European grassland-based livestock production systems face the challenge of producing more meat and milk to meet increasing world demands and to achieve this using fewer resources. Legumes offer great potential for achieving these objectives. They have numerous features that can act together at different stages in the soil–plant–animal–atmosphere system, and these are most effective in mixed swards with a legume proportion of 30–50%. The resulting benefits include reduced dependence on fossil energy and industrial N-fertilizer, lower quantities of harmful emissions to the environment (greenhouse gases and nitrate), lower production costs, higher productivity and increased protein self-sufficiency. Some legume species offer opportunities for improving animal health with less medication, due to the presence of bioactive secondary metabolites. In addition, legumes may offer an adaptation option to rising atmospheric CO2 concentrations and climate change. Legumes generate these benefits at the level of the managed land-area unit and also at the level of the final product unit. However, legumes suffer from some limitations, and suggestions are made for future research to exploit more fully the opportunities that legumes can offer. In conclusion, the development of legume-based grassland–livestock systems undoubtedly constitutes one of the pillars for more sustainable and competitive ruminant production systems, and it can be expected that forage legumes will become more important in the future.

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Potential of legume-based grassland–livestock systems in Europe: a review

Biogas from anaerobic digestion processes: Research updates

Mixed-species versus monocultures in plantation forestry: Development, benefits, ecosystem services and perspectives for the future

The expected move towards more sustainable crop-livestock systems implies wider cultivation of perennial forage legumes. Alfalfa (Medicago sativa subsp. sativa) is the main perennial legume in most temperate regions, especially where farm systems rely largely on forage conservation. White clover (Trifolium repens) and red clover (Trifolium pratense) are dominant in specific regions and farm systems. Although breeding progress for disease and insect resistance has been achieved, these crops have shown lower rates of genetic gain for yield than major grain crops, owing to lower breeding investment, longer selection cycles, impossibility to capitalize on harvest index, outbreeding mating systems associated with severe inbreeding depression, and high interaction of genotypes with cropping conditions and crop utilizations. Increasing yield, persistence, adaptation to stressful conditions (drought; salinity; grazing) and compatibility with companion grasses are major breeding targets. We expect genetic gain for...

Achievements and Challenges in Improving Temperate Perennial Forage Legumes

Agricultural ecosystems produce food, fiber, and nonmarketed ecosystem services (ES). Agriculture also typically involves high negative external costs associated with, for example, fossil fuel use. We estimated, via field-scale ecological monitoring and economic value-transfer methods, the market and nonmarket ES value of a combined food and energy (CFE) agro-ecosystem that simultaneously produces food, fodder, and bioenergy. Such novel CFE agro-ecosystems can provide a significantly increased net crop, energy, and nonmarketed ES compared with conventional agriculture, and require markedly less fossil-based inputs. Extrapolated to the European scale, the value of nonmarket ES from the CFE system exceeds current European farm subsidy payments. Such integrated food and bioenergy systems can thus provide environmental value for money for European Union farming and nonfarming communities.

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The Value of Producing Food, Energy, and Ecosystem Services within an Agro-Ecosystem

Legumes play a crucial role in nitrogen supply to grass-legume mixtures for ruminant fodder. To quantify N transfer from legumes to neighbouring plants in multi-species grasslands we established a grass-legume-herb mixture on a loamy-sandy site in Denmark. White clover (Trifolium repens L.), red clover (Trifolium pratense L.) and lucerne (Medicago sativa L.) were leaf-labelled with 15N enriched urea during one growing season. N transfer to grasses (Lolium perenne L. and xfestulolium), white clover, red clover, lucerne, birdsfoot trefoil (Lotus corniculatus L.), chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), salad burnet (Sanguisorba minor L.) and caraway (Carum carvi L.) was assessed. Neighbouring plants contained greater amounts of N derived from white clover (4.8 g m-2) compared with red clover (2.2 g m-2) and lucerne (1.1 g m-2). Grasses having fibrous roots received greater amounts of N from legumes than dicotyledonous plants which generally have taproots. Slurry application mainly increased N transfer from legumes to grasses. During the growing season the three legumes transferred approximately 40 kg N ha-1 to neighbouring plants. Below-ground N transfer from legumes to neighbouring plants differed among nitrogen donors and nitrogen receivers and may depend on root characteristics and regrowth strategies of plant species in the multi-species grassland.

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Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland

N2-fixation and residual N effect of four legume species and four companion grass species

Provision of an adequate mineral supply in the diets of ruminants fed mainly on grassland herbage can present a challenge if mineral concentrations are suboptimal for animal nutrition. Forage herbs may be included in grassland seed mixtures to improve herbage mineral content, although there is limited information about mineral concentrations in forage herbs. To determine whether herbs have greater macro- and micromineral concentrations than forage legumes and grasses, we conducted a 2-year experiment on a loamy-sand site in Denmark sown with a multi-species mixture comprised of three functional groups (grasses, legumes and herbs). Herb species included chicory (Cichorium intybus L.), plantain (Plantago lanceolata L.), caraway (Carum carvi L.) and salad burnet (Sanguisorba minor L.). We also investigated the effect of slurry application on the macro- and micromineral concentration of grasses, legumes and herbs. In general, herbs had greater concentrations of the macrominerals P, Mg, K and S and the microminerals Zn and B than grasses and legumes. Slurry application indirectly decreased Ca, S, Cu and B concentrations of total herbage because of an increase in the proportion of mineral-poor grasses. Our study indicates that including herbs in forage mixtures is an effective way of increasing mineral concentrations in herbage.

