Kaija Hakala

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

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.

Sensitivity of barley varieties to weather in Finland

SUMMARY Global climate change is predicted to shift seasonal temperature and precipitation patterns. An increasing frequency of extreme weather events such as heat waves and prolonged droughts is predicted, but there are high levels of uncertainty about the nature of local changes. Crop adaptation will be important in reducing potential damage to agriculture. Crop diversity may enhance resilience to climate variability and changes that are difficult to predict. Therefore, there has to be sufficient diversity within the set of available cultivars in response to weather parameters critical for yield formation. To determine the scale of such ‘weather response diversity’ within barley (Hordeum vulgare L.), an important crop in northern conditions, the yield responses of a wide range of modern and historical varieties were analysed according to a well-defined set of critical agro-meteorological variables. The Finnish long-term dataset of MTT Official Variety Trials was used together with historical weather records of the Finnish Meteorological Institute. The foci of the analysis were firstly to describe the general response of barley to different weather conditions and secondly to reveal the diversity among varieties in the sensitivity to each weather variable. It was established that barley yields were frequently reduced by drought or excessive rain early in the season, by high temperatures at around heading, and by accelerated temperature sum accumulation rates during periods 2 weeks before heading and between heading and yellow ripeness. Low temperatures early in the season increased yields, but frost during the first 4 weeks after sowing had no effect. After canopy establishment, higher precipitation on average resulted in higher yields. In a cultivar-specific analysis, it was found that there were differences in responses to all but three of the studied climatic variables: waterlogging and drought early in the season and temperature sum accumulation rate before heading. The results suggest that low temperatures early in the season, delayed sowing, rain 3–7 weeks after sowing, a temperature change 3–4 weeks after sowing, a high temperature sum accumulation rate from heading to yellow ripeness and high temperatures (⩾25°C) at around heading could mostly be addressed by exploiting the traits found in the range of varieties included in the present study. However, new technology and novel genetic material are needed to enable crops to withstand periods of excessive rain or drought early in the season and to enhance performance under increased temperature sum accumulation rates prior to heading.

Pests and diseases in a changing climate: a major challenge for finnish crop production

A longer growing season and higher accumulated effective temperature sum (ETS) will improve crop production potential in Finland. The production potential of new or at present underutilised crops (e.g. maize (Zea mays L.), oilseed rape (Brassica napus L.), lucerne (Medicago sativa L.)) will improve and it will be possible to grow more productive varieties of the currently grown crops (spring wheat (Triticum aestivum L.), barley (Hordeum vulgare L.), oats (Avena sativa L.)). Also cultivation of autumn sown crops could increase if winters become milder and shorter, promoting overwintering success. Climatic conditions may on the other hand become restrictive in many ways. For example, early season droughts could intensify because of higher temperatures and consequent higher evaporation rates. Current low winter temperatures and short growing season help restrict the development and spread of pests and pathogens, but this could change in the future. Longer growing seasons, warmer autumns and milder winters may initiate new problems with higher occurrences of weeds, pests and pathogens, including new types of viruses and virus vectors. Anoxia of overwintering crops caused by ice encasement, and physical damage caused by freezing and melting of water over the fields may also increase. In this study we identify the most likely changes in crop species and varieties in Finland and the pest and pathogen species that are most likely to create production problems as a result of climate change during this century.

Chapter 4 – Improving Farming Systems in Northern European Conditions

Publisher Summary The breeding cultivars adapted to northern growing conditions and developing crop management to sustain yield potential have represented exceptional challenges for Northern Europe, compared with the global, large-scale challenges that crop production typically faces. During earlier decades, development was largely based on testing management practices and application of methods for large-scale comparative trials, in which yield response per se, economic outcome, and general applicability of the method were often sufficient for adopting a novel method or systems; crop physiology did not contribute much to these early developments. However, crop physiology will evidently play a far more important role in the future in plant breeding and developing crop management practices as climate and cropping systems change in line with the extended growing season.

