Soil nitrous oxide emissions after the introduction of integrated cropping systems in subtropical condition

Abstract

The assessment of impacts of GHG to mitigate emissions in Brazil is a significant challenge for the expansion of integrated cropping systems. In Brazil, most studies on integrated cropping systems were conducted in tropical regions and evaluated N2O fluxes, important GHG due to its global warming potential. However, the dynamics of N2O fluxes of these systems in subtropical climate conditions in Brazil are still unclear. Thus, we investigated N2O emissions under integrated cropping systems and monoculture systems and evaluated N2O fluxes in five consolidated systems: cropland, integrated crop-forest (ICF), pasture, integrated livestock-forest (ILF), and eucalyptus. N2O emissions were monitored weekly using six manual static chambers for each agricultural system. Soil-weather variables were observed consecutively during N2O sampling. We assessed the relation between soil moisture, water-filled porous space (WFPS), rainfall, soil NO3-, and soil NH4+ with N2O. Our results showed that seasonal water availability influenced N2O fluxes in all five systems. Fertilization with N increased N2O daily fluxes in cropland and ICF (N2O maximum from 30 to 50 μg N m−2 h−1). However, cumulative N2O in the second season was lower than the first season to all evaluated systems. Cropland, ICF, and eucalyptus showed an increase of more than 50% of cumulative N2O emissions compared to the dry to the rainy season, while pasture and ILF presented an increase of more than 200% of cumulative N2O from one season to another. However, the absolute cumulative value was higher for cropland, ICF, and eucalyptus than pasture systems. Thus, the use of annual crops or just monoculture could increase N2O fluxes due to the influence of weather-soil variables. The results showed that N2O emissions were similar between ICF and ILF systems and between cropland, pasture, and eucalyptus. Therefore, integrated cropping systems offer potential for reduced N2O losses to the atmosphere and may support national and international climate change initiatives to reduce GHG emissions in agriculture.