As costs for mineral fertilizers rise, legume-based leys are recognised as a potential alternative nitrogen source for crops. Here we demonstrate that including species-rich legume-based leys in the rotation helps to maximize synergies between agricultural productivity and other ecosystem services. By using functionally diverse plant species mixtures these services can be optimised and fine-tuned to regional and farm-specific needs. Field experiments run over three years at multiple locations showed that the stability of ley performance was greater in multi-species mixtures than in legume monocultures. In addition, mixing different legume species in the ley helps to suppress both early and late weeds. Further, combining complementary phenologies of different legume species extended forage availability for key pollinator species. Finally, widening the range of legume species increases opportunities to build short term leys into rotations on conventional farms via cover cropping or undersowing

Baddeley, J. A.

Brown, RJ

Collins, R

Crowley, Oliver

Cuttle, Steve

Döring, Thomas F.

Jones, H E

McCalman, Heather

Pearce, Bruce

Roderick, Stephen

Stobart, Ron

Storkey, Jonathan

Watson, Christine

Wolfe, Martin

English

Organic Eprints

Agriculture and the Environment IX, Valuing Ecosystems: Policy, Economic and Management Interactions (2012)  150 LEGUME  BASED  PLANT  MIXTURES  FOR  DELIVERY  OF  MULTIPLE ECOSYSTEM SERVICES: AN OVERVIEW OF BENEFITS  *TF  Döring1,  J  Storkey2,  JA  Baddeley3,  O  Crowley1,  SA  Howlett1,  H  McCalman4,            H Pearce1, S Roderick5 and HE Jones6  1The  Organic  Research  Centre,  Hamstead  Marshall,  RG20  0HR,  UK,  E-mail: thomas.d@organicresearchcentre.com; 2Rothamsted  Research,  Harpenden,  AL5  2JQ,  UK; 3SAC, Craibstone Estate, Aberdeen, AB21 9YA, UK; 4Institute of Biological, Environmental and Rural Sciences, Aberystwyth University, Aberystwyth, SY23 3EB, UK; 5Duchy College, Camborne, Cornwall, TR14 OAB, UK; 6University of Reading, Earley Gate, PO Box  237, Reading, RG6 6AR, UK  SUMMARY  As costs for mineral fertilizers rise, legume-based leys are recognised as a potential alternative nitrogen source for crops. Here we demonstrate that including species-rich legume-based leys in  the  rotation  helps  to  maximize  synergies  between  agricultural  productivity  and  other ecosystem services. By using functionally diverse plant species mixtures these services can be optimised and fine-tuned to regional and farm-specific needs. Field experiments run over three years at multiple locations showed that the stability of ley performance was greater in multi-species mixtures than in legume monocultures. In addition, mixing different legume species in the  ley  helps  to  suppress  both  early  and  late  weeds.  Further,  combining  complementary phenologies of different legume species extended forage availability for key pollinator species. Finally, widening the range of legume species increases opportunities to build short term leys into rotations on conventional farms via cover cropping or undersowing.   INTRODUCTION  The demands for increasing food productivity from farmland are often seen to be in conflict with non-farmed habitats. At the same time, a similar conflict is seen to arise on farmed land itself, where crop productivity may not always easily be reconciled with the provision of other ecosystem services such as biodiversity conservation, flood amelioration, carbon storage or cultural  benefits.  In  a  three  year  study  we  asked  if  it  is  possible  to  design  a  part  of  the agricultural  ecosystem  for  simultaneous  optimization  of  productivity  and  other  ecosystem services such as biodiversity conservation.   Our approach was to use functionally diverse species-rich leys with nitrogen fixing legumes in the rotation. Nitrogen is a key nutrient to achieve acceptable yields and crop quality (Smil,  2011). Due to globally rising costs of mineral nitrogen fertilizer and concerns over the negative environmental impact of anthropogenic nitrogen  (Canfield et al., 2010), agricultural policy makers, farmers and scientists are increasingly paying attention to the use of leguminous plants as an alternative source of nitrogen. Legumes, through their symbiosis with rhizobacteria are able to fix aerial nitrogen and provide it in a form that is readily available to plants (Long,  1989). After growing legumes in a rotation, nitrogen accumulated in the plants’ above-ground and below-ground residues is broken down by microbial activity and released for the take up by the following crop. This use of legumes for fertility-building in the rotation is adopted in farming systems where the use of mineral nitrogen fertilizer is either too expensive, or, as in organic agriculture, not permitted (Watson et al., 2002). Because of its function as the main Agriculture and the Environment IX, Valuing Ecosystems: Policy, Economic and Management Interactions (2012)  151 nutrient  provider,  this  stage  in  the  rotation  is  of  central  importance  for  organic  (and  also increasingly non-organic) farming systems. Furthermore, legume-based leys provide additional benefits for soil management through soil cover and reduced soil disturbance.  