The effect of iron chelate and sulfur amendments on soil microbial activity

Abstract

Agricultural practices in the Maltese islands use both iron chelate and sulfur fertilisers to correct iron chlorosis and to provide plants with micronutrients. Some soil studies regarding microbial activity with the addition of these fertilisers have been made, even on calcareous soil, but none have been conducted on soils found in Malta. For this experiment FeEDDHA with 6% water-soluble Fe was used for the iron chelate fertiliser, and elemental sulfur was used for the sulfur fertiliser. Four set of experiments with three different fertiliser concentration for each fertiliser were conducted over a time frame of eight weeks, and were read a total of four times. Elemental sulfur concentration were 3g S/Kg, 6g S/Kg and 12g S/Kg soil, and FeEDDHA concentrations were 0.01g FeEDDHA/Kg, 0.213g FeEDDHA/Kg and 0.953g FeEDDHA/Kg soil. Microbial activity was tested through: microbial respiration, and 3 enzyme assays – protease, arginase and urease activity. A set of experiments to check out a pH change was also conducted. These experiments were compared with a no –treatment control using a One-way and a Two-way ANOVA test. Results concluded for sulfur showed an increase in activity regarding respiration and a decrease in activity regarding arginase and urease. Protease results were inconsistent. Results for FeEDDHA treatment showed little to no change, for all the treatments. pH levels decreased in all the sulfur treatment and in the final time for the FeEDDHA treatment.