Climate change adaptation in arable land use, and impact on nitrogen load at catchment scale in northern agriculture

Prolongation of the growing season due to a warming climate could represent new opportunities for northern agriculture. Climatic and biotic constraints may, however, together with increasing risk for higher nutrient loads, challenge future crop production. The objective of this study was to speculate how a range of arable land use patterns, resulting from various policy driven choices, could be introduced into a farming system, and how they would affect the risks associated with nutrient leaching. The case study area included 720 ha of arable fields in southern Finland. Climate change scenarios were calculated using averages of 19 climate models and emission scenarios B1, A1B and A2. Four crop choice and allocation storylines were developed according to policy objectives: increased protein self-sufficiency, increased winter cover for reducing nutrient loading, diversification, and monoculture for cereal production. Grasslands and leys were not included in any of the production scenarios. Impacts of these land uses on sediment loading and nitrogen leaching were simulated using WSFS and INCA modelling. We found that while adaptation to climate change must include consideration of crop choices, there are conflicts associated with allocations and rotations for various market and policy situations. The expected increase in nutrient loading in the simulations caused by climate change was moderate. The increase can partly be compensated for by changes in farmland use, more in the shorter term than in the longer term to mid-century. To reduce suspended sediment load in the changed climate, vegetation cover in winter was important. For nitrogen leaching, adjusting the N balance at parcel level was more important than vegetation cover. In the future, adaptation at cropping system level is potentially an efficient way to manage nutrient load risks.