Depending on climate and soil and the suitability of the land for arable production, the ley phase on organic farms can vary in duration from short term (12-18 months) to long term (around 5 years), but typically the ley is kept for about 18 months to 3 years. In Europe, organic  farmers  most  frequently  use  grass-clover  mixes  for  their  leys,  with  white  clover (Trifolium  repens),  red  clover  (T.  pratense)  being  popular  legume  species,  and  perennial ryegrass (Lolium perenne) and Italian ryegrass (L. multiflorum) as commonly chosen grass species.  Thus,  currently  used  leys  are  relatively  species-poor.  The  potential  for  nitrogen fixation by these leys is high but the establishment of simple grass-clover leys is often sub-optimal as a result of the cool, moist conditions required by white and red clover species.   In addition, the current  practice of using mixtures of red or white clover and rye-grass in fertility building leys can lead to an asynchrony between the release of nutrients following incorporation of the green manure and the demands of the following crop. One way to improve the  efficiency  of  the  system  would  be  to  combine  several  legume  species  in  a  mixture, including a number of slower growing species, that would result in a more complex residue structure with a better nutrient release profile.   In a three year study across multiple locations in the UK, we studied if ley performance and the provision of multiple ecosystem services can be simultaneously improved by exploiting the functional diversity of various legume species. In particular, we studied productivity in the ley and in the following crop, weed suppression, decomposition, pollination, and the provision of invertebrate resources for farmland birds. Here we describe the general methodology of this approach and report first results.  MATERIALS AND METHODS  Set up of Replicated Field Trials   We set up replicated field trials at six sites across the UK, evaluating various legume and grass species in  monocultures  and in  an All Species Mixture  (ASM) (Tables 1 and 2). In these experiments we trialled 18 treatments. Twelve legume species and four grass species were each grown singly as monocultures; in addition, two treatments were reserved for the All Species Mixture, which was grown with and without Rhizobium inoculation. At all six trial locations, the experiments were sown in spring 2009 (Table 2). All trials were laid out as one-factorial randomized  complete  block  designs  with  three  replications.  Seed  lots  of  the  four  clover species, the vetch, the lucerne and one of the All Species Mix treatments were inoculated with rhizobial preparations before sowing, with 1% substrate per seed weight. The locations, plot sizes,  and  sowing  dates  are  listed  in  Table  2.  Trial  sites  were  distributed  over  a  large geographical area within the UK.   To assess the after-effects of the legume species in the rotation, i.e. after incorporation of the ley plots into the soil, a cereal was grown at two sites for yield assessment (winter wheat, sown in autumn 2010 at Rothamsted and spring wheat, sown in spring 2011 at Wakelyns).   Agriculture and the Environment IX, Valuing Ecosystems: Policy, Economic and Management Interactions (2012)  152 Table 1:   Details of replicated trials: locations, plot sizes and sowing dates   North  West Altitude  (m) Plot size (m x m) Sowing date (2009) Barrington Park  51°49'52.2''  1°40'12.3''  150  1.5 x 10  20/04 Duchy  50°13'38.2''  5°18'23.0''  42  1.5 x 5  24/04 IBERS  52°25'48.1''  4°01'22.1''  29  2 x 8  23/04 Rothamsted  51°48'38.6''  0°22'02.4''  114  2 x 5  15/04 SAC Aberdeen  57°11'05.6''  2°12'45.1''  109  1.5 x 12  13/05 Wakelyns  52°21'36.7''  -1°21'09.2''  51  1.2 x 10  29/04  Table 2:   Legume and grass species included in the trials: Latin and common name; seed rate (in kg/ha), seed weight (Thousand Kernel Weight, TKW in g) and seed rate in the monoculture plots (Monoc.) and in the All Species Mix (ASM)     Seed rate (kg/ha) Abbrev.  