a b s t r a c tGrain 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 60 kg N ha −1 on average under maintenance of acceptable yields. With the aim at maximising yield potential, nitrogen fertilisation following grain legumes can be reduced by 23-31 kg ha −1 , and cereal yields are mostly 0.5-1.6 Mg ha −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.
Sustainable development of agriculture is at the core of agricultural policy debates in Europe. There is a consensus that diversification of cropping would support sustainable development. However, a reduction in legume cultivation has been observed in the EU during the last decades. This decline has induced, in turn, a deficit of proteins and a reduction of ecosystem services provided by legumes. Therefore, we analysed the mechanisms that shape agricultural systems to identify leverage points for reviving European legume production. Specifically, we reviewed the factors that affect the market and non-market value of legumes and the relevant agricultural policies. We characterized the decline in legume cropping as an outcome of the dominance of economic forces that favour specialization of production systems over diversification. We found that the value of market outputs of legumes per unit area is relatively low and volatile, with a 25-78 % variation in pea gross margins, which reduces market competitiveness. We observed that the value of systeminternal outputs of legumes such as the nitrogen fixed, of 130 to 153 kg N ha; crop protection services that reduce agrochemical costs, by 20-25 % in cereals; and yield enhancements of subsequent crops, of 0.2 to 1.6 t ha −1 in cereals, are often underestimated. In addition, markets fail to translate external effects of legumes such as biodiversity enhancement, reduction in emissions, of up to 50 % in N 2 O, and soil improvements into economic benefits. Current policies support legumes through selected mechanisms such as ecological focus areas, agri-environmental programmes and sparse coupled support measures. Domestic cultivation of legumes could be supported through trade policies such as import restrictions on genetically modified soybean or new mechanisms to appreciate non-market outputs including payments for ecosystem services and carbon markets. In addition, development of new value chains, niche markets, scaling-up of plant breeding efforts and dissemination of information is required.
Legume-based green manures (LGMs) are crops that are grown with the specific purpose of improving soil quality and consequently the long-term productivity of crops. Although the traditional focus has been on the supply of nitrogen (N) to the system, they have a wide range of potential benefits that include improving soil quality, reducing soil erosion and increasing the biodiversity of farmland. LGMs are a key component of organic farming systems where the use of synthetic N fertilizers is not permitted. However, increases in the cost of inputs, concerns about environmental impacts of intensive use of agrochemicals, and the recently announced measures for the 'greening' of the European Common Agricultural Policy have led to renewed interest in the use of LGMs more widely. In Europe, the legumes in LGMs may be annual or perennial plants, grown on their own or more often as part of crop mixtures with a range of other crop types such as grasses or brassicas. The legumes most commonly grown are the clovers (Trifolium spp.), particularly red and white clover. Other legumes that may be grown to suit particular local goals or constraints include Medicago spp. (lucerne (alfalfa) and black medic), trefoils (Lotus spp.), vetches (Vicia spp.), lupins (Lupinus spp.), other minor forage legumes and grain legumes. To maximize fertility building in organic farming systems, LGMs are grown in place of cash crops for some of the crop rotation. In more intensive systems, LGMs may be grown for short periods between phases of regular crop production. This chapter reviews the use of LGMs in Europe and considers factors that affect N fixation in them and the transfer of fixed N to following crops. It examines how they can be integrated into practical rotational cropping systems and whether the economics of this makes the use of LGMs profitable. However, LGMs will not be agronomically or economically viable in all systems, and in these cases other types of green manures may be more appropriate. As demand for multifunctional agricultural systems grows, and is increasingly required by European agricultural policies, so does the potential for greater use of LGMs.
Regional impact studies are needed to explore possible adaptation options to climate change. We estimated impacts and adaptation options for future scenarios that feature different assumptions regarding climate, cropping pattern and access to irrigation with two bio-economic farm models. Farm profit, soil organic matter balance and labor input are used as indicators of farm performance. The difference between the baseline and the alternative configurations computed by models is referred as adaptation potential, indicative of the adaptation options including the corresponding changes in cropping patterns. Our results show that as long as there is sufficient access to irrigation water, there is little incentive to change current practices, as farming is at the economic optimum, has a positive soil organic matter balance and labor requirements can be met. Conversely, if irrigation is no longer possible, drastic impacts occur, causing a need to sustainably adjust on-going farm practices. Adaptation through changed crop selection reduced losses to some extent. We conclude that the use of bio-economic models can assist in evaluating the qualitative findings of participatory studies by quantitatively assessing possible climate change impacts and adaptation measures. Strong impacts of climate change, however, cannot be offset by changes in cropping patterns and need further adaptation measures.
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