Soil N₂O emissions following cover‐crop residues application under two soil moisture conditions

Abstract

Cover crops in rotation or intercropped with annual crops are important strategies to increase C and N input in agricultural soils. However, these practices may also enhance soil N 2 O emissions. The effect on N 2 O emissions may be dependent upon the biochemical composition of cover crop residues. A 47-d incubation study was conducted to determine soil N 2 O emissions following the addition of residues from three summer legume species [pigeon pea (Cajanus cajan L. Millsp.), cowpea (Vigna unguiculata L. Walp.), lablab bean (Lablab purpureus)], one winter legume [vetch (Vicia sativa L.)], one winter monocotyledon [black oat (Avena strigosa Schreb.)], and maize (Zea mays L.) under two water-filled pore space levels (40 and 70% WFPS). Short-term peaks of N 2 O fluxes were observed after the addition of all crop residues, but were much greater under 70 than 40% WFPS (5.2 and 5133 μg N-N 2 O kg -1 soil for 40 and 70% WFPS, respectively). Under both WFPS, significantly higher peaks were detected after the application of N-rich legume residues (7.7 and 3,356 μg N-N 2 O kg -1 soil under 40 and 70% WFPS, respectively) than after the application of grass residues (2.8 and 1,777 μg N-N 2 O kg -1 soil under 40 and 70% WFPS, respectively). Cumulative soil N 2 O produced under 70% WFPS was approx. 110 times greater than under 40% WFPS. Soil N 2 O emissions increased linearly as residue N content increased. Soil N 2 O emissions also increased linearly as the content of the recalcitrant compounds lignin and polyphenols increased, because residues with high N content also had high lignin and polyphenols content. When the content of C and recalcitrant compounds were expressed on an N basis, soil N 2 O emission decreased linearly as residue C/N, lignin/N, polyphenol/N, and (lignin + polyphenols)/N ratios increased. Indices that include recalcitrant compounds on N basis may be useful for the selection of cover-crop species with the least impact on soil N 2 O emissions. However, our results show that these ratio indices had similar correlation coefficients compared to C/N ratio, indicating that C/N ratio is an efficient index to predict soil N 2 O emission following cover crop application.

Crop residue harvest for bioenergy production and its implications on soil functioning and plant growth: A review

“…Diverse factors affect directly or indirectly the production and emission of GHG, contributing to the variability of the results found in the literature. These factors could be environmental, edaphic and related to the quality and quantity of the material used to cover the soil (Pimentel et al, 2015).…”

The influence of tillage on N<sub>2</sub>O fluxes from an intensively managed grazed grassland in Scotland

“…The mechanisms driving these large sustained fluxes are believed to be partly due to the mineralisation of organic materials in the soils (decaying grass materials from the previous sward in tilled grasslands) (Baggs et al, 2003;Hellebrand, 1998;Pimentel et al, 2015). The large quantities of decaying organic matter ploughed into the soils would have provided a gradual release of carbon and nitrogen into the soils, which provide substrate for the microbial processes of nitrification and denitrification (Pimentel et al, 2015;Seastedt et al, 1992). According to IPCC estimates, 1 % of N added to soils in the form of crop residues can be expected to be released as N 2 O (IPCC, 2006).…”

Diurnal pattern of nitrous oxide emissions from soils under different vertical moisture distribution conditions

“…High temperature and the soil water evaporation rate might have contributed to high N2O emissions on 22 April and 6 May. The WFPS at the 0-12 cm soil depth on 17 June, 1 July, and 22 July was 46% to 59%, 26% to 60%, and 20% to 47%, respectively, but N2O fluxes decreased gradually on these dates perhaps because N2O emissions increased with increased soil moisture within a certain range of soil WFPS (Peng et al, 2009;Pimentel et al, 2015) (Figures 1d, 1e, and 1f). The maximum N2O flux (3677.4 μg N2O m -2 h -1 ) was observed on 17 June when WFPS (46% to 59%) at the 0-12 cm soil depth was within the reported optimal soil WFPS range (45% to 75%) for peak N2O emissions (Bateman and Baggs, 2005;Khalil and Baggs, 2005;Sey et al, 2008;Castellano et al, 2010;Laville et al, 2011).…”