Grain legume production offers multiple environmental benefits and can enhance sustainability of European farming, but their production area is declining constantly. Grain legume competitiveness is frequently constrained by lower gross margins compared to agronomically suitable cropping alternatives, but it can be improved by appreciating their ability to increase yield of subsequent crop(s) and, potentially, to reduce input requirements (fertiliser, biocide, tillage). Information on the magnitude of grain legume pre-crop effects is diverse and has not been synthesised for European agriculture. This paper reviews research on pre-crop benefits to yield and input requirements of subsequent crops, and the farm-economic profitability of grain legumes in European cropping systems. This includes an analysis of the magnitude of pre-crop benefits to cereal yields measured in 29 experiments in Europe; and 19 studies on grain legume gross margins ranging from crop to cropping system level are assessed. In the available studies, yield benefits of legumes to subsequent crops are highest under low nitrogen fertilisation to subsequent crops and fertilisation can be reduced by 60kgNha−1 on average under maintenance of acceptable yields. With the aim at maximising yield potential, nitrogen fertilisation following grain legumes can be reduced by 23–31kgha−1, and cereal yields are mostly 0.5–1.6Mgha−1 higher than after cereal pre-crops. With adequate estimates of pre-crop benefits, gross margins of full crop rotations can better assess grain legume competitiveness. In the studies reviewed, 35 of 53 modelled crop rotations with grain legumes were competitive with comparable non-legume rotations. Grain legume rotations were more competitive under conservation tillage systems if gross margin calculations accounted for cost savings arising from adjusted machinery requirements. In conclusion, grain legume pre-crop value is a crucial component of their farm-economic profitability in European cropping systems, but further experimental research is required to ascertain its magnitude. Expanding profitability measures to consider pre-crop effects substantially increases the number of situations where grain legumes can compete with cereals, and has a small positive effect on their competitiveness with alternative break crops. Besides a better consideration of the pre-crop value, further genetic and agronomic improvement in legume cropping, supportive market development, and policy support are required if Europe is to utilise environmental benefits of legumes and increase the sustainability of its farming

Agricultural intensification increased crop productivity but simplified production with lower diversity of cropping systems, higher genetic uniformity, and a higher uniformity of agricultural landscapes. Associated detrimental effects on the environment and biodiversity as well as the resilience and adaptability of cropping systems to climate change are of growing concern. Crop diversification may stabilize productivity of cropping systems and reduce negative environmental impacts and loss of biodiversity, but a shared understanding of crop diversification including approaches towards a more systematic research is lacking. Here, we review the use of ‘crop diversification’ measures in agricultural research. We (i) analyse changes in crop diversification studies over time; (ii) identify diversification practices based on empirical studies; (iii) differentiate their use by country, crop species and experimental setup and (iv) identify target parameters to assess the success of diversification. Our main findings are that (1) less than 5% of the selected studies on crop diversification refer to our search term ‘diversification’; (2) more than half of the studies focused on rice, corn or wheat; (3) 76% of the experiments were conducted in India, USA, Canada, Brazil or China; (4) almost any arable crop was tested on its suitability for diversification; (5) in 72% of the studies on crop diversification, at least one additional agronomic measure was tested and (6) only 45% of the studies analysed agronomic, economic and ecological target variables. Our findings show the high variability of approaches to crop diversification and the lack of a consistent theoretical concept. For better comparability and ability to generalise the results of the different primary studies, we suggest a novel conceptual framework. It consists of five elements, (i) definition of the problem of existing farming practices and the potential need for diversification, (ii) characterisation of the baseline system to be diversified, (iii) definition of the scale and target area, (iv) description of the experimental design and target variables and (v) definition of the expected impacts. Applying this framework will contribute to utilizing the benefits of crop diversification more efficiently.

Methods are needed for the design and evaluation of cropping systems, in order to test the effects of introducing or reintroducing crops into rotations. The interaction of legumes with other crops (rotational effects) requires an assessment at the cropping system scale. The objective of this work is to introduce a cropping system framework to assess the impacts of changes in cropping systems in a participatory approach with experts, i.e., the integration of legumes into crop rotations and to demonstrate its application in two case studies. The framework consists of a rule-based rotation generator and a set of algorithms to calculate impact indicators. It follows a three-step approach: (i) generate rotations, (ii) evaluate crop production activities using environmental, economic and phytosanitary indicators, and (iii) design cropping systems and assess their impacts. Experienced agronomists and environmental scientists were involved at several stages of the framework development and testing in order to ensure the practicability of designed cropping systems. The framework was tested in Västra Götaland (Sweden) and Brandenburg (Germany) by comparing cropping systems with and without legumes. In both case studies, cropping systems with legumes reduced nitrous oxide emissions with comparable or slightly lower nitrate-N leaching, and had positive phytosanitary effects. In arable systems with grain legumes, gross margins were lower than in cropping systems without legumes despite taking pre-crop effects into account. Forage cropping systems with legumes had higher or equivalent gross margins and at the same time higher environmental benefits than cropping systems without legumes. The framework supports agronomists to design sustainable legume-supported cropping systems and to assess their impacts

Europe’s agriculture is highly specialized, dependent on external inputs and responsible for negative environmental impacts. Legume crops are grown on less than 2 % of the arable land and more than 70 % of the demand for protein feed supplement is imported from overseas. The integration of legumes into cropping systems has the potential to contribute to the transition to a more resource-efficient agriculture and reduce the current protein deficit. Legume crops influence the production of other crops in the rotation making it difficult to evaluate the overall agronomic effects of legumes in cropping systems. A novel assessment framework was developed and applied in five case study regions across Europe with the objective of evaluating trade-offs between economic and environmental effects of integrating legumes into cropping systems. Legumes resulted in positive and negative impacts when integrated into various cropping systems across the case studies. On average, cropping systems with legumes reduced nitrous oxide emissions by 18 % and 33 % and N fertilizer use by 24 % and 38 % in arable and forage systems, respectively, compared to systems without legumes. Nitrate leaching was similar with and without legumes in arable systems and reduced by 22 % in forage systems. However, grain legumes reduced gross margins in 3 of 5 regions. Forage legumes increased gross margins in 3 of 3 regions. Among the cropping systems with legumes, systems could be identified that had both relatively high economic returns and positive environmental impacts. Thus, increasing the cultivation of legumes could lead to economic competitive cropping systems and positive environmental impacts, but achieving this aim requires the development of novel management strategies informed by the involvement of advisors and farmers.