Warming autumns at high latitudes of Europe: an opportunity to lose or gain in cereal production?

Climate change is projected to prolong Finland's short growing season at both ends though warming autumns are not expected to benefit arable crops such as cereals, in contrast to warming springs. To test the veracity of this, ex-post and ex-ante approaches were applied to assess the past and future roles of autumns on cereal growth. Long-term multi-location data were used to assess the response of spring cereal cultivars on late harvests in the past. Future changes in temperature and precipitation, derived from the simulations performed with 28 global climate models under the RCP4.5 and RCP8.5 scenarios, compared with a baseline period, with mid-point year 1986, were averaged for three 30-year periods with mid-point years of 2025, 2055, and 2085. The phenological timing of growing seasons in a changing climate was simulated with the WOFOST. Warming autumns have insignificant potential for additional cereal yield gains. Even the latest maturing wheat cultivars would mature by the same time or earlier than currently when sown earlier. However, inter-annual variability in harvest times remains high, and hence many emerging risks may result from the elevated autumn precipitation in the future that will accompany delayed harvests. Means to benefit from warming autumns and mitigate their potential harmful impacts, like increasing nutrient leaching, erosion, and soil compaction, are needed. Post-harvest sowing of nutrient scavenging catch crops may provide the necessary soil cover, produce biomass, increase soil carbon, and protect soil from erosion and compaction. Hence, double cropping may be a viable alternative to safeguard sustainable high-latitude agriculture in a changing climate.