Strategies for carbon sequestration in agricultural soils in northern Europe

Abstract

We present new and synthesize published results from long-term field studies exploring management options for carbon sequestration in cropland and grassland. Agricultural practices were evaluated within the framework set by global food demand and limited area available for agricultural production. Among options for higher C sequestration, we found minimizing the time with bare soil, improving recycling of organic materials and increasing yields through N fertilization to be efficient. Indeed, our results suggest that C stocks can increase with 1–2 kg C for each kg of mineral N fertilizer applied. Possibilities to decrease C emissions by reduced tillage were found to be limited under Nordic conditions. Options for reducing C emissions from drained cultivated organic soils are limited when used as cropland. Extensive production leads to lower soil C stocks and requires more land. Increasing photosynthesis at the global scale by intensification of crop production was found to be the most effective mitigation option and is a prerequisite for preventing further areal expansion of agriculture.

Keywords:

• Greenhouse gases
• land use change
• long-term field experiments
• mitigation
• organic farming
• soil organic carbon
• subsoil

Acknowledgements

Thanks to the organizers of the symposium on “Agriculture and greenhouse gases”, held November 2012 in Oslo, for inviting us to prepare this keynote paper. Parts of the work on the Swedish long-term trials were funded by the Swedish Farmer's Foundation for Agricultural Research. We gratefully acknowledge former and present colleagues for starting and maintaining these field experiments. We also acknowledge Dr. Aroha Miller for language checking and two anonymous reviewers for valuable comments.