Latin name  Common name  Monoc.  ASM  TKW AC  Trifolium hybridum  Alsike clover  10  1.25  0.7 BT  Lotus corniculatus  Birdsfoot trefoil  12  2.5  1.2 BM  Medicago lupulina  Black medic  15  2.5  1.6 CC  Trifolium incarnatum  Crimson clover  18  2.25  3.1 IR  Lolium multiflorum  Italian ryegrass  33  1  2.9 LT  Lotus pedunculatus  Large birdsfoot trefoil  12  2.5  1 LU  Medicago sativa  Lucerne  20  2.5  2.4 MF  Festuca pratensis  Meadow fescue  25  1.25  2.14 MP  Lathyrus pratensis  Meadow Pea  75  3.25  153 PR  Lolium perenne  Perennial ryegrass  33  2.5  2 RC  Trifolium pratense  Red clover  18  2.5  1.8 SF  Onobrychis viciifolia  Sainfoin  80  5  19.2 TY  Phleum pratense  Timothy  10  0.5  0.32 WC  Trifolium repens  White clover  10  1.5  0.5 SC  Melilotus alba  White sweet clover  18  0  2.3 WV  Vicia sativa  Winter vetch  100  0  41  Measurements and Assessments  At all sites a number of eco-physiological traits was measured several times during the first growing season (2009), including height, C:N ratio, and relative growth rate. In addition, at one site, Rothamsted Research, the number of pollinators and phytophagous insects supported by the different species was also recorded. Yield of the following cereals was quantified on 1 m2 per plot.  Modelling: Competition Model  A simulation model of inter-plant competition was used to predict the performance of the legumes  when  grown in  different  species mixtures.  The model used daily weather data to calculate the radiation intercepted by each species in the canopy and temperature dependent photosynthesis and growth rates. The model was validated using external datasets and was Agriculture and the Environment IX, Valuing Ecosystems: Policy, Economic and Management Interactions (2012)  153 used to predict the biomass of possible legume mixtures as well as the biomass proportions of their component species.  Modelling: Determining Functionality of Mixtures  Using regression analyses, plant traits were related to various functions (Violle et al., 2007); these  were  weed  suppression,  yield  of  the  following  crop,  regrowth,  soil  fertility,  and biodiversity value. The competition model was then used to predict the community weighted mean of different plant traits for various mixtures; this aggregated trait of the mixture is the weighted average of the traits of individual mixture components. The weights are generated by the competition model (see above) by calculating the different species’ proportions in the mix. Community weighted means of the traits can then be used to predict the function values of any mixture.  Finally,  an  aggregated  function  of  agronomic  productivity  was  calculated  as  the harmonic mean of the values for weed suppression, yield of the following crop, regrowth, soil fertility.   RESULTS  Performance of All Species Mixture in Relation to Monocultures  The  stability  of  ley  performance  was  greater  in  the  ASM  (multi-species  mixture)  than  in legume monocultures (Figure 1). The All Species Mix also showed higher weed suppression than the average of the monocultures (Döring et al., 2012).    Model Output  A  number  of  significant  relationships  between  plant  traits  and  different  agronomic  and ecological  functions  were  quantified  using  regression  analysis:  numbers  of  phytophagous insects  and  rate  of  re-growth  were  related  to  specific  leaf  area  (leaf  area/leaf  weight), abundance of pollinators to flowering traits and weed suppression to height and seed size. Winter wheat yield was significantly related to biomass of the previous legume species.   These relationships were used to predict the agronomic function and biodiversity function of the individual legume and grass species and of different mixtures. Preliminary analyses show that mixes containing both lucerne and  white clover score highly regarding the agronomic productivity function. The additional inclusion of crimson clover in such a legume-based mix will then increase the value for pollinators because of its early flowering time. In addition, this species offers to  reduce early  weed  growth  (Döring  et  al., 2012).  Importantly, the  growth pattern of crimson clover as an annual species is complementary to lucerne and white clover so that  a  mix  of  these  species  increases  resource  use  efficiency  and  reduces  interspecific competition. Finally, crimson clover emerged as a species with relatively high C:N ratio. When combined with lucerne or white clover that show lower C:N ratios, crimson clover can thereby potentially contribute to a more spread-out N supply.   