Comparing regional risks in producing turnip rape and oilseed rape – Impacts of climate change and breeding

Abstract Summer turnip rape (Brassica rapa L.) is the dominant oilseed crop in Finland. It has lower production risks compared with summer oilseed rape (Brassica napus L.). However, climate-change-induced increases in temperature accumulation could favour oilseed rape and, hence, the relative importance of the two crops could be reversed in the future. This study compared production risks associated with turnip rape and oilseed rape in two climate-change scenarios, the high-emission A2 scenario and the low-emission B1 scenario, with or without changes in the length of the growing season. To compute future changes in temperature accumulation, observations were modified by the average of temperature increases simulated by 19 global climate models. Four plant-breeding scenarios were also included: a similar pace of yield improvements as recorded over recent years, halved or doubled rates of improvement, and no improvements (levelling off). The production risks were compared by analysing the yield-value changes under projected conditions (i.e., in different combinations of scenarios) on the basis of temperature- and plant-breeding-dependent changes in seed yield, oil content, and chlorophyll content. Both plant breeding and climate change already have alone the potential to change the balance between oilseed rape and turnip rape. When acting together the change will be more apparent and faster, but plant breeding will, however, play a more significant role in yield-trend changes than will climate change under northern conditions. If the current rate of plant-breeding improvements continues, only a 100°C increase in temperature sum during the growing season would result in domination of oilseed rape over turnip rape in Finland. This comparative analysis also indicated that strategies, including doubling of oilseed crop production area, are realistic if the climate change and plant breeding achievements facilitate cultivation of oilseed crops in more northern areas. If northern areas are taken into oilseed crop production the lifespan of turnip rape in Finnish field crop production could be extended. Nevertheless, a breeding strategy for northern conditions needs increased efforts focussed on oilseed rape.

Are there indications of climate change induced increases in variability of major field crops in the northernmost European conditions

As the northern hemisphere will experience the greatest increases in temperature and indications of climatic change are already visible in the north (in the 2000s average temperatures exceeded the long-term mean), we sought to establish if there are already signs of increased variability in yield and quality of the major field crops grown under the northernmost European growing conditions: spring and winter cereals (barley Hordeum vulgare L., oat Avena sativa L., wheat Triticum aestivum L., rye Secale cereale L.), spring rapeseed (turnip rape Brassica rapa L., oilseed rape B. napus L.), pea (Pisum sativum L.) and potato (Solanum tuberosum L.). We used long-term yield datasets of FAO for Finland (1960s to date) and MTT Agrifood Research Finland (MTT) Official Variety Trial datasets on yield and quality of major field crops in Finland since the 1970s. Yield variability was exceptionally high in the 1980s and 1990s, but previously and subsequently national yields were clearly more stable. No progressive increase in yield variability was recorded. No marked and systematic changes in variability of quality traits were recorded, except for rapeseed, which exhibited reduced variability in seed chlorophyll content. This may at least partly attribute to the differences in intensity of input use and thereby responsiveness of the crops before and after 1980 and 1990 decades. We also noted that in the 2000s average temperatures were higher than in earlier decades and this was the case for all months of the growing season except June, which represents, however, the most critical phase for yield determination in most of the field crops in Finland. Also in the 2000s precipitation increased in the first three months of the growing season and thereafter decreased, but without signs of significantly increased numbers of heavy showers (extreme rain events). Hence, in general constant, increased average temperatures during the growing seasons of the 2000s were identified, but with reduced yield variability, which was partly attributable to the diminished use of inputs, especially fertilisers.

Climate-induced overwintering challenges for wheat and rye in northern agriculture

