Legume Futures Report 3.8/6.6
Policy implications of the environmental and resource effects of
legume cropping
Prepared by:
Michael Williams, Jane Stout and Susannah Cass, Trinity College Dublin,
Ireland
Jenny Fischer and Hewart Böhm, Thünen-Institute for Organic Farming,
Westerau, Germany.
Donal Murphy-Bokern, Germany
Tom Kuhlman, Wageningen University, The Netherlands
Fred L. Stoddard and Kristina Lindström, University of Helsinki, Finland
Christine Watson, Valentini Papa and Kairsty Topp, Scotland's Rural
College, United Kingdom
Moritz Reckling, Sara Preißel, Andrea Bues and Peter Zander, Leibniz
Centre for Agricultural Landscape Research, Germany
Marie Trydeman Knudsen, Jørgen E. Olesen, John E. Hermansen and Kirsten
Schelde, Department of Agroecology, Aarhus University, Denmark
25 February 2014
Legume-supported cropping systems for Europe (Legume Futures)
is a collaborative research project funded from the European Union’s Seventh Programme
for research, technological development and demonstration under grant number 245216
www.legumefutures.de
Legume-supported cropping systems for Europe
Legume Futures
Legume-supported cropping systems for Europe (Legume Futures) is an international
research project funded from the European Union’s Seventh Programme for research,
technological development and demonstration under grant agreement number
245216. The Legume Futures research consortium comprises 20 partners in 13
countries.
Disclaimer
The information presented here has been thoroughly researched and is believed to be
accurate and correct. However, the authors cannot be held legally responsible for any
errors. There are no warranties, expressed or implied, made with respect to the
information provided. The authors will not be liable for any direct, indirect, special,
incidental or consequential damages arising out of the use or inability to use the content
of this publication.
Copyright
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prohibited.
Citation
Please cite this report as follows:
Topp, K., Watson, C., Papa, V. Williams, M., Stout, J., Cass, S., Fischer, J., Böhm, H.,
Murphy-Bokern, D., Kuhlman, T., Stoddard, F.L. Lindström, K., Reckling, M., Preißel, S.,
Bues, B., Zander, P., Knudsen, M.T., Olesen, J.E., Hermansen, J.E.M., Schelde, K.
2014. Policy implications of the environmental and resource effects of legume cropping.
Legume Futures Report 3.8/6.6. Available from www.legumefutures.de
Legume Futures Report 3.8/6.6: Policy implications of the environmental and resource effects of legume
cropping
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Legume-supported cropping systems for Europe
CONTENTS
FOREWORD............................................................................................................................... 4
SUMMARY ................................................................................................................................. 5
INTRODUCTION ........................................................................................................................ 6
RESOURCE AND ENVIRONMENTAL EFFECTS ....................................................................... 7
Resource effects ..................................................................................................................... 7
Reduced use of synthetic nitrogen fertiliser ............................................................... 7
Phosphorus ............................................................................................................... 9
Farm-level environmental effects ........................................................................................... 10
Nitrous oxide emissions .......................................................................................... 10
Emission factors for nitrous oxide flux ..................................................................... 14
Leaching of nitrogen ................................................................................................ 14
Impacts of legume cropping on above and below ground biodiversity .................... 17
Assessments of crop products and cropping systems ............................................. 17
Assessments of protein crop-based animal production ........................................... 20
POLICY IMPLICATIONS ........................................................................................................... 24
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FOREWORD
Legume Futures, "Legume-supported crop rotations for Europe", is an international
research project funded under the European FP7 programme. It has 20 partners in 13
countries. The project aims to develop and assess legume-supported cropping systems
that improve the economic and environmental performance of farming in Europe.
Legume Futures produces information relevant to both the development of legumesupported cropping by farmers and other actors in the agricultural sector and to the
policy community. This report is aimed at the policy community in particular. The
purpose is to provide a synthesis of information about the environmental impact of
legume crops, including both background literature information and results of research in
Legume Futures. From our assessments of the economic performance of legume crops,
we know the policy community will remain key to the development of legume cropping in
Europe for the foreseeable future.
