Input of nitrogen from N2 fixation to northern grasslands

Forage legumes form N2-fixing symbioses with rhizobia and may thus make substantial contributions to the N pool in grasslands. However, to optimize their use as sources of N, it is important to elucidate the effects of management factors that influence their N2 fixation rates, and to develop convenient methods for measuring N2 fixation quickly and reliably. An analysis of published data on N2 fixation in the field showed that lucerne (Medicago sativa L.), red clover (Trifolium pratense L.), and white clover (T. repens L.) grown in mixtures with grasses derived most of their N from N2 fixation, irrespective of geographic location and management practices – and despite large inter-annual variations in legume dry matter yield (kg ha-1 year-1). Consequently, there were strong correlations between legume dry matter yield and amounts of N2 fixed (kg N ha-1 year-1), which can be used very simply to obtain estimates of N2 fixation in these legumes. In experimental grassland plots where the species richness of neighbouring vegetation was varied, alsike clover (T. hybridum L.), red clover, and white clover consistently derived at least half of their N from N2 fixation, measured by the 15N natural abundance (NA) method using three different reference plants. This method is sensitive to the degree of discrimination against 15N in the N2-fixing plant (B value) and the choice of reference plant. B values were therefore established for each of the three clover species in symbioses with different Scandinavian Rhizobium leguminosarum bv. trifolii genotypes. In red clover, reductions following cutting in the activity of the N2-fixing enzyme, nitrogenase, and the rate of shoot regrowth were dependent on the cutting height. The recovery in nitrogenase activity after cutting followed the rate of leaf area increment, which confirms the correlation between N2 fixation and growth found in field experiments. The results of the work underlying this thesis show that perennial forage legumes growing in grasslands are highly dependent on N2 fixation. Awareness of this should facilitate the development of resource-efficient management regimes for northern grasslands

Management of biomass resources within the crop rotation for eco-functional intensification on stockless organic farms

There is an increased competition for land used in food or energy production (Harvey & Pilgrim, 2011) that necessitates a functional intensification. Can a cropping system be designed to produce high-quality food crops, biogas and fertilizer in the same cropping season, while minimizing both the negative impact on the local aquatic environment and greenhouse gas emissions? The present study investigates this challenge, focusing on crop nitrogen (N) supply and the production of renewable energy on stockless organic farms

Svenska ekologiska linser

Linser har låg stjälkstyrka och svag konkurrensförmåga och blir därför lätt övervuxna av ogräs, speciellt i ekologisk produktion. Skörden försvåras också ofta på grund av liggsäd, det vill säga att plantorna lägger sig ner mot marken. Genom att samodla linser med spannmål, till exempel havre, uppnås effektivare konkurrens mot ogräs samtidigt som linserna får stöd, så att problemen med liggsäd undviks

Limiting livestock production to pasture and by-products in a search for sustainable diets

A method was developed for designing ‘fair’ diets (not using more than globally available arable land percapita) and for assessing the sustainability of such diets. The diets were based on the principle of ‘ecological leftovers’ for livestock production, i.e. raising livestock on pasture and by-products not suitable for or wanted by humans. The method was applied to Sweden using three different scenarios for livestock production, all taking the starting point that semi-natural pastures should be grazed by ruminants for reasons of biodiversity conservation. The scenarios also included differing use of by-products (from crop production and food processing) to either boost milk production (I-Milk scenario) or produce eggs and pig meat (E-Milk and Suckler scenarios). In I-Milk, milk and meat were produced in intensive systems in which dairy cows and their offspring only grazed to a limited extent, resulting in the human diet containing recommended levels of dairy products (350 ml milk per day) and meat twice a week. Milk could also be exported. In E-Milk, pasture was used more for dairy cows and their offspring, resulting in fewer animals and less milk (150 ml milk per day) and four servings of meat per week. In the Suckler scenario, pasture was grazed by suckler herds providing no milk but meat four times per week. The environmental impacts of the diets were assessed using the planetary boundaries framework. The results showed substantially lower environmental impacts compared with the average current Swedish diet, but the strict absolute climate boundary and the N and P input boundaries were still exceeded for all diets. The approach adopted, of letting the ecological resource capacity act as the constraining factor for livestock production, is in line with agroecology principles and efficient use of land to improve food security,and could be useful in discussions about sustainable consumption of animal products

Designing a future food vision for the Nordics through a participatory modeling approach

International audienceAbstractThe development of future food systems will depend on normative decisions taken at different levels by policymakers and stakeholders. Scenario modeling is an adequate tool for assessing the implications of such decisions, but for an enlightened debate, it is important to make explicit and transparent how such value-based decisions affect modeling results. In a participatory approach working with five NGOs, we developed a future food vision for the Nordic countries (Denmark, Finland, Norway and Sweden) through an iterative process of defining the scenario, modeling, and revising the scenario, until a final future food vision was reached. The impacts on food production, land use, and greenhouse gas emissions, and the resulting diets in the food vision, were modeled using a mass flow model of the food system. The food vision formulated was an organic farming system where food is produced locally and livestock production is limited to “leftover streams,” i.e., by-products from food production and forage from pastures and perennial grass/clover mixtures, thus limiting food-feed competition. Consumption of meat, especially non-ruminant meat, was substantially reduced compared with current consumption in the Nordic countries (− 81%). An estimated population of 37 million people could be supplied with the scenario diet, which uses 0.21 ha of arable land and causes greenhouse gas emissions of 0.48 tCO2e per diet and year. The novelty of this paper includes advancing modeling of sustainable food systems by using an iterative process for designing future food visions based on stakeholder values, which enables results from multidisciplinary modeling (including agronomy, environmental system analysis, animal and human nutrition) to be fed back into the decision-making process, providing an empirical basis for normative decisions and a science-based future vision of sustainable food systems

Less meat, more legumes: prospects and challenges in the transition toward sustainable diets in Sweden

The Western diet is characterized by high meat consumption, which negatively affects the environment and human health. Transitioning toward eating more plant-based products in Western societies has been identified as a key instrument to tackle these problems. However, one potential concern is that radically reducing meat in the current diet might lead to deficiencies in nutritional intake. In this paper, we explore a scenario in which meat consumption in Sweden is reduced by 50% and replaced by domestically grown grain legumes. We quantify and discuss the implications for nutritional intake on population level, consequences for agricultural production systems and environmental performance. The reduction in meat consumption is assumed to come primarily from a decrease in imported meat. We use data representing current Swedish conditions including the Swedish dietary survey, the Swedish food composition database, Statistics Sweden and existing life cycle assessments for different food items. At population level, average daily intake of energy and most macro- and micro-nutrients would be maintained within the Nordic Nutrition Recommendations after the proposed transition (e.g., for protein, fat, zinc, vitamin B12 and total iron). The transition would also provide a considerable increase in dietary fiber and some increase in folate intake, which are currently below the recommended levels. The transition scenario would increase total area of grain legume cultivation from 2.2% (current level) to 3.2% of Swedish arable land and is considered technically feasible. The climate impact of the average Swedish diet would be reduced by 20% and the land use requirement by 23%. There would be a net surplus of approximately 21,500 ha that could be used for bioenergy production, crop production for export, nature conservation, etc. Implementation of this scenario faces challenges, such as lack of suitable varieties for varying conditions, lack of processing facilities to supply functional legume-based ingredients to food industries and low consumer awareness about the benefits of eating grain legumes. In sum, joint efforts from multiple actors are needed to stimulate a decrease in meat consumption and to increase cultivation and use of domestically grown grain legumes