INFLUENCE OF SULFUR AND NITROGEN-FERTILIZER ON THE UPTAKE OF IRON, MANGANESE, AND ZINC BY CORN PLANTS GROWN IN CALCAREOUS SOIL

A pot experiment was conducted with a coarse-textured calcareous soil (pH-H2O 8.3) to study the effect of single and combined application of N and S fertilizers on soil pH, Fe, Mn, Zn, and P mobilization, and on growth and micronutrient uptake by com (Zea mays L.). Increasing amounts of elemental sulfur were mixed with the soil. To stimulate S oxidation, the treated soils were incubated for six weeks at field capacity. Nitrogen was applied as NH4NO3 (100, 200, and 400 mg N/kg). After six weeks, dry matter yields were recorded and shoots were analyzed for Fe, Mn, Zn, and P. At the end of the experiment, soil pH and the DTPA-extractable micronutrients were determined. The results showed that: a. Soil pH was decreased by 0.2, 0.5, and 0.9 unit as a result of increasing S applications. b. Applied sulfur and N fertilizer had increased the availability of micronutrients to following crops. c. Application of N and/or S resulted in increased dry matter yields. d. Manganese uptake tended to be higher as amounts of N applied increased; this was most evident at the higher S application rates. This effect was, however, reversed for Fe, Zn, and P uptake. e. Under our experimental conditions, promising results were achieved on improving micronutrient availability and uptake when 400 mg N/kg was combined with 3 g S/kg.