The effects of zinc on soil microbial activity

Abstract

Microbial activity in soil is an important factor. It keeps a soil healthy as it plays an important aspect in nutrient cycling. Microbial activity is sensitive to a number of factors such as pollutants. Heavy metals such as Zn could be a common soil contaminant. Zn based fungicides are used extensively in Malta and these together with the practice of farm yard manure application to soil could lead to high levels of Zn. The effect of Zn on soil microbial activity was investigated. A Luvisol from Malta was amended with increasing concentrations (100, 150 and 300 ppm) of Zn and incubated under controlled conditions for 8 weeks. Microbial activity was tested at two weeks’ interval by performing an arginase, urease and protease enzyme assays and a respiration rate test. The findings of this study did not show a clear effect of Zn on soil microbial activity. This could be due to a number of factors which could include, a low level of contamination, availability of cation caused by the high soil pH, and also fluctuations in soil water content. Soil microbial activity was low due to the fact that soils of Malta are very low in organic matter content. Furthermore, soil pH influences Zn and its availability, the highest concentration of Zn used (300 ppm) was reduced to 205 ppm Zn as the available form.