Kairsty Topp
SRUC Edinburgh, UK
27 February 2014
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Legume-supported cropping systems for Europe
SUMMARY
Compared with other major agricultural regions of the world, Europe is characterised by
a lower share of legumes in cropping systems. This is because land is preferentially
allocated to cereals or to oilseeds in most of Europe’s cropping regions. Cereals grow
particularly well in Europe generally. The demand for plant protein which current
cropping cannot fully meet comes from a livestock sector scaled to meet the EU’s high
demand for meat. Our assessment of the environmental impact of increasing legume
cropping concludes that increasing the production of protein crops would be an
important contribution to the sustainable development of European agricultural and food
systems. The direct farm and regional level environmental benefits combined with the
indirect benefits arising from the better balance of EU agriculture and trade justify public
intervention. We recommend that policy makers focus on the public benefits of
increased legume cropping in the context of a wider re-balancing of European
agricultural and food systems. This requires an integrated approach to policy
development, which sees legumes expansion as a component of a wider effort to
develop a more sustainable agriculture and food system.
The reform of the common agricultural policy that is now being implemented includes
two measures specific to protein crops: the consideration of nitrogen-fixing crops as part
of the Ecological Focus Areas and limited provision for national coupled support for
protein crops. In addition, protein crops are the subject of the first focus group advising
the EU European Innovation Partnership on agriculture and food.
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INTRODUCTION
Legumes play a vital role in European agriculture, but most of the legumes used are
grown outside Europe. The EU imports 70% of its requirement for high-protein crop raw
material, mostly as soya from South America. This accounted for about 14% of the
world-wide production of soya bean from about 15 M ha of arable land outside the EU in
2011. Over the 50 year period 1961-2011, the production of beef, pig and poultry meat
in the EU-27 has increased from 17 to 43 million t, with a particularly large increase in
pig and poultry meat (See Legume Futures Report 5.3). While demand for livestock
feed increased, our production of protein crops has decreased (Figure 1). Protein crops
are now grown on only 1.8% of arable land in the EU, compared with 4.7% in 1961. In
contrast, they are grown on about 8% of arable land in Australia and Canada. The direct
human consumption of pulses has also declined. It is estimated that only 11-15% of pea
and 9-14% of faba bean grown are now used for human consumption. A major
underlying driver behind the reduction in the proportion of arable land used for protein
crops is the increased comparative advantage in the production of starch-rich cereals.
Area (million ha)
1974: price
support for
soya bean
3.0
2.5
1992:
MacSharry
reform
1978: price
support for
pea, faba
bean, lupins
2005 - 2006:
introduction of
Single Payment
Scheme
1989: area
payment for
chickpea,
lentil, vetches
2.0
1.5
1.0
0.5
0.0
1960
1965
1970
1975
1980
1985
1990
1995
2000
2005
2010
Common bean
Faba bean and other legumes
Chickpea, lentil & vetches
Pea
Lupins
Soya bean
Figure 1. Production areas of different protein crops in the EU-27 in relation to policy
events (1961-2011). Data source: FAOSTAT (2013)
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Legume-supported cropping systems for Europe
RESOURCE AND ENVIRONMENTAL EFFECTS
Particularly in developing public policy, it is important to distinguish between the
resource and environmental effects of legume cropping. Biological nitrogen fixation,
which is a distinguishing feature of cultivated legumes, has both resource and
environmental effects.
Resource effects
Reduced use of synthetic nitrogen fertiliser
Protein crops require almost no N fertiliser to express their yield potential while the
cereal crops they normally replace typically receive 100-200 kg N/ha. As a result, the
production of protein crops directly reduces nitrogen fertiliser use. Furthermore, the large
quantity of nitrogen in the residues of legumes allows the saving of considerable
amounts of nitrogen fertiliser in the following crops (Fig. 2).
Figure 2:
The on-farm nitrogen cycle, showing the effect of legume pre-crops
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The residual N combined with other precrop effects such as the reduction in root
diseases that reduce nitrogen uptake can be expressed as a fertiliser nitrogen
equivalent. This is reported to be as much as 120 kg N/ha (Chalk 1998; Köpke and
Nemecek 2010). However, the public benefits of this depends on how well farmers take
it into account when fertilising the following crops. A survey of agronomic experts for the
Legume Futures project reported that the savings made in practice are significantly less
(Table 1). It appears that many farmers fertilise the crop after legumes as they would
after other crops and treat the legume-derived N as a bonus that supports the higher
yield and protein content normally achieved in these situations. This means the full
potential environmental and resource benefits of protein crops are often not realised.
Forage legumes fix significantly more nitrogen than grain legumes due to their high
biomass production and longer growth period.
Studies using nitrogen labelled with non-radioactive isotopes (15N labelling methods)
show that only a relatively small proportion of nitrogen residue from protein crops is used
by the next crop through direct take-up (Fig. 2). As much as 75% of the total residue
enters the soil reserve, providing a resource for the longer-term supply of other crops.
