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29 January 2021 Nitrogen turnover and N2O production in incubated soils after receiving field applications of liquid manure and nitrification inhibitors
Sisi Lin, Guillermo Hernandez-Ramirez
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Applying abundant manure to soils can accelerate nitrogen (N) transformations and nitrous oxide (N2O) emissions. We conducted a laboratory incubation to examine the turnover of labile N in manured soils. Soils were collected from agricultural fields that had recently received spring-injected liquid dairy manure with or without admixing nitrification inhibitors. Bands and interbands of the manure plots were incubated separately. Time courses of ammonium (NH4+) and nitrate (NO3) were used to derive and contrast zero-, first-, and second-order kinetics models. We found that nitrification rates were consistently better represented by first-order kinetics (k1). Furthermore, across all evaluated soils, the dependency of nitrification rate (k1 of NH4+) on initial NH4+ concentration was modelled by Michaelis–Menten kinetics reasonably well, with an affinity (Km) of 63 mg N·kg−1 soil (R2 = 0.82). Compared with the manure interbands, the initially NH4-enriched bands had a much faster nitrification rate, with half-life for NH4+ of only 4 d and rapid k1 (0.186 versus 0.011 d−1). Soil N substrate and k1 exerted control on N2O production. Nitrous oxide production increased linearly with both measured NH4+ intensity (R2 = 0.47) and modelled k1–NH4+ (R2 = 0.48). Conversely, N2O production increased non-linearly with NO3 intensity (R2 = 0.68), where high NO3 caused a saturation plateau with a threshold of 96 mg N·kg−1·d−1 — beyond which no additional N2O was produced. During peak N transformations, measured N2O-N flux was 1.4% ± 0.3% of the inorganic N undergoing nitrification. Heavily manured soils exhibited augmented N turnover that increased N2O fluxes, but inhibitors reduced these emissions by half.

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Sisi Lin and Guillermo Hernandez-Ramirez "Nitrogen turnover and N2O production in incubated soils after receiving field applications of liquid manure and nitrification inhibitors," Canadian Journal of Soil Science 101(2), 290-304, (29 January 2021).
Received: 13 August 2020; Accepted: 18 January 2021; Published: 29 January 2021

liquid manure
nitrification inhibitor
nitrogen processes
nitrous oxide
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