologies to be equivalent.