Thus there is a resource impact for the farm and an environmental impact due to
reduction in fertiliser manufacture.
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Legume-supported cropping systems for Europe
Table 1: Fertilisation practices for major protein crops and winter wheat in five case
study regions across Europe
Crop2
Yield
(t/ha)
Regional average mineral
fertiliser applied (kg/ha)
N
P
K
Experts view of
mineral N fertiliser
saved in succeeding
wheat (kg N/ha)
Faba bean
1.6-5
0
15-20
25-45
0-20
Pea
1.2-4
0
15-20
25-40
0-20
Lupins
2.5-3
0-30
15-35
30-35
0-20
Forage legumes, dry matter
6-15
0-65
0-15
0
0-20
Winter wheat
3.2-8
135-200
25-30
20-60
1
2
0
Location and soil type: Scotland (Eastern, grade 3), Italy (Calabria, loam), Sweden (Västra
Götalands, silty clay loam), Germany (Brandenburg, sandy clay loam) and Romania (Sud-Muntenia,
Chernozem)
IT (faba bean, pea and lupins), SE (faba bean and pea), SC (faba bean and pea), RO (pea), DE (faba
bean, pea and lupins)
Phosphorus
There is considerable evidence also that legumes improve the efficiency of soil
phosphorus utilisation through mycorrhizal associations with the roots of legume species
(Ren et al. 2013). Legume roots are able to alter the pH of the soil and influence
phosphorus availability accordingly (Betencourt et al. 2012; Li et al. 2013). Experiments
with faba beans have shown that the acidity produced by the roots of these plants is
more effective at solubilising soil phosphorus than that from other legume species.
Legume-supported rotations (including intercrops) are of particular value in soils with
lower phosphorus content or in circumstances where phosphorus is applied in insoluble
forms. This is particularly relevant in organic farming where regulations preclude the
use of soluble phosphorus fertilisers, preferring instead to use composts or manure or
other forms of phosphorus input such as rock phosphate.
However extreme
phosphorus deficiency (often encountered in low pH soils) can result in reduced growth
of legumes in rotation as this becomes the next most limiting nutrient after nitrogen.
Other resource advantages to legume cropping would be increasing the organic matter
content and water-absorbing capacity of the soil, thus increasing the yield of following
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Legume-supported cropping systems for Europe
crops, reducing erosion, and increasing the soil carbon content (Jensen et al., 2012).
Protein crops break the cycles of soil-borne diseases of cereals so less pesticide is
needed in the following crop.
Farm-level environmental effects
Nitrous oxide emissions
The evidence available indicates that nitrous oxide emissions from legume crops in
general are low compared with high N input agriculture (Table 2) with annual emissions
from legume crops being towards the lower end still (Fig. 3). Exceptions to this are the
use of legume crops as green manures in organic farming where nitrous oxide
emissions may approach those of fertilised crops. The problem here being the high N
content and low C:N ratio of legume plant residues which result in more rapid
mineralisation, an excess of N with respect to microbial growth and increased substrate
for the combined processes of nitrification and denitrification. In general, greater N2O
emissions are measured after incorporation of high N plant residues. One strategy that
may prolong mineralisation of legume residues through the season and reduce the burst
in N2O flux on incorporation would be to manipulate the overall C:N ratio of the plant
material applied. This may be achieved by mixing high C cereal residues with high N
legume residues to allow for some measure of N immobilisation (Vinten et al., 1998;
Myers et al., 1994; Schwendener et al., 2005; Kaewpradit et al., 2008; Frimpong et al.,
2011).
Table 2: N2O fluxes from different soil use and management (from Muňoz et al., 2010)
Cropping
Continuous
rotation crops
Range N2O flux
(kg N2O-N ha-1 yr-1)
and 0 – 44
Country
Brazil, Canada, Denmark,
New Zealand
Leguminous crop
0.3 – 4.7
Canada
Rice
0 – 36
Australia, USA, Japan, China, Philipines,
Indonesia, Taiwan, India
Shrub land/ Natural 0 – 21
Landscape
New Zealand, Finland
Pastures:
animal 0 – 156
waste applied
Canada, New Zealand, England, The
Netherlands, Japan, Canada, Denmark, USA
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Choice of grain legume species and cultivars may influence annual emissions of nitrous
oxide. From preliminary studies it would seem that careful selection of cultivar and
rhizobium inoculants may achieve reductions in nitrous oxide flux. Growing plants may
influence the N2O flux to the atmosphere in a variety of ways from providing
carbohydrate substrate directly through root exudates and root turnover (Qian et al.,
1997; Mounier et al., 2004; Henry et al., 2008; Broeckling et al., 2008; Philippot et al.,
2009), through anatomy of the stem and leaf (Baruah et al., 2012) and in the case of
legumes, through differences in nodule and rhizobial activity (Garcίa-Plazaola et al.,
1996; Pappa et al., 2011). Data from bean and pea cultivar trials show marked species
and cultivar differences in emissions of nitrous oxide (Figures 4 and 5).
