Soil Greenhouse Gas Emissions in Different Pastures Implemented as a Management Strategy for Climate Change

The increase in global average temperature has significant implications for food security and agriculture production. Grass species adapted to new climate scenarios are essential for the success of livestock production. The aim of this study was to evaluate different forage species, providing animal feed during critical dry periods as an adaptation strategy for livestock grazing systems, and its implications for greenhouse gas (GHG) emissions. The field experiment was conducted during September 2015 to September 2017, with four treatments (n = 5, completely randomized block design), including two perennial forages, Bromus valdivianus (Bromus), Lotus corniculatus (Lotus), alone and in a mixture pasture (Br/L). As a control treatment, the forage species commonly seeded by the farmer was used (hybrid ryegrasses + Oat, Control). One-half of the plots was used for nitrous oxide (N2O) and methane (CH4) measurements, and the remaining half for destructive soil and forage sampling. Gas fluxes were measured using the static chambers technique. Cumulative emissions of N-N2O, C-CH4 and CO2-eq were not affected by treatments, averaging 1.7 kg N-N2O ha(-1), 3.2 kg C-CH4 ha(-1) and 635.5 kg CO2 ha(-1), respectively (p > 0.05). However, emission intensity tended to be lower for Br/L compared with other treatments (p = 0.06) during the second year, while pasture yield was greater for Br/L (p < 0.05). The control showed a greater average pasture yield (first and second years) compared to other treatments, with the highest metabolizable energy and the lowest crude protein content. Our results suggest that a mix pasture Br/L as a management strategy would promote farm adaptation, given that it favors pasture yield at critical dry periods during the year. This inclusion also reduces N-N2O emissions from grassland soils as well as favoring C-CH4 capture. Our study determined that N-N2O and C-CH4 emissions were regulated by soil variables, mainly soil moisture and soil temperature. Extension and knowledge transfer should be provided to farmers to account for potential adoption barriers, such as low short-term yield.