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Title: The influence of microbial-based inoculants on N2O emissions from soil planted to corn under greenhouse conditions with different nitrogen fertilizer regimens

Author
item CALVO, PAMELA - Auburn University
item Watts, Dexter
item KLOEPPER, JOSEPH - Auburn University
item Torbert, Henry - Allen

Submitted to: Canadian Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/25/2016
Publication Date: 8/19/2016
Citation: Calvo, P., Watts, D.B., Kloepper, J.W., Torbert III, H.A. 2016. The influence of microbial-based inoculants on N2O emissions from soil planted to corn under greenhouse conditions with different nitrogen fertilizer regimens. Canadian Journal of Microbiology. 62:1041-1056.

Interpretive Summary: Nitrous oxide (N2O) emissions are increasing at an unprecedented rate due to increased nitrogen (N) fertilizers use. Thus, new innovative management tools are needed to reduce emissions. One potential approach is the use of microbial inoculants in agricultural production which have been shown to reduce N2O emissions when added to soil with N fertilizers under laboratory incubations. This study evaluated the effects of microbial-based inoculants on N2O and carbon dioxide (CO2) emissions when applied to soil planted with corn. Inoculant treatments consisted of: (1) SoilBuilder; (2) a metabolite extract of SoilBuilder; and (3) a mixture of four strains of plant growth-promoting Bacillus spp. Experiments included an unfertilized control and three nitrogen fertilizers: urea, urea ammonium nitrate, and calcium ammonium nitrate. Overall, results demonstrate that microbial inoculants can reduce N2O emissions following fertilizer application depending on the N fertilizer type used and enhance N uptake and plant growth.

Technical Abstract: Nitrous oxide (N2O) emissions are increasing at an unprecedented rate due to increased nitrogen (N) fertilizers use. Thus, new innovative management tools are needed to reduce emissions. One potential approach is the use of microbial inoculants in agricultural production. In a previous incubation study, we observed reductions in N2O emissions when microbial-based inoculants were added to soil (no plants present) with N fertilizers under laboratory incubations. This study evaluated the effects of microbial-based inoculants on N2O and carbon dioxide (CO2) emissions when applied to soil planted with corn (Zea mays L.) under controlled greenhouse conditions. Inoculant treatments consisted of: (1) SoilBuilder (SB); (2) a metabolite extract of SoilBuilder (SBF); and (3) a mixture of four strains of plant growth-promoting Bacillus spp. (BM). Experiments included an unfertilized control and three nitrogen fertilizers: urea, urea ammonium nitrate 32% N (UAN-32), and calcium ammonium nitrate 17% N (CAN-17). Cumulative N2O fluxes from pots 41 days after planting (DAP) showed significant reductions of 15% (SB), 41% (BM), and 28% (SBF) with CAN-17 fertilizer. When UAN-32 was used, reductions of 34% (SB), 35% (SBF), and 49% (BM) were obtained. However, no reductions in N2O emissions occurred with urea. Microbial-based inoculants did not affect total CO2 emissions from any of the fertilized treatments or unfertilized control. Nitrogen uptake was increased by an average of 56% with microbial inoculants compared to the control (no microbial based treatments). Significant increases in plant height, SPAD chlorophyll readings, and fresh and dry shoot weight were also observed when the microbial-based treatments were applied (with and without N). Overall, results demonstrate that microbial inoculants can reduce N2O emissions following fertilizer application depending on the N fertilizer type used and enhance N uptake and plant growth. Future studies are planned to evaluate the effectiveness of these microbial inoculants in field based trials and determine the mechanisms involved in N2O reduction.