lentil (Romania)
lupin (Romania)
pea (Scotland)
mungo bean (Romania)
common bean (Greece)
faba bean (Italy)
faba bean (Scotland)
soybean (Romania)
0
1
2
3
4
Annual emissions of N2O (kg N2O-N ha-1 y -1)
Figure 3: Annual emission of nitrous oxide from grain legumes (data from Legume
Futures)
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Legume-supported cropping systems for Europe
Figure 4: N content of legume and non-legume plant residues (after Jensen et al., 2012).
Brown bars indicate residues with C:N ratio of less than 26:1.
Annual variation in emissions of nitrous oxide must be taken into consideration when
evaluating choice of crop or cultivar. Inter-annual changes in soil condition, namely
rainfall in the case of data shown in Figures 5 and 6, alter the aerobic nature of the soil
and hence nitrous oxide flux (Davidson, 1991; Davidson et al., 2000; Smith et al., 2003),
the capacity of the soil to produce nitrous oxide being determined by substrate supply,
organic carbon status and percentage clay fraction of the soil (Beauchamp et al., 1980;
Maag & Vinther, 1996; Smith et al., 1998).
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Annual emissions of N2O
(kg N2O-N ha-1 yr-1)
3
Faba bean
2008 - 899mm rainfall
2,5
2009 - 1160mm rainfall
2
1,5
1
0,5
0
A
B
C
D
E
Figure 5: Nitrous oxide emissions (mean ± standard error) for faba bean cultivars from
SRUC Craibstone Estate, Scotland. Data provided by John Baddeley for Legume
Futures
8
Annual emissions of N2O
(kg N2O-N ha-1 yr-1)
7
Pea
2008 - 899mm rainfall
2009 - 1160mm rainfall
6
5
4
3
2
1
0
A
B
C
D
E
F
G
Figure 6: Nitrous oxide emissions (mean ± standard error) for pea cultivars from SRUC
Craibstone Estate, Scotland. Data provided by John Baddeley for Legume Futures.
Different legume based cropping systems can influence N2O emissions per unit of grain
production (emission intensity: g N2O-N per tonne product) in both the legume cropping
year and the following year. Data from field studies across Europe conducted in the
Legume Futures project highlight differences between crop and geographic region in
terms of nitrous oxide emission intensity. In Romania, emission intensity values for
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Legume-supported cropping systems for Europe
winter peas and soybeans were 120 g N2O-N t-1 grain yield for the year of legume
cropping, ten percent less than the emission intensity for unfertilised winter wheat. In
Italy legume monocrops (pea and faba bean) had significantly higher emission
intensities than cereal monocrops, but growing both legumes and cereals together
(intercropping) reduced the nitrous oxide emission intensity values by 50 to 75%. In
Scotland, all grain legumes tested having values significantly less than those for
unfertilised winter wheat (298 g N2O-N t-1 grain yield).
Emission factors for nitrous oxide flux
A number of reviews highlight that where N is provided to the soil by biological nitrogen
fixation (BNF) the associated N2O emissions are significantly lower and in many
circumstances no different to unfertilised control environments (Bouwman et al., 2002;
Rochette & Janzen, 2005). This has led to revisions of the reporting guidelines prepared
by the IPCC with the recommendation that no N2O emissions would be associated with
inputs of N by BNF (IPCC, 2006). The evidence for this revision remains somewhat
circumstantial, and furthermore the extent to which decomposition of residues from
legume plants contributes to emissions is highly uncertain (Baggs et al., 2000).
Field data from the Legume Futures project has allowed an estimate of the nitrous oxide
emission factor for biological nitrogen fixation for grain legumes of 0.11 ± 0.05%, so low
as to support the present reporting procedure (Figure 7). In terms of reducing
greenhouse gas emissions from agriculture in a way that is registered in national
emission inventories, there is a clear advantage from increasing the acreage of legume
crops grown.
Leaching of nitrogen
One negative aspect of protein crops is the potential for increased leaching of N.
