Soil bacterial communities to agricultural wastes and consequences for N2O emissions. Agr

There is an emerging need to reduce N chemical fertilizers and using agricultural organic wastes as organic amendments could be a valuable strategy to reduce GHG emissions and sustain agro-ecosystems productivity. An incubation experiment was performed to examine the effects of agricultural wastes application on soil bacterial community as well as CO2 and N2O direct emissions. Untreated soils compared with soils received the same amount of N (100 μg/g soil) in the form of mineral fertilizer and organic agricultural waste. In particular, soils were incubated with three different organic agricultural wastes, orange (OP), mandarin (MP) and banana peels (BP) and ammonium nitrate (NH4NO3) after adjusting soil water at 70% of its holding capacity. We described the microbial community structure using next generation sequencing of amplified 16sRNA and found that both treatment and time had a strong effect on the microbial assemblages. Agricultural wastes stimulated the growth of copiotrophic bacterial groups like Proteobacteria and Firmicutes while the abundance of most bacterial Phyla detected was suppressed. We found that direct soil N2O emission is positively associated to bacterial diversity in soil while the highest cumulative emission was calculated in fertilized treated soils. Interestingly, soils received organic amendments exhibited a substantial reduction of the abundance of bacterial species that have been associated with N2O emissions. Apparently, the lower N2O emission found in soils incubated with agricultural organic waste is related to lower substrate availability and possibly due to the proliferation of N2O reducers. Our study represents a basis for future research regarding the impact of different organic amendments on soil denitrifying community and bacterial community networks and how pivotal key genes are influenced upon their application in soils.