Helena Kahiluoto

Promotion of AM utilization through reduced P fertilization 2. Field studies

The hypothesis of this study was that cumulative P fertilization decreases the contribution of arbuscular mycorrhiza (AM) to crop growth and nutrient uptake in Northern European field conditions. The modes of action of P fertilization were evaluated through effects on mycorrhization, crop dependence on AM, and AM fungal (AMF) community. Field studies were carried out within long-term experiments on soils with low and intermediate initial content of extractable P, where no P fertilization and 45 kg ha−1 a−1 P were applied for 20 years. AM effectiveness in terms of growth and nutrient uptake of flax, red clover and barley, percentage root length colonized by AMF, P response of flax, and spore densities and species composition of the AMF communities, were assessed. In the soil with low initial P supply, cumulative P fertilization decreased AM contribution to crop growth and nutrient uptake. The higher AM effectiveness in soil with no added P compensated the cumulative P fertilization (soil PH2O 2.5 v. 9.5 mg kg−1) for flax, but not completely for clover. In contrast, barley obtained no benefit from AM at harvest and only a slight benefit from cumulated P. In the soil with intermediate initial P supply, AM reduced growth of flax and barley, especially with no added P, and no response to AM was obtained on clover due to retarded mycorrhization. Cumulative P fertilization reduced yield losses of flax by AM (PH2O 18.8 v. 5.4 mg kg−1), because fertilization inhibited mycorrhization. In both soils, root colonization and spore density were decreased by cumulative P fertilization, but no changes in AMF species composition were observed.

Creation of a non-mycorrhizal control for a bioassay of AM effectiveness

γ-irradiation of soil by 10 and 3 kGy, and the use of a myc− mutant. The methods were examined on clay and loam. Two management histories were included with both soils to study the ability of the methods to differentiate AM effectiveness. For each soil type, two pot experiments were conducted in field soil, one to investigate the effects of the methods on soil nutrient status, and the other to study the effects on mycorrhization and plant response. The test plants, flax (Linum usitatissimum) and pea (Pisum sativum) myc+ and myc− mutants, were grown in 1-l pots for 4 weeks in a growth chamber. To test the ability of the bioassay to reflect differences in AM effectiveness in the field, the mutants and benomyl were also studied in the field from which the loam for the pot experiments was obtained. The bioassay accurately represented the situation in the field and the use of benomyl appeared to be the most appropriate method currently available. The advantages were the ability to use a test plant responsive to AM, the use of less elevated nutrient concentrations than with irradiation, and thus the possibility to use untreated soil as the mycorrhizal treatment. The pea mutants proved unresponsive to AM, and reinoculation to irradiated soil resulted in only half the colonization rate in untreated soil. Benomyl may, however, lead to an underestimation of AM effectiveness because the control is not totally non-mycorrhizal. Its use also carries with it health and environmental risks.

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.

Modelling shifts in agroclimate and crop cultivar response under climate change.

This paper aims: (i) to identify at national scale areas where crop yield formation is currently most prone to climate-induced stresses, (ii) to evaluate how the severity of these stresses is likely to develop in time and space, and (iii) to appraise and quantify the performance of two strategies for adapting crop cultivation to a wide range of (uncertain) climate change projections. To this end we made use of extensive climate, crop, and soil data, and of two modelling tools: N-AgriCLIM and the WOFOST crop simulation model. N-AgriCLIM was developed for the automatic generation of indicators describing basic agroclimatic conditions and was applied over the whole of Finland. WOFOST was used to simulate detailed crop responses at four representative locations. N-AgriCLIM calculations have been performed nationally for 3829 grid boxes at a 10 × 10 km resolution and for 32 climate scenarios. Ranges of projected shifts in indicator values for heat, drought and other crop-relevant stresses across the scenarios vary widely – so do the spatial patterns of change. Overall, under reference climate the most risk-prone areas for spring cereals are found in south-west Finland, shifting to south-east Finland towards the end of this century. Conditions for grass are likely to improve. WOFOST simulation results suggest that CO2 fertilization and adjusted sowing combined can lead to small yield increases of current barley cultivars under most climate scenarios on favourable soils, but not under extreme climate scenarios and poor soils. This information can be valuable for appraising alternative adaptation strategies. It facilitates the identification of regions in which climatic changes might be rapid or otherwise notable for crop production, requiring a more detailed evaluation of adaptation measures. The results also suggest that utilizing the diversity of cultivar responses seems beneficial given the high uncertainty in climate change projections.

Promotion of utilization of arbuscular mycorrhiza through reduced P fertilization 1. Bioassays in a growth chamber

The study investigated the possibilities of promoting utilization of arbuscular mycorrhiza (AM) in crop P nutrition in Northern European conditions by decreasing P fertilization. The effect of two contrasting long-term P fertilization regimes on fungal (AMF) infectivity, on contribution of AM to crop growth and nutrient uptake, and on P and N responses was investigated in bioassays in a growth chamber with the original field soil. A control with suppressed AM was successfully created by benomyl application. Functional properties of the field AMF communities were compared after back- and cross-inoculation to the irradiated field soils. The two long-term field experiments that were utilized represented clay and loam soils and P levels from low to high. The results show that annual dressings of soluble inorganic P fertilizers, even in moderate amounts, decrease the infectivity and effectiveness of AMF communities of Northern European field soils. The functional properties of the communities also seem to adapt to the different P regimes. Moderate P fertilization generally decreases the total AM benefit to crops and can lead to growth depression by AM. At the lower end of the P supply of Nordic field soils, however, AM may at least transiently impose a net cost to crops with a high P demand such as flax or with a low dependency on AM such as barley. The impact of the P history on AM was not related to plant P nutrition only. Mycorrhization can be immediately improved by omitting P application.