Agriculture still remains a major source of water-related problems in Europe caused in
the main by the use of nitrates in mineral fertilisers and organic manures. Here the
organic nitrogen compounds within the soil are mineralized by microorganism and
converted to plant available inorganic nitrogen compounds. If soils contain excessive
amounts of nitrogen, as a result of high fertilization, biological nitrogen fixation from
legumes and/or mineralisation rates that exceed uptake by the plants, there is a high risk
of leaching the water soluble nitrate (NO3-) whereas ammonium (NH4+) and organic
nitrogen compounds are usually prevented from leaching as they are retained by the soil.
Many studies show that the effects of legume crops on eutrophication, i.e. the abundant
accumulation of nutrients, are the result of two counteracting processes: nitrate
emissions to water from the legume crop itself are low, which leads to very favourable
effects of pea and faba bean compared to other domestic crops, but emissions in the
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Legume-supported cropping systems for Europe
subsequent crop are frequently reported to be higher due to losses from the N-rich
legume residues, combined with longer uncropped periods before or after legume
cultivation due to their shorter growth periods in comparison with autumn-sown crops.
Therefore, the outcome of the assessments of legume crops range from very positive to
very negative, and the comparisons of crop rotations reveal non-significant to somewhat
negative effects of including protein crops (Table 3).
The effects of including legume crops in crop rotations on ecotoxicity, i.e. the negative
impacts of biocide applications, could not be determined due to differences between
assessment methods (Nemecek and Baumgartner 2006). The study assumed that the
diversification of the rotations, leading to lower shares of cereals (including maize),
would reduce disease pressure and pesticide applications in cereals, but the application
of insecticides in legumes off-set this benefit.
EFall
EFfaba bean
EFcommon bean
EFwinter bean
EFpea
1.
0
0.
5
0.
0
-0
.5
EFGalega
Emission Factor for BNF (%)
Figure 7: Calculated emission factors (EF) for biological nitrogen fixation (BNF) from
legume crops. Overall EF for grain legumes is 0.11 ± 0.05%.
As reported by Jensen et al., (2004) the soil nitrate content is often higher after grain
legumes than after cereals, which is presumably due to the root density and distribution
as well as the lower C:N ratios of grain legume residues (~15-25) in comparison to
cereals (~40-50). The risk of postharvest losses after the cultivation of legumes is
increased if the available nitrogen from efficient BNF is not taken up by the succeeding
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Legume-supported cropping systems for Europe
crop before the seepage period starts. Beaudoin et al., (2005) observed the highest
rates of nitrate leaching in crop rotations including pea for Northern France due to the
higher N content of plant biomass and lower N uptake rates from the soil, whilst one
recent study on the use of legumes as cover crops in Capsicum production showed both
high N leaching and a linear correlation between the N accumulated in the legume
biomass and the total amount of nitrate leached (Campiglia et al., 2011). Targeting the
reduction of mineral N accumulation in soil, synchronising N inputs with crop growth and
crop N uptake and avoiding the build up of excess N in soils would contribute towards
decreased leaching and one possible way to achieve this would be through intercropping of legumes with cereals.
Figure 9: Cumulative NO3-N load of faba bean in sole-cropping and intercropping with
oat, during the autumn-winter seepage period (7 November 11 to 21 March 12). Data
from Legume Futures project provided by Jenny Fischer and Herwart Böhm.
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Impacts of legume cropping on above and below ground biodiversity
Environmental benefits of legume cropping are best described in terms of N use and
efficiency than biodiversity. A review of biodiversity and ecosystem services in legumesupported cropping funded through Legumes Futures (Cass et al., 2014), highlights a
lack of consistency in the literature on the effect of legume crops on vegetation diversity
or above and below ground invertebrate diversity. A clear divide exists in data from
studies investigating the use of legumes to reduce populations of certain organisms and
those studies investigating legume-treatments for promoting associated biodiversity.
Management factors, not crop are the main influences on biodiversity although legume
biomass tends to increase the potential carrying capacity for associated biodiversity.
Legume-supported cropping can both promote and reduce biodiversity within systems
but appears to have a generally positive impact at the widest scales.
European and global environmental impacts
The environmental impacts of protein crops at the crop level have the potential to reduce
the overall environmental impacts of agricultural production more widely and improve the
environmental profile of food products. Life Cycle Assessment (LCA) is a method that
considers the environmental effect of processes within a production system and
provides a means for comparing the environmental impacts and resource use of
commodities, products and processes. LCA has particular strengths in assessing
impacts at the continental and global levels as it rigorously quantifies the GHG
emissions and other environmental consequences (such as eutrophication and
acidification) associated with a product throughout its life-cycle, from ‘cradle to grave’
(Brentrup 2004). Results are expressed in relation to impact factors, including fossil
energy use, GHG emission, eutrophication, acidification, ecotoxicity, and land use. It is
now widely used to inform policy development. The LCAs reviewed here assessed the
environmental impact of protein crops in relation to the land used and the commodity
output.
