Yield, quality and soil greenhouse gas emissions in organic and conventional fava bean crops

In this study we assessed crop yield and quality and soil greenhouse gas (GHG) emissions (N₂O and CH₄), and their interaction with soil properties, of two cultivars of fava bean (‘Muchamiel’ and ‘Palenca’) with different management practices (conventional and organic). Fava bean crops spanned from October 24, 2014 to March 13, 2015. Gas samples were taken once a week using the static gas chamber technique. Soil samples (0-30 cm) were collected from each plot at the end of the crop cycle to measure enzyme activities (β-glucosidase, β-glucosaminidase, dehydrogenase, cellulase and arylesterase). Yield and quality of the crop were determined at the end of the cycle. Results showed that the highest yield was obtained in ‘Muchamiel’ under conventional practice. A positive correlation between ‘Muchamiel’ yield and arylesterase and cellulase activities was found. In addition, ‘Muchamiel’ had the highest values in the number of seeds plant^‑1 and pod length. N₂O emissions were higher in both cultivars under organic practice, with an average increase of 29.8 mg m^‑2 in ‘Muchamiel’ and 62.7 mg m^‑2 in ‘Palenca’, with regard to those grown under conventional practice. CH₄ emissions were higher in ‘Palenca’ under both management practices. We observed significant negative correlations between N₂O emissions and β-glucosaminidase activity. CH₄ emissions showed a positive correlation with the enzyme activities arylesterase and cellulase. Pod length showed a positive correlation with N₂O emission. In summary, conventional practice increased fava bean yield and reduced N₂O emissions.