Management Practices of Miscanthus × giganteus Strongly Influence Soil Properties and N2O Emissions Over the Long Term
2017
Peyrard, Céline | Ferchaud, Fabien | Mary, Bruno | Gréhan, Eric | Léonard, Joël
Cropping practices of Miscanthus × giganteus, a promising energy crop, can influence C and N cycles and therefore potentially affect N₂O emissions. They may vary in harvesting date, either early (EH) or late harvest (LH), and the fertiliser form (NH₄ or NO₃). In this study, we combined a long-term field experiment and simulations with the STICS model to investigate the effect of these practices on soil parameters, N₂O emissions and the contribution of nitrification and denitrification. Daily N₂O fluxes and soil parameters were measured during the 4-month period following fertilisation in 2014 and 2015. Mean cumulative N₂O emissions were markedly higher in LH than EH (4.21 vs. 0.89 kg N₂O–N ha⁻¹ year⁻¹) but did not differ significantly between fertiliser forms or years. The difference was mainly attributed to the higher soil water-filled pore space (WFPS) observed in LH (80 vs. 56 % in EH) which resulted itself from the leaf mulch present in LH and not in EH. WFPS explained 67 % of the variance of N₂O emissions. The large decrease in pH observed after NH₄ fertilisation stimulated N₂O emissions probably through less-efficient reduction of N₂O to N₂ as simulated by STICS. Model outputs suggest a large contribution of nitrification in EH and a dominant contribution of denitrification in LH. Our study highlights the crucial impact of management practises on N₂O emissions in Miscanthus crops through changes in physico-chemical parameters and soil processes on the short and long term and brings knowledge required to maximise the benefits of bioenergy crops.
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