Assessments of crop products and cropping systems
Several studies have compared the life cycles of domestically produced pea and faba
bean with imported soya bean and with other European crops (averages of rapeseed,
cereals, potatoes; Cederberg and Flysiö 2004, Eriksson et al. 2005, Van der Werf et al.
2005, Nemecek et al. 2005). In order to take into account the effects of growing protein
crops on the cropping system, Nemecek and Baumgartner (2006) compared crop
rotations with and without protein crops (mostly pea) at four sites. These LCAs also
consider the legume’s effect on subsequent crops and on the choice of crops that are
replaced when protein crop production is increased.
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Legume-supported cropping systems for Europe
It should be noted that these studies over-estimate GHG emissions from legumes due to
applying pre-2006 methodologies that assumed direct emissions of nitrous oxide during
legume growth. In most cases, European-grown protein crops (mostly pea) are
associated with significantly reduced fossil energy use, GHG emissions, ozone
formation and acidification compared to imported soya bean and other crops on a per
unit product basis (Table 3). Reductions in nitrogen fertiliser use were the main reason
for the reduction in energy inputs and associated emissions. Nevertheless, emission
intensities associated with grain legumes are dependent on the management of that
crop and the assumptions regarding the pre-crop effect on the following crop in the
rotation (Figure 10). In addition, the results for cropping systems were greatly affected
by the assumptions about the crop being replaced by the protein crop. For example, the
displacement of grain maize with the avoidance of the large amounts of energy used in
drying the maize grain dominated the environmental benefits of the switch to the protein
crop in a Swiss study. In a case in Spain, the protein crop replaced an unfertilised crop
(sunflower), so no fertiliser savings occurred, and small or even negative environmental
effects resulted from the inclusion of protein crops in the cropping system.
PEA
Increased cereal yields, precrop effect
SC
-20 -36 15
97
47
Avoided fertilizer production, precrop effect
Input production
SE
-26
-48
11
100
N2O emissions
63
Energy consumption
RO
IT
-26
-66
14
-121
-26
DE
-200
-48
-100
86
63
48
-48
13
0
203
124
158
66
100
200
300
400
Greenhouse gas emissions (kg CO2 eq. per t grain DM)
Figure 10. The contributions to the greenhouse gas emission per t harvested grain DM
for pea grown at five different regions in Europe: Scotland (SC), Sweden (SE), Italy (IT)
and Germany (DE) . Sourced from Knudsen et al. (2014).
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Legume-supported cropping systems for Europe
However, the environmental benefits of protein crops are constrained by low yields
which limits the environmental benefits on a per unit product basis (see also the
contrasting impacts on landuse, Tables 2 and 3). Low yields led to non-significant effects
on energy use and negative effects on GHG emissions and ozone formation per kg
product in a Swiss case (Nemecek et al. 2005). In the comparisons of crop rotations,
such yield differences are not factored into the assessment but reduced environmental
benefits due to low yields have also been noted (Nemecek and Baumgartner 2006,
Baumgartner et al. 2008).
Table 3: Comparison of the results of LCA studies of protein crop products compared
to other crops (%)
Region
% change in environmental impact
Energy
demand
GHG
emission
Ozone
Eutrophication
Acidification
Ecotoxicity
Landuse
Comparison of European-grown pea to other crops6 (per kg produce)
Sweden1
-27
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
Sweden2
-35
n.s.
n.s.
75
-12
n.s.
n.s.
Switzerland4
n.s.
11
25
-52
-48
n.s.
n.s.
Comparison of European-grown pea to imported soya meal/cake (per kg produce)
Sweden1
-70
n.s.
n.s.
n.s.
n.s.
n.s.
n.s.
Sweden2
-78
-57
n.s.
-50
-87
n.s.
32
France3
-64
-44
n.s.
-17
-67
n.s.
-58
Comparison of crop rotations with protein crops to those without (per ha land)
Germany5
-14
-12
-10
n.s.
-17
(-)7
n.s.
France5
-11
-8
-6
n.s.
-18
(-)
n.s.
Switzerland5
-31
-9
-15
10
-14
(+)
n.s.
Spain5
n.s.
13
6
15
n.s.
n.s.
n.s.
