LIXIVIATION AND EXTRACTION OF ZINC IN A CALCAREOUS SOIL TREATED WITH ZINC-CHELATED FERTILIZERS

When Zn is added to calcareous soils to avoid Zn deficiencies, it can be fixed, if the source is a soluble inorganic salt, and leached, if i t is a stable complex. Relative mobilities of Zn-EDTA and Zn-lignosulf onate (LS) chelates added to calcareous soil columns as coated and unc oated fertilizers were determined. Zn-EDTA migrated and distributed th roughout the columns. About 51% of the Zn was leached with uncoated fe rtilizers but only about 10% when coated fertilizers were used. Zn-LS migrated very little, especially with coated fertilizers; the Zn remai ned mostly in the upper zone of the column and was not leached. The di stribution of the added Zn between different fractions of soil was det ermined by a sequential extraction procedure. When Zn-EDTA was added, the percentage of the most labile fractions increased slightly with re spect to the control soil throughout the entire profile of the column. Zn-LS displayed higher increases in the most labile fractions but onl y in the top layer of the column. Correlations between the extracted f ractions (P < 0.001%) showed that in general a dynamic equilibrium exi sted between them. DTPA-extractable Zn correlated (P < 0.001%) with th e two most labile fractions and to a lesser extent with the nonbioavai lable forms. Comparisons between coated and uncoated fertilizers show that the presence of coatings benefits Zn-EDTA fertilizers, decreasing the leaching and increasing the amount of biavailable Zn, but had no beneficial effect for Zn-LS fertilizers.