Wednesday, November 15, 2006

Assessing the Effects of Solarization and Sodium Azide Amendment on Selected Soil Parameters, Enzyme Activities and Microbial Diversity.

Anthony Kumi, Michelle Durant, Ramble Ankumah, Victor Khan, and Clauzell Stevens. Tuskegee University, Dept. of Agric & Environ Sciences, Tuskegee, AL 36088

The use solarization and sodium azide in controlling pathogens is being found to be an effective alternative to methyl bromide, however the long term effect on the soil is not very clear. For example sodium azide is known to be a microbial inhibitor and its effects on the indigenous microbial population have been rarely studied in the current research efforts using it as an amendment. Solarization has also been known to cause microbial shifts in the soil but its ultimate impact on ecosystem sustainability has not been studied. The objective of this research is to evaluate the effects of sodium azide and different levels of solarization on selected soil enzyme activities ( acid and alkaline phosphatses, arylsulfatase and phophodiesterase), soil chemical parameters (organic ,organic carbon and pH), soil microbial populations (“total bacteria and fungi) and microbial diversity. Soil samples were taken from a split-plot designed field from the George Washington Carver Experiment Station with two main plots (sodium azide treated and non-sodium azide treated plots) and 4 subplots (solarization for 15 days, solarization for 30 days, bare soil and agriplastic mulching). Solarization and application of sodium azide were found to significantly reduce all the soil enzymes studied. Sodium azide used in combination with solarization was found to result in the largest reduction in activity. Mulching was found to significantly reduce the effect of azide application compared to solarization. Soil pH in control bare soils was significantly increased by azide application, however in mulched soils, pH was decreased.  Overall solarization and sodium azide treatment significantly reduced both fungi and bacterial population but the responses among the various treatments varied significantly. Microbial diversity as determined by whole DNA extraction and DGGE was also found to different among the treatment.