Emissions of Nitrous Oxide and Methane in a Subtropical Ferralsol Subjected to Nitrogen Fertilization and Sheep Grazing in Integrated Crop-Livestock System

Abstract

Brazilian agriculture contributes significantly to nitrous oxide (N 2 O) and methane (CH 4 ) emissions, so the understanding of such emissions at the field is crucial for mitigation strategies. This study quantified the impact of N application and sheep grazing on the N 2 O and CH 4 emissions from a subtropical Ferralsol under an integrated crop-livestock (ICL) management system. In a long-term experiment in southern Brazil, gaseous fluxes were measured during a year-long cycle of ryegrass (Lolium multiflorum) plus oats (Avena sativa) winter pasture and a summer crop of common beans (Phaseolus vulgaris). Three rates of urea-nitrogen (0, 75, and 150 kg ha -1 ) were applied to the winter-pasture, which was subjected to two sheep grazing levels (continuously grazed, and ungrazed). The experiment had a complete randomized block design with three replicates. Soil N 2 O and CH 4 fluxes were measured with closed static-chambers (0.20 m high × 0.25 m in diameter). Nitrous oxide emission peaks occurred 28 days after N application and increased with N application rate. Accordingly, the cumulative N 2 O emissions averaged across grazed and ungrazed treatments increased from 0.45 kg ha -1 in the control soil to 1.78 and 2.10 kg ha -1 after application of 75 and 150 kg ha -1 , respectively. The N 2 O emission factors were 1.7 and 1.1 % when the N rates were 75 and 150 kg ha -1 , respectively. The cumulative average N 2 O emission for all N rates was 2.09 kg ha -1 in ungrazed pasture, but it was reduced by 62 % with grazing to 0.80 kg ha -1 , perhaps because of a possible denitrification of N 2 O to N 2 associated with soil compaction from trampling. Overall, fertilizer-N is an important source of N 2 O from soil under ICL based on sheep grazing, with emission factors consistent with the IPCC's default of 1 % (0.3-3.0 %). Grazing reduced the emission of soil N 2 O, but the underlying cause of that reduction needs to be better understood.

Contribution of pecan (Carya illinoinensis [Wangenh.| K. Koch) to Sustainable Development Goal 2 under the dual perspective of carbon storage and human nutrition

“…Thus, the assessment of the environmental impacts caused by agricultural systems has increasing focus, as well as the development of technologies and agricultural management practices to reduce and offset these impacts (29, 30). Agricultural management practices can significantly change the dynamics of GHG emission; thus, it is essential to study and monitor GHG fluxes in different climate and soil conditions (31)(32)(33).…”

Technologies to Reduce Emission of Methane and Nitrous Oxide in Rice Fields: A Brief Review

“…The agricultural sector is a source of GHG production, especially methane (CH 4 ) and nitrous oxide (N 2 O), which comes from rice fields, biomass burning, agricultural land, enteric fermentation, livestock manure management (Mosier et al, 2004;Jugold et al, 2012;Zhang et al, 2020). In the last two decades, concentrations of CH 4 and N 2 O in the atmosphere have increased at a rate of 0.9% and 0.3% per year, respectively (Wihardjaka et al, 2011;Piva et al, 2019). CH 4 and N 2 O contribute to 25 times and 298 times the greenhouse effect by CO 2 , respectively, and 50% and 60% of greenhouse gases are generated by agricultural activity (Kang et al, 2021).…”