Climate change and prolongation of growing season: changes in regional potential for field crop production in Finland

Abstract

Climate change offers new opportunities for Finnish field crop production, which is currently limited by the short growing season. A warmer climate will extend the thermal growing season and the physiologically effective part of it. Winters will also become milder, enabling introduction of winter-sown crops to a greater extent than is possible today. With this study we aim to characterise the likely regional differences in capacity to grow different seed producing crops. Prolongation of the Finnish growing season was estimated using a 0.5º latitude × 0.5º longitude gridded dataset from the Finnish Meteorological Institute. The dataset comprised an average estimate from 19 global climate models of the response of Finnish climate to low (B1) and high (A2) scenarios of greenhouse gas and aerosol emissions for 30-year periods centred on 2025, 2055 and 2085 (Intergovernmental Panel on Climate Change). Growing season temperature sums that suit crop growth and are agronomically feasible in Finland are anticipated to increase by some 140 °Cd by 2025, 300 °Cd by 2055 and 470 °Cd by 2085 in scenario A2, when averaged over regions, and earlier sowing is expected to take place, but not later harvests. Accordingly, the extent of cultivable areas for the commonly grown major and minor crops will increase considerably. Due to the higher base temperature requirement for maize (Zea mays L.) growth than for temperate crops, we estimate that silage maize could become a Finnish field crop for the most favourable growing regions only at the end of this century. Winters are getting milder, but it will take almost the whole century until winters such as those that are typical for southern Sweden and Denmark are experienced on a wide scale in Finland. It is possible that introduction of winter-sown crops (cereals and rapeseed) will represent major risks due to fluctuating winter conditions, and this could delay their adaptation for many decades. Such risks need to be studied in more detail to estimate timing of introduction. Prolonged physiologically effective growing seasons would increase yielding capacities of major field crops. Of the current minor crops, oilseed rape (Brassica napus L.), winter wheat (Triticum aestivum L.), triticale (X Triticosecale Wittmack), pea (Pisum sativum L.) and faba bean (Vicia faba L.) are particularly strong candidates to become major crops. Moreover, they have good potential for industrial processing and are currently being bred. Realisation of increased yield potential requires adaptation to 1) elevated daily mean temperatures that interfere with development rate of seed crops under long days, 2) relative reductions in water availability at critical phases of yield determination, 3) greater pest and disease pressure, 4) other uncertainties caused by weather extremes and 5) generally greater need for inputs such as nitrogen fertilisers for non-nitrogen fixing crops. Key-words:Climate change, cultivation area, yield, potential, barley, oat, wheat, rye, triticale, rapeseed, pea, maize, seed crops, minor...

Projected changes in thermal seasons and the growing season in Finland

“…For summer, by contrast, several models simulate reduced cloudiness and increasing radiation, albeit projections are more divergent than those for winter. Peltonen-Sainio et al (2009b) studied the 'physiologically effective' growing season for spring cereals, applying the same climate data as in the present work. In order to take into account the unfavourable insolation and harvesting conditions in autumn, they terminated the effective growing season on 15 September.…”

“…Increases in the length and warmth of the growing season improve the agriculture potential in high latitudes (Peltonen-Sainio et al, 2009b). For example, the cultivable limits of spring wheat are projected to shift substantially northward (Saarikko and Carter, 1996), and even the cultivation of maize may become profitable in Finland (Fronzek and Carter, 2007).…”

Growing season precipitation in Finland under recent and projected climate

“…Coastal regions in south-western Finland typically suffer from early summer drought during the major period of yield determination in spring sown seed crops (Peltonen-Sainio et al, 2009b). Observations suggest that the early summer drought has eased off slightly in the SW area, particularly so during 1961-2000.…”

“…In the future, prominent increases in precipitation are needed in early summer for growth and yield determination of the crops that are estimated to have markedly improved yield potentials and biomass production capacities (Peltonen-Sainio et al, 2009b). Higher biomasses, together with elevated temperatures, will cause higher pressure for evapotranspiration.…”

Recent warming across the North Atlantic region may be contributing to an expansion in barley cultivation

“…Equation 1 uses a base temperature of 5°C which is commonly used for barley in northern areas (Peltonen-Sainio et al 2009; Supplementary Note 1). When a month's average temperature was less than 5°C, it was considered to have zero degree days.…”