Agriculture and the Environment IX, Valuing Ecosystems: Policy, Economic and Management Interactions (2012)  154   Figure 1:   Coefficient of variation (CV, %) on biomass over six trial locations (Table 1). Abbreviations of trial entries see Table 2; grasses are shown with light grey columns, legumes with white columns. The CV of the All Species Mix (ASM, dark  grey  column)  is  lower  than  the  average  CV  of  the  monocultures  (not shown)  and  it  is  also  lower  than  the  CV  of  the  average  biomass  of  the monocultures (avg mono, black column)  DISCUSSION  Mixing different legume species in the ley has several advantages: it suppresses both early and late  weeds  (Döring  et  al.,  2012);  it  extends  forage  availability  for  key  pollinator  species (Brown et al., 2012); and it increases stability of performance (see Figure 1). In addition, mixing species may help to increase the reliability of establishing the ley; further, by producing residues  with  different  carbon  to  nitrogen  ratios  mixtures  also  provide  opportunities  for modifying decomposition rates to improve the synchrony between nitrogen release following incorporation  and  crop  nitrogen  demand.  Finally,  widening  the  range  of  legume  species increases opportunities to build short term leys into rotations on conventional farms.  The simulation model used in this study has shown the potential to generate a range of optimal mixtures that deliver multiple functions. This includes new varieties of legumes, or even new species;  if  their  plant  traits  are  measured,  their  functions  can  be  determined  and  their performance in potential mixes can be predicted. Therefore, the combination of the simulation model and relationships between plant traits and ecosystem functions provides a powerful tool for  exploring  the  performance  of  a  large  number  of  mixtures  in  terms  of  the  delivery  of multiple services.        020406080100120140160180200ASMavg monoIRPRMFRCWCLUTYSCBTBMACWVMPCCLTSFCoefficient of variation (%) Trial entryAgriculture and the Environment IX, Valuing Ecosystems: Policy, Economic and Management Interactions (2012)  155 ACKNOWLEDGEMENTS  This study was carried out as part of the Legume LINK project LK09106 which was supported by the Sustainable Arable LINK programme by the Department of Environment, Food and Rural Affairs (Defra), UK. We would like to thank all farmers involved in this project for their participation and commitment, and the Organic Seed Producers for providing seed.  REFERENCES  Brown RJ, Döring TF, Storkey J, Smith J, Jones HE and Potts SG (2012). Legume based plant mixtures  for  delivery  of  ecosystem  services:  Pollinators.  In:  Valuing  Ecosystems:  Policy, Economic  and  Management  Interactions.    Proceedings  of  the  SAC  and  SEPA  Biennial Conference, Agriculture and the Environment IX, Edinburgh, 156-162 pp.  Canfield DE, Alexander N, Glazer AN and Falkowski PG (2010). The evolution and future of earth’s nitrogen cycle. Science 330, 196. Döring  TF,  Storkey  J,  Baddeley  JA,  Crowley  O,  Howlett  SA,  McCalman  H,  Pearce  H, Roderick  S  and  Jones  HE  (2012).  Legume  based  plant  mixtures  for  delivery  of  multiple ecosystem  services:  Weed  diversity  and  weed  control.      In:  Valuing  Ecosystems:  Policy, Economic  and  Management  Interactions.    Proceedings  of  the  SAC  and  SEPA  Biennial Conference, Agriculture and the Environment IX, Edinburgh, 163-168 pp.  Long SR (1989). Rhizobium-legume nodulation: Life together in the underground. Cell 56, 203-214. Smil V (2011). 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Legume based plant mixtures for delivery of ecosystem services: Pollinators. In: Valuing Ecosystems: Policy, Economic and Management Interactions.

Legume based plant mixtures for delivery of multiple ecosystem services: Weed diversity and weed control. In: Valuing Ecosystems: Policy, Economic and Management Interactions.

Let the concept of trait be functional!

Managing soil fertility in organic farming systems.

Nitrogen cycle and world food production.

Rhizobium-legume nodulation: Life together in the underground.

The evolution and future of earth’s nitrogen cycle.

Legume based plant mixtures for delivery of multiple ecosystem services: An overview of benefits

Legume based plant mixtures for delivery of multiple ecosystem services: An overview of benefits

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