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Forage herbs improve mineral composition of grassland herbage

Introduction
Cut grassland systems usually have high N efficiency and consequently low nitrate leaching, whereas the introduction of grazing animals increases the loss potential dramatically (Jarvis, 2000). It has been demonstrated that nitrate leaching from unfertilised grass-clover swards is lower than from mineral-N fertilised swards grazed by cattle. The possible explanation for this is that the N2 fixation by pasture legumes is regulated by a natural feedback mechanism driven by soil inorganic N levels. The feedback mechanism acts as a limit to N inputs from legumes and consequently regulates the potential for N losses (Ledgard, 2001). In this paper we report 5 years (1997-2002) of nitrate leaching from four cropping sequences with different grassland frequency and management for both unfertilised grass-clover and fertilised monoculture grass. Furthermore, one year of N2 fixation in 1, 2 and 8-year-old grass-clover pastures is reported.

Materials and methods
Four cropping sequences (long-term grazed, long-term cut, cereals followed by 1 and 2 year grazed leys) were established for both unfertilised grass-clover (perennial ryegrass [Lolium perenne L.]/white clover [Trifolium repens L.]) and fertilised perennial ryegrass (300 kg N ha-1). Each plot was equipped with ceramic suction cups and nitrate leaching was estimated during 1997-2002 as described by Eriksen (2001). In 2001, N2 fixation was estimated in 1, 2 and 8-year-old grass-clover pastures using an enriched 15N-dilution method as described by Vinther and Jensen (2000). In the cropping sequence with cut grass, annual herbage production was determined during 1994-2001. 

Results and discussion
Nitrate leaching from grazed unfertilised grass-clover was always considerably lower than from grazed fertilised ryegrass. In production years 6-8, losses from grass-clover were only 9-13% of the comparable losses from ryegrass, confirming the findings of others in systems with grazing cattle. This indicates a lowering of N inputs in grazed grass-clover swards with increasing age, since many data have suggested that nitrate leaching from grass systems are similar, at similar total N inputs, regardless of the source of N (Ledgard, 2001). 

N2-fixation was lower in 8-year-old swards compared with fully established 2-year-old swards as a consequence of lower dry matter production, lower clover content and a lower proportion of clover-N derived from the atmosphere. During the lifetime of the old grass-clover swards, N2-fixation dropped from 260 kg N ha-1 in the first three years (Eriksen, 2001) to 115 kg N in production year 8, in contrast to the fertilised grass sward that received 300 kg N ha-1 in all years. Thus, over the years a considerable difference between sward types has built up which may, at least partly, explain the differences in nitrate leaching. Following year 8, leaching from ryegrass exceeded that of grass-clover by on average 108 kg N ha-1.

The deposition of dung and urine by cows during grazing is unknown, as one herd (for practical and economic reasons) grazed all plots. However, some relationship is expected between grass production and manure deposition simply because cows graze more in highly productive plots which inevitably leads to higher deposition. As dry matter production was maintained in older cut ryegrass swards and decreased by almost 50% in cut grass-clover swards, deposition of excreta must be expected to be proportionally higher in ryegrass swards (assuming some similarity between cut and grazed grass production). This was confirmed by higher and considerably more variable nitrate concentrations in drainage extracted by the ceramic suction cups in old grazed ryegrass swards compared with grass-clover, probably due to urination by the grazing cattle. These observations suggest that the high nitrate leaching loss in ryegrass was not directly due to the fertiliser input, but rather an indirect effect of fertilisation on grass production leading to increased grazing and thus increased recycling of N in dung and urine to the sward.

Nitrate leaching and N2-fixation in grasslands of different composition, age and management

A grazing experiment was carried out to study the concentration of phyto-oestrogens in herbage for cattle and in milk during two periods (May and June). Forty-eight Danish Holstein cows were divided into four groups with four treatment diets; white clover, red clover, lucerne and chicory-rich pastures. Each experimental period lasted 15 days. Herbage samples from the first day and individual milk samples from the last day of the experimental period were analysed for phyto-oestrogens using LC-MS technique. The total concentration of phyto-oestrogens was 21 399 mg/kg dry matter (DM) for red clover and 238 to 466 mg/kg DM for the other three herbages mainly due to a much higher concentration of biochanin A, formononetin and glycitein in red clover. In the milk, the total concentration of phyto-oestrogens was 253 to 397 μg/l for red clover milk and 56 to 91 μg/l in the milk from the other three treatments. This was especially due to a higher concentration of equol, daidzein and formononetin in the red clover milk. The concentration of biochanin A was significantly higher in milk from the red clover treatment in May while no differences were observed in June. Enterodiol was similar across treatments while the concentration of enterolactone was significantly lower for red clover milk compared with the other treatments. Of the tested pastures, red clover appears to have the highest concentration and to be the best source of phyto-oestrogens, especially equol, in bovine milk.

https://findresearcher.sdu.dk:8443/ws/files/99345640/Frette_2009_Animal.pdf

Karen Søegaard

Papers

Nitrogen transfer from forage legumes to nine neighbouring plants in a multi-species grassland

N2-fixation and residual N effect of four legume species and four companion grass species

Forage herbs improve mineral composition of grassland herbage

Nitrate leaching and N2-fixation in grasslands of different composition, age and management

Phyto-oestrogens in herbage and milk from cows grazing white clover, red clover, lucerne or chicory-rich pastures