Abstract Winters are typically harsh in the northernmost agricultural areas of Europe, and winter rye (Secale cereale L.) and wheat (Triticum aestivum L.) are the only winter grain crops that can be grown. However, climate change is projected to result in milder winters, which may enable cultivation of winter crops to a greater extent in the future than is possible today. In this study we aimed at identifying main temperature, precipitation events and characteristics that have resulted in past poor overwintering of rye and wheat in their current production areas in Finland. Using long-term (1970–2006), multi-location datasets, we compared our findings with the projected major changes attributable to climate change. Mixed models were used to estimate mutually comparable overwintering damage to all experiments and logistic regression was used to determine whether climatic parameters are related to high levels of overwintering damage. Severity of overwintering damage, and associated yield penalties, fluctuate considerably on a year-to-year basis and no consistent reduction in variability was recorded during the study period. Particularly for wheat, severity of winter damage in any one year was associated negatively with area sown in the following year. There was no evidence of consistent genetic improvements in winter hardiness, but rye was more winter hardy than wheat. Current risks associated with rye production related to low temperatures could be alleviated in the future, although overwintering damage currently enhanced by high autumn precipitation could increase due to climate change. For wheat, fluctuating conditions hampered overwintering, which may be an even harder challenge in future when weather variation is projected to increase and extreme weather events are projected to become more common.

Potential and realities of enhancing rapeseed- and grain legume-based protein production in a northern climate

Crop-based protein self-sufficiency in Finland is low. Cereals dominate the field cropping systems in areas that are also favourable for legumes and rapeseed. The present paper estimated the realistic potential for expanding protein crop production taking account of climatic conditions and constraints, crop rotation requirements, field sizes, soil types and likelihood for compacted soils in different regions. The potential for current expansion was estimated by considering climate change scenarios for 2025 and 2055. By using actual regional mean yields for the 2000s, without expecting any yield increase during the expansion period (due to higher risks of pests and diseases), potential production volumes were estimated. Since rapeseed, unlike grain legumes, is a not a true minor crop, its expansion potential is currently limited. Thus, most potential is from the introduction of legumes into cropping systems. The current 100000 ha of protein crops could be doubled, and areas under cultivation could reach 350000 and 390000 ha as a result of climate warming by 2025 and 2055, respectively. Such increases result mainly from the longer growing seasons projected for the northern cropping regions of Finland. Self-sufficiency in rapeseed could soon increase from 0·25 to 0·32, and then to 0·50 and 0·60 by 2025 and 2055, respectively. If legume production expands according to its potential, it could replace 0·50–0·60 of currently imported soybean meal, and by 2025 it could replace it completely. Replacement of soybean meal is suitable for ruminants, but it presents some problems for pig production, and is particularly challenging for poultry.

Crop responses to climate and socioeconomic change in northern regions

Climate, farmers’ actions and previous cultivation history influence regional crop yields and drive autonomous adaptation in time. Proceeding climate change will induce needs for various adaptation measures in the future, especially in the northern regions. We investigated how farms take advantage of novel opportunities in Finland as dictated by the biophysical environment, farmer experience and knowledge, and the dynamics of the socioeconomic environment. Using Finland as a case, we aimed to characterize the relation of regional climate and yield development of the four major cereal crops since 1965 and of spring rape since 1978. Yields in the northernmost regions were most responsive to growing season temperature sum and precipitation. However, yield levels in southern relative to northern and eastern areas have polarized through the period, which might be an indication of a socioeconomic rather than a climate-related response. As socioeconomic factors can be more deterministic for targeting autonomous adaptation on farms, regionally planned proactive adaptation strategies are needed to prepare for long-term changes such as the climate change.

Improving farming systems in northern Europe

Abstract Northern growing conditions as they are described here are exceptional as they combine many conditions and features in such a way that is only typical for the globally northernmost, high latitude agricultural regions. Such conditions combine, e.g. harsh winters, long days in growing season, rapidly increasing but generally cool mean temperatures, risk of night frosts in early and late growing season, early summer drought and risk of abundant precipitation close to harvest. Successful crop production under such conditions requires specific adaptation mechanisms to cope with climatic exceptionalities and handicaps. But they are, however, only part of the challenge that the northern agricultural systems face as also substantial fluctuations in climatic conditions that occur within and among years and seasons call for specific means to improve yield stability and the environmental footprint of agriculture. Crop physiological understanding provides essential basic tools to develop cropping systems so that they can better meet the increasingly complex sustainability goals set for present and future production: meaning not only environmental sustainability but also in socioeconomical meaning. This chapter characterizes the prevailing growing conditions and means to cope with them in cereal-based cropping systems and envisages some primary changes in conditions that call for additional adaptation strategies and means in the future.