Cattle Slurry Applied Before Fertilizer Nitrate Lowers Nitrous Oxide and Dinitrogen Emissions
2002
Stevens, R James | Laughlin, Ronald J.
Nitrous oxide emissions increase because of denitrification in the first few days after cattle (Bos taurus) slurry (CS) is applied to grassland soils fertilized with NO₃ Denitrifying conditions are created when the readily decomposable C in the CS is oxidized by the soil microbial biomass when NO₃ is present and O₂ is deficient. Half of the readily decomposable C in CS can be volatile fatty acids (VFAs) that take up to 4 d to degrade. The timing of CS application relative to fertilizer-NO₃ application could therefore affect the losses of N₂O and N₂ We used the ¹⁵N gas-flux method to measure N₂O and N₂ fluxes from grassland when CS containing 60 kg NH₄-N ha⁻¹ was applied 4, 3, 2, 1, and 0 d before the application of 60 kg N ha⁻¹ of K¹⁵NO₃ For a field experiment repeated in April, May, August, and October 1998, CS applied 3 or 4 d before KNO₃ had no significant effect in any month on the flux of N₂O in the 124 h after KNO₃ application. On average over all months, the extra emission of N₂O-N over the control was equivalent to 0.8, 1.1, and 2.9% of KNO₃-N for prior applications of CS at 2, 1, and 0 d, respectively. When CS was applied 4 d prior to KNO₃ there was no significant effect on the flux of N₂ in any month. The maximum loss of N₂O + N₂ was 8.3% of the KNO₃ applied (5 kg N ha⁻¹) when CS and KNO₃ were applied at the same time in April.
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