Nitrous oxide and methane emissions from grassland treated with bark- or sawdust-containing manure at different rates

Abstract

On the main Japanese island of Honshu, bark or sawdust is often added to cattle excreta as part of the composting process. Dairy farmers sometimes need to dispose of manure that is excess to their requirements by spreading it on their grasslands. We assessed the effect of application of bark- or sawdust-containing manure at different rates on annual nitrous oxide (N2O) and methane (CH4) emissions from a grassland soil. Nitrous oxide and CH4 fluxes from an orchardgrass (Dactylis glomerata L.) grassland that received this manure at 0, 50, 100, 200, or 300 Mg ha−1 yr−1 were measured over a two-year period by using closed chambers. Two-way analysis of variance (ANOVA) was employed to examine the effect of annual manure application rates and years on annual N2O and CH4 emissions. Annual N2O emissions ranged from 0.47 to 3.03 kg N ha−1 yr−1 and increased with increasing manure application rate. Nitrous oxide emissions during the 140-day period following manure application increased with increasing manure application rate, with the total nitrogen concentration in the manure, and with cumulative precipitation during the 140-day period. However, manure application rate did not affect the N2O emission factors of the manure. The overall average N2O emission factor was 0.068%. Annual CH4 emissions ranged from −1.12 to 0.01 kg C ha−1 yr−1. The annual manure application rate did not affect annual CH4 emissions.