Understanding the flux of nitrous oxide from the eucalypt soil in monoculture and Integrated Crop–Livestock–Forest systems

The Brazilian agricultural sector is largely responsible for nitrous oxide (N2O) soil emissions, mainly due to beef cattle and the use of synthetic nitrogen fertilizers. Therefore, Brazil is looking for measures, such as integrated crop–livestock– forest (ICLF), to increase productivity and reduce greenhouse gas emissions in this sector. The forest component within this system plays a positive role in the context of climate change, soil conservation, carbon dioxide (CO2) sequestration, and biodiversity protection. The aim of this study was to evaluate the effect of management and rainfall on N2O emissions in eucalypt monoculture soils and eucalypt soils in ICLF systems. Manual static chambers were used to collect gas samples, from November 2013 to October 2014, in four treatments, i.e., one eucalypt monoculture (F) and three modalities of ICLF (livestock–forest [LF], livestock–crop–forest [LCF], and integrated crop–livestock–forest [ICLF]). A gas chromatograph with an electron capture detector was used to measure the N2O concentrations. The results showed that rainfall considerably affected N2O fluxes across all the treatments, indicating that rainfall is the main factor in increasing emissions. During the wet season, the N2O levels ranged from 0.158 to 0.482 kg N-N2O ha-1 across all treatments. During the dry season, all treatments behaved like sinks of N2O. Moreover, N2O flux did not differ between the soils in the eucalypt monoculture and ICLF systems. This indicates that the forestry component in the ICLF systems did not affect N2O soil fluxes.