Colour coding4
very
favourable
favourable
n.s.,
not unfavourable
significant
Very
unfavourable
Source: Calculations based on data from: 1Cederberg and Flysiö (2004), 2Eriksson et al. (2005), 3Van der
Werf et al. (2005), 4Nemecek et al. (2005), 5Nemecek and Baumgartner (2006), 6other crops: average of
wheat, barley, rapeseed, 7conflicting results of different assessment methods.
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Legume-supported cropping systems for Europe
Assessments of protein crop-based animal production
As the vast majority of protein crop commodity is used in animal feeds and provides an
alternative protein source to imported soya bean, the question arises as to how the
increased use of European-grown protein crops affect the environmental performance
over the life cycle of animal products (meat, milk, eggs) based on such feeds.
The role of feed crop production on the life-cycle effects of animal products is high. In
the life-cycle of livestock commodity products (carcass meat, milk etc.), feed production
accounts for:
 50-75% of energy consumption,
 47-88% of greenhouse gas emissions,
 50-98% of eutrophication,
 28-98% of acidification,
 >90% of ecotoxicity, and
 >96% of land use
(Blonk et al. 1997, Eriksson et al. 2005, Van der Werf et al. 2005, Ellingsen and
Aanodsen 2006, Nemecek and Baumgartner 2006, Katajajuuri 2007, Baumgartner et al.
2008).
The comparison of animal products based on different feeding regimes is not simply a
function of the environmental benefits of legumes, but also depends on the different
feeding values of the components and associated changes in feed composition required
to maintain a high animal performance. In many studies, inclusion of pea in feed
formulas partially replaced both soya and cereals, since pea contain large amounts of
starch as well as protein. There are nutritional constraints on the extent to which soya
protein can be replaced by other protein crop sources in conventional commercial
farming systems.1 In addition, changes in animal productivity and excretions of nitrogen
compounds are considered.
Besides crop production, the transport-related environmental impacts can in some cases
be significantly reduced by replacing soya bean meal with European grain legumes
1
Pea and faba bean have lower protein concentrations and different protein qualities than soya, so their
inclusion at 10-24% of feed is required to replace soya that is included at 8-13% of feed (Cederberg and
Flysiö 2004, Eriksson et al. 2005, Nemecek and Baumgartner 2006, Baumgartner et al. 2008, Köpke
and Nemecek 2010, Houdijk et al. 2013).
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Legume-supported cropping systems for Europe
(Baumgartner et al. 2008), but often the difference between overseas imports by sea
and EU inland transport by canal, rail and road to feed compounding industries is
smaller than one might expect. Differences in transport have generally minor effects on
the overall environmental impacts of end products.2
In most studies, the fossil energy use required for the production of a unit of animal
product and the associated GHG emissions decreased where European-grown protein
crops are used (Table 3). The reductions were caused by reductions in transport and
partial replacement of cereals in feeds (see above). Nevertheless, Topp et al. (2012)
found that emissions per unit of meat product were similar for soya and the Europeangrown grain protein based diets. However, incorporating land-use change (deforestation
and destruction of grasslands in South America) into the LCA resulted in the Europeangrown protein diets having an advantage over the soya-based diets in terms of GHGs
(Topp et al. 2012). In addition, taking into account the fact the more palm oil may be
produced to compensate for the lower availability soya bean oil, and the fact that the
crop replaced by the grain legume will be grown outside Europe still results in a net
benefit in greenhouse gas emissions (Table 4).
2
Transport contributes 4-27% of energy demand, 2-15% of GHG emissions and around 18% of
acidification in the studies listed hereafter.
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Legume-supported cropping systems for Europe
Table 4: Comparison of results of LCA studies of animal products produced using
different feed compositions (%)
Region
% change in environmental impact
Energy
demand
GHG
emission
Ozone
Eutrophication
Acidification
Ecotoxicity
Landuse
-36
n.s.
Comparison of soya-based to domestic legume-based feed (per kg end-product)
Sweden, pork1
-16
-13
-31
-40
Sweden, pork2
-19
-10
n.s.
n.s.
Germany,
Spain,
pork3
pork3
France, chicken
meat3
France, eggs3
24
n.s.
-5
n.s.
n.s.
n.s.
(+)5
-6
n.s.
n.s.
17
n.s.
(+)
32
-6
-10
n.s.
n.s.
n.s.
(+)
n.s.
-4
-10
-5
n.s.
n.s.
+
n.s.
milk3
n.s.
UK,
-9
n.s.
n.s.
n.s.
n.s.
n.s.
Comparison of soya-based to farm-produced legume-based feed (per kg end-product)
n.s.