Climate variability and change in the Central Rift Valley of Ethiopia: challenges for rainfed crop production

Ethiopia is one of the countries most vulnerable to the impacts of climate variability and change on agriculture. The present study aims to understand and characterize agro-climatic variability and changes and associated risks with respect to implications for rainfed crop production in the Central Rift Valley (CRV). Temporal variability and extreme values of selected rainfall and temperature indices were analysed and trends were evaluated using Sens slope estimator and Mann–Kendall trend test methods. Projected future changes in rainfall and temperature for the 2080s relative to the 1971–90 baseline period were determined based on four General Circulation Models (GCMs) and two emission scenarios (SRES, A2 and B1). The analysis for current climate showed that in the short rainy season (March–May), total mean rainfall varies spatially from 178 to 358 mm with a coefficient of variation (CV) of 32–50%. In the main (long) rainy season (June–September), total mean rainfall ranges between 420 and 680 mm with a CV of 15–40%. During the period 1977–2007, total rainfall decreased but not significantly. Also, there was a decrease in the number of rainy days associated with an increase (statistically not significant) in the intensity per rainfall event for the main rainy season, which can have implications for soil and nutrient losses through erosion and run-off. The reduced number of rainy days increased the length of intermediate dry spells by 0·8 days per decade, leading to crop moisture stress during the growing season. There was also a large inter-annual variability in the length of growing season, ranging from 76 to 239 days. The mean annual temperature exhibited a significant warming trend of 0·12–0·54 °C per decade. Projections from GCMs suggest that future annual rainfall will change by +10 to -40% by 2080. Rainfall will increase during November–December (outside the growing season), but will decline during the growing seasons. Also, the length of the growing season is expected to be reduced by 12–35%. The annual mean temperature is expected to increase in the range of 1·4–4·1 °C by 2080. The past and future climate trends, especially in terms of rainfall and its variability, pose major risks to rainfed agriculture. Specific adaptation strategies are needed for the CRV to cope with the risks, sustain farming and improve food security.

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.

Mitigation of Climate Change to Enhance Food Security: An Analytical Framework

Carbon trading between the industrial and developing world offers an opportunity to maintain global warming below critical limits and to promote global climate equity. The potential has not been realised in sub-Saharan Africa, which is most vulnerable in terms of food security in a changing climate. The objective of this study was to create an analytical framework to identify determining factors to enhance food security through mitigation of climate change. The potential for carbon trading between Finland and Ethiopia was the studied case. A hypothetical analytical framework was created based on literature. It was validated and developed through in-depth interviews and focus group discussions of global and national actors in Finland and Ethiopia and local actors from two contrasting Ethiopian regions. The qualitative analysis highlighted increasing agricultural productivity and facilitating internal national markets as the main means to enhance food security through mitigation of climate change, triggered by generating carbon income. The socio-economic determinants of major importance appeared to be multi-level coherence of policy and action, early access to financial incentives, quality of governance, infrastructure for internal markets, population density, land tenure systems and knowledge about carbon markets, mitigation options and their verification. The main agro-ecological determinants were local hydrology, management history and present land management. The immediate attention of decision-makers is drawn to policy coherence and development of funding, verification and knowledge on carbon sequestration through agricultural management. The analytical framework is concluded to be valid for interaction between industrial countries and specific national and local SSA contexts.

Potential of energy and nutrient recovery from biodegradable waste by co-treatment in Lithuania

Biodegradable waste quantities in Lithuania and their potential for the co-treatment in renewable energy and organic fertilizer production were investigated. Two scenarios were formulated to study the differences of the amounts of obtainable energy and fertilizers between different ways of utilization. In the first scenario, only digestion was used, and in the second scenario, materials other than straw were digested, and straw and the solid fraction of sewage sludge digestate were combusted. As a result, the amounts of heat and electricity, as well as the fertilizer amounts in the counties were obtained for both scenarios. Based on this study, the share of renewable energy in Lithuania could be doubled by the co-treatment of different biodegradable materials

Understanding biorefining efficiency--the case of agrifood waste.

The aim of this study was to determine biorefining efficiency according to the choices made in the entire value chain. The importance of the share of biomass volume biorefined or products substituted was investigated. Agrifood-waste-based biorefining represented the case. Anticipatory scenarios were designed for contrasting targets and compared with the current situation in two Finnish regions. Biorefining increases nutrient and energy efficiency in comparison with current use of waste. System boundaries decisively influence the relative efficiency of biorefining designs. For nutrient efficiency, full exploitation of biomass potential and anaerobic digestion increase nutrient efficiency, but the main determinant is efficient substitution for mineral fertilisers. For energy efficiency, combustion and location of biorefining close to heat demand are crucial. Regional differences in agricultural structure, the extent of the food industry and population density have a major impact on biorefining. High degrees of exploitation of feedstock potential and substitution efficiency are the keys.