Solid Oxygen Fertilizer and Biochar Applications Reducing Nitrous Oxide Production from Agricultural Soil.

Production of N2O from well-fertilized agricultural soils is a major pathway to lose nitrogen (N) under oxygen limited condition which is caused by events, such as heavy rainfall or over-irrigation practices. In this study, solid oxygen fertilizers and biochars were used to mitigate the N2O production, hence reduce the N loss from the moist soil. Treatments included: (i) Soil without N fertilizer (S); (ii) S + 224 kg N ha-1 as ammonium nitrate (S + N); (iii) S + Corn Stover biochar (CB) @ 10 Mg ha-1 (S+CB); (iv) S + N + CB; (v) S + Pine Bark biochar (PB) @ 10 Mg ha-1 (S + PB); (vi) S + N + PB (vii) S + N + Calcium peroxide @ 10 Mg ha-1 (S+N+CPO); (vii) S + N + PB (viii) S + N + Magnesium peroxide @ 10 Mg ha-1 (S + N + MPO). Two soils viz. sandy soil with low organic carbon (MS) and sandy clay loam soil with high organic carbon (OS) were collected from Plant Science Research and Education Unit, near Citra, FL, and Everglades Research & Education Center, Belle Glade, FL, respectively. The study was conducted in the completely randomized design with three replications by incubating the soils with the treatments for 22 (MS) and 24 (OS) days. Cumulative N2O production was greater from OS than MS for each of the treatments in this experiment. Among the N treatments, S + N + CPO produced least cumulative N2O (51 µg g^-1 MS and 17802 µg g^-1 OS), while S + N produced greatest cumulative N2O (7705 µg g^-1 MS and 23757 g g^-1 OS) for both soils. There were 98% and 99% reduction of cumulative N2O production from MS treated with either MPO or CPO, respectively along with N compared to MS treated with only N. Addition of CB to MS with N increased 201% N2O production compared to MS + N. The S + N + CO, S + N + CB, S + N + PB and S + N + MO reduced cumulative N2O production by 25%, 23%, 13% and 7%, respectively for OS. The activity of each of three tested soil enzymes, namely, Leucine aminopeptidase, N-acetyl-β-D glucosaminidase and β-Glucosidase was significantly altered by solid oxygen fertilization for MS, but not for OS. For both MS and OS, soil microbial biomass was reduced by the oxygen fertilization. Thus, application of both oxygen fertilizers reduced the cumulative N2O production from low and high organic soil in laboratory incubation and can be used for field testing in future. These findings may provide a new method to minimize N2O production on agricultural soils.