Germany, pork3
n.s.
Colour coding4
-19
very
favourable
-16
-25
favourable
-11
-10
n.s.
n.s.,
not unfavourable
significant
Very
unfavourable
Source: Calculations based on data from: 1Cederberg and Flysiö (2004), 2Eriksson et
al. (2005), 3Baumgartner et al. (2008), 4Nemecek and Baumgartner (2006)5 conflicting
results of different assessment methods.
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Legume-supported cropping systems for Europe
Table 5. The overall climate impact when replacing one hectare of wheat in Europe with
pea production, while taking the impact of a reduced soybean import to Europe and an
increased wheat production outside Europe into account.
Kg CO2 emissions per ha of pea cultivated in Europe
EMISSIONS
1 hectare of pea production in Europe
296
Production of wheat outside Europe
2524
Production of palm oil (to account for less soybean oil produced)
711
TOTAL emissions
3531
AVOIDED EMISSIONS
1 hectare of wheat production in Europe
-2343
Soybean production
-329
cake3
-230
Transport of soybean cake to Europe
-175
Extra carbohydrates in peas compared to cake of soybean, avoided cereal production
-733
Soybean, processing to oil and
TOTAL avoided emissions
OVERALL climate impact
-3810
-279
Feeding European-grown legume crops has shown little effect on ozone formation,
eutrophication, acidification, ecotoxicity and land-use (Table 5). Ozone formation and
acidification were positively affected in one case. Eutrophication was in one case
negatively and in one case positively affected, and ecotoxicity effects depended on the
assessment method. The amount of land required for feed production was very
negatively affected in two case studies, but not significantly so in all others.
On-farm feeding of home-grown legumes increases benefits further, as shown in one
case study that considered on-farm production (Table 6, Baumgartner 2008). In this
case study, greatly reduced transport led to lower energy demand, and greater
advantages in terms of GHGs, ozone formation and acidification (Baumgartner et al.
2008). However, an on-farm feed producer may not achieve the efficiency of animal feed
manufacturers, leading to higher feed costs and lower animal performance from farmproduced feeds.
3
Dalgaard R, Schmidt J, Halberg N, Christensen P, Thrane M, Pengue W (2008) LCA of soybean meal.
International Journal of Life Cycle Assessment 13:240-254.
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Legume-supported cropping systems for Europe
It is concluded that a greater inclusion of European protein crops in feed improves the
environmental performance of animal products, especially with respect to fossil energy
use and GHG emissions, as well as other impact categories in some cases.
Improvement of yields through research and agronomic innovations could greatly
increase these environmental benefits. However, the European production of protein
crops, even if it were significantly increased, can only satisfy a small share of the
European feed demand at current levels of crop yield, animal production and
consumption.4
POLICY IMPLICATIONS
Protein crops have multiple positive environmental and resource-conserving effects
operating at field, farm, regional and global levels. These effects point to the need to
recognise the potential of complementary policy measures and to foster efforts to
enhance this complementarity. Such an integrated policy approach can be particularly
robust if it focuses on the positive outcomes that protein crops can bring about for
society. To make them complementary to one another, measures should be rooted in an
understanding of the agroecological processes governing the benefits.
With the current low use of protein crops, the promotion of legumes through greening
measures can be justified from a practical policy viewpoint. Combined with investment in
research and development, this could stimulate private-sector investment in crop
improvement and technical progress. This private investment in technical change is
important because the current status of protein crops in Europe is determined largely by
the yield advantage of carbohydrate-rich cereals. This is a consequence of climate over
much of Europe which, despite its diversity, tends to favour high yields of cereals. This
means that in the long term, a closing of the yield gap between protein crops and
cereals, particularly in terms of protein yield, is an important strategic goal. There is also
a need to improve the ability to capture for farmers the on-farm economic benefits of
more diverse rotations that include legumes.
The Member States of the European Union are now at various stages in deciding how to
respond at national level to the CAP reform decisions made so far. The most relevant
measure is the consideration of nitrogen-fixing crops as contributing to the EFA
4
When we consider the total compound feed production in the EU (150 million tonnes, EUFETEC 2010)
and the average pea yield, an EU-wide replacement of only 1% of the average compound feed by
European fodder pea would require an increase in production areas to their historic peak in the late
1980s.
Legume Futures Report 3.8/6.6: Policy implications of the environmental and resource effects of legume
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Legume-supported cropping systems for Europe
requirement. Any ‘watering-down’ of this measure, either direct or indirect, will reduce
the impact of reform on legume cropping.
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