The effect of increasing concentration of Gallup Biograde 360 herbicide application in calcareous soil on microbial activity

Abstract

Herbicide application is a common agriculture practice to improve crop yield. When herbicides are applied, they reach the soil surface, penetrate the soil and may affect microorganisms. Microorganisms are essential to carry out basic functions within the soil such as decomposition and cycling of essential nutrients. Gallup Biograde 360, a commonly used herbicide that contains glyphosate as its active ingredient, was added to a calcareous soil in increasing concentrations (4.0 ha-1,6.0 ha-1,10.0 ha-1) and its effect on microbial activity was measured. Microbial activity was measured by monitoring 3 enzymes (arginase, protease and urease) together with the soil respiration rate. The soil was incubated for (9 weeks) weeks and the enzyme assays were run at intervals. The results showed that the herbicide amendments affected the respiration rate and arginase activity. in which the activity increases. With regards to protease and urease activities no particular pattern was observed in the results. A statistical analysis carried out for urease and protease enzymes showed no significantly decreased or increased. The relationship between the treatment concentrations or the relationship between different incubation periods were very minimal and insignificant in urease and protease enzymes. This indicates that some of the results outcome were affected by other factors however the effect in the arginase enzyme activity and the variation of the respiration rate, shows that the herbicide affected their activity.