Liming and chemical extractants of manganese and zinc in cerrado Habludox and Quartzpsament planted with soybeans

Abstract

Low micronutrient levels, particularly of manganese and zinc, are frequently found to limit crop growth and yield in cerrado soils. Their availability can be further more reduced by soil liming. It is desirable therefore to ascertain chemical extractant or extractants, capable of assessing the available levels of both manganese and zinc for soybeans as influenced by lime application. A pot experiment was carried out using a Habludox (LV) and a Quartzpsament (NQ), and two soybeans cultivars (IAC 5- and IAC 7). Base saturation (V %) was raised to 60 by the addition of either CaCO3, CaCO3 + MgCO3 (3+) or CaCO3 + MgCO3 (+). Rates of Mn and Zn were 25 and 5 mg dm-3 for LV and 0 and 3 for NQ, respectively. Soil Mn was evaluated as “exchangeable” (Mehlich , Mehlich 3 and DTPA-TEA), water soluble, easily reducible and total; Zn was determined after extraction with Mehlich , Mehlich 3 and DTPA-TEA. There was a high correlation, both for Mn and Zn, among the three extracting solution. Significant and positive correlations were also found between the values given by these extractants and leaf Mn and Zn levels, although in the NQ soil only the Mn extracted by Mehlich 3 correlated positive and significantly with the level of Mn found in the leaves of the IAC 7 cultivar.Additional keywords: cerrado; Glycine max; plant nutrition; soil fertility.