The Effect of Urease and Nitrification Inhibitors on Soil Microbial Communities.

The application of NBPT (N-(n-butyl) thiophosphoric triamide) and Dimethylphenylpiperazinium (DMPP) has been shown to be effective in mitigating nitrogen loss from agricultural systems. However, there is still need for more information on how these chemicals affect N-cycling processes and dynamics of associated microbes in soil. A 28-day microcosm incubation experiment was established at 25^oC and 60 % water filled pore space, using 3 soil types of different characteristics and land uses, to assess the effect of NBPT and DMPP on N transformations in soil, greenhouse gas emissions from urea fertilizer application and dynamics of soil microbial communities in these soils. The treatments included Control, urea, Urea+NBPT, Urea+ DMPP and Urea + NBPT + DMPP. Data was collected by destructive sampling of soil for KCl extraction and DNA extraction on days 1,2,3,4, 7, 14, 21, and 28, with gas sampling done at time 0, 1, and 2 hours on day 1, 4, 7, 14, 18, after treatment application, to assess treatment effects on methane, nitrous oxide, and carbon dioxide emission from soil. Analysis of ammonium and nitrate concentration in soil showed that NBPT significantly reduced both nitrate and ammonium concentration in soil. Ammonium concentration was however increased by U+DMPP, and U+NBPT+DMPP compared to urea alone. The sampled gases will soon be analyzed. Molecular studies are underway from extracted DNA and will include the studies on size structure and diversity of urease gene, nitrifiers, denitrifier and methanotroph microbial communities. This study will come up with an understanding of treatment effects on gas emission and microbes. This will contribute to information on how structure and function of soil microbial communities are related and how their management could influence greenhouse gas emissions.