Interactive effects of liming and nitrogen management on carbon mineralization in grassland soils
2018
Lochon, Iris | Carrère, Pascal | Revaillot, Sandrine | Bloor, Juliette M.G.
Grassland management has the potential to modify soil carbon (C) mineralization, but the relative importance of combined soil improvers or fertilizers and land use intensity on C mineralization remains unclear. We used laboratory incubations to examine the interactive effects of lime addition, mineral N inputs and grassland management intensity on soil C mineralization potential over 84 days. Monitoring of CO₂ production and O₂ consumption was coupled with measurements of soil pH and microbial biomass for soils obtained from grasslands with contrasting levels of land management intensity (extensive versus intensive N management) at each of three upland sites. Lime addition increased soil pH, cumulative CO₂ production and O₂ consumption across all N treatments and soils. These positive effects of liming either partly or fully compensated the observed negative effects of N on CO₂ and O₂ fluxes. Responses to combined liming and N addition varied depending on management intensity; N addition had no effect on liming response ratios for O₂ consumption at intensively-managed sites, but increased the magnitude of positive liming response ratios for O₂ consumption at extensively-managed sites. Overall, our results suggest that the magnitude of liming-induced increases in C mineralization is mediated by effects of both past and present N management on the soil microbial community. This highlights the importance of considering agricultural practices when assessing the net contribution of agricultural liming to soil-atmosphere feedbacks on climate change.
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