BIOLOGICAL NITROGEN FIXATION RETURNS TO EUROPEAN AGRICULTURE

Transcription

1 BIOLOGICAL NITROGEN FIXATION RETURNS TO EUROPEAN AGRICULTURE Fred Stoddard Frederick (dot) stoddard (ät) helsinki (dot) fi Stoddard: BNF returns to Europe

2 BIOLOGICAL NITROGEN FIXATION RETURNS TO EUROPEAN AGRICULTURE Fred Stoddard Frederick (dot) stoddard (ät) helsinki (dot) fi Stoddard: BNF returns to Europe

3 What is BNF and who cares? Legumes for BNF and other purposes Changes in use of legumes in Europe Environmental trade-offs The future Stoddard: BNF returns to Europe

4 What is BNF? Symbiosis between bacterium and host plant Some other forms, such as cyanobacteria Bacterial nitrogenase reduces N 2 to NH 4 + High energy input (16 ATP per N 2 ) using host-plant photosynthate Present in alder trees (Alnus), seabuckthorn (Hippophaë) and LEGUMES (Fabaceae) In root nodules, with rhizobium Stoddard: BNF returns to Europe

5 N fertilizer (Tg) Who cares? You do! 120 Reactive N is needed in food (protein) 100 World Total yearly natural nitrogen fixation = x g (Tg, million t) on land, Tg in oceans 1909: Haber-Bosch process: 200 C, 200 atmospheres, Fe catalyst: N H 2 2 NH 3 ~1 t fossil fuel per t fertilizer = 1.3% of total fossil fuel consumption ~1.2% escapes as N 2 O, x more powerful greenhouse gas than CO Rest of world N America, Europe, Australasia Data from FAOstat Stoddard: BNF returns to Europe

6 N demand or availability (arbitrary units) Fertilizer N availability is seldom coordinated with plant demand Applied fertilizer availability Potential for NO 3- leaching, N 2 O emission Crop residue breakdown 5 0 Crop N demand Month Stoddard: BNF returns to Europe

7 Legumes fix N as they need it and offer more besides FAO views legumes as one of the 5 pillars of Sustainable (or Ecological) Intensification BNF And associated changes in soil biology Break-crop effects Allow soil-borne diseases of cereals to die Different biology allows use of alternative weed & pest control chemistry & methods Support of pollinator populations Stoddard: BNF returns to Europe

8 Legumes can make use of bound phosphorus Most long-term agricultural soils contain plentiful phosphorus in plant-unavailable forms Roots release organic acids From faba bean, citric and malic acids These release PO 4 from bound forms e.g., Ca 3 (PO 4 ) 2 or Fe 3 (PO 4 ) 2 Faba bean accessions differ 3x in P acquisition ability i.e., some are more independent of P fertilizer than others Effects continue in next wheat crop (Western Australia, pot experiment) Wheat P uptake benefits from strong release of P by preceding faba bean Strip intercrops of faba bean and maize in China enhance each other s P and N uptake Stoddard: BNF returns to Europe

9 All crops are protein crops, but some are more protein than others Crop Global crop production (million t, Tg) Mean % protein (DM basis) Maize Wheat Rice Barley Soybean Global protein production (Tg) (DM basis) FAOstat data for 11-12% moisture Feedipedia.org Stoddard: BNF returns to Europe

10 Production or import (Million t) Nevertheless, Europe imports a LOT of legume protein Mostly soybean for pig & poultry feed < 10% soy for food 70% of protein supplement = 16% of total feed protein imported Food pulses largely imported (0.4 M t common bean, 0.2 M t lentil and chickpea, M t pea but 0.4 M t faba exported) Soybean imports (net) Pulse production Pig meat Poultry meat Ruminant meat Stoddard: BNF returns to Europe

11 So we spoke to the European Parliament in 2013 Crop and soil sciences, economics, sociology Stoddard: BNF returns to Europe

12 Area (thousand ha) Production (Tg, million t) Result: Revised CAP helps grain legume areas % 12x 128% 52% % 11x 239% 35% 0 77% Area 2009 Area % Production 2009 Production 2016 Pea Faba bean Lupins Other pulses Soybean Pea Faba bean Lupins Other pulses Soybean Stoddard: BNF returns to Europe

13 Summary of changes Areas more than doubled in 7 years 17x in Bulgaria, 16x in Latvia, 11x in Estonia, no change in UK Production less than doubled Mean yield (t/ha) of pea, faba bean, soybean and other pulses (chickpea, lentil, common bean) all went down Lupin mean yields went up 50% Novices do not achieve good yields Legume crops are challenging Alfalfa areas up 4%, production up 30% Harvest for feed pellets Other forage (clovers, trefoils, etc) areas up 22%, production down 5% Biggest increases in Poland Harvest is specialized Stoddard: BNF returns to Europe

14 Are diets changing, too? Nutritionists claim that average meat consumption is too high Flexitarians New foods appearing in many countries Nyhtökaura, Pulled oat, of oat + pea + faba bean protein, texturized Extrudates of faba bean (Finland), chickpea (several countries) Tempeh from other beans than soybean 2.5-fold increase in pulse consumption in USA in 2016 Stoddard: BNF returns to Europe

15 What makes legumes special in the diet? Higher protein content than cereals (20-50% instead of 7-15%) Amino acid composition: rich in lysine, poor in S-containing amino acids, complementing cereals Slowly digestible starch 15-20% dietary fibre (more in lupins) Bioactive substances: flavonoids, tocols, carotenoids, sterols, tannins, saponins Oil composition mostly linoleic and linolenic acids Rich in Ca, Mg, Fe, Zn Storage protein mostly globulin, soluble in weakly saline solution Hence soy milk, yoghurt, tofu Do the same with other legumes Endogenous lipoxygenase is detrimental to flavour, activates in wet processes Can be denatured by heat treatment of dry seeds Reduced by breeding of soybean, pea Lupin-based ice cream in Germany, experimental cream cheese in Finland Faba bean milk and yoghurt soon? Stoddard: BNF returns to Europe

16 Imperfections Oligosaccharides: sucrose galactose units Not digested by monogastrics Fermented in colon: gas, sometimes diarrhoea Alpha-galactosidase added to pigfeed, can be bought at pharmacies for food use Could ultrafiltration of milk work? Trypsin inhibitors require cooking Almost all legumes at maturity Protection from many seed weevils Reduced by breeding in feed-grade pea Other antinutrients: Phytohaemagglutinins in common bean Denatured by cooking Other legumes have weaker lectins Alkaloids in lupins Reduced by breeding Vicine-convicine (favism factors) in faba bean Reduced by breeding Eliminated by glucosidase + acidity (sourdough) Stoddard: BNF returns to Europe

17 Estimating BNF on the continental scale in grain legumes Grain yield data taken from FAOstat and Eurostat (>10-fold range) Use literature values for each species for harvest index, to estimate above-ground biomass, root:shoot ratio, for below-ground biomass, [protein], N harvest index, root [N], for total N mass, rhizodeposition, for N leakage This gives total N per kg of grain Ndfa (proportion of N derived from atmosphere) Multiply by yield to get estimate for country or continent Stoddard: BNF returns to Europe

18 Sample results (per tonne (Mg) of grain) Faba bean (29% protein) Pea (23% protein) Soybean (39% protein) Ndfa (ratio) N in grain (kg) Total plant N (kg) N fixed (kg) N balance (kg) Residual N (kg) So a 3-tonne crop of faba bean leaves 66 kg of freshly fixed N, but a 3-tonne crop of soya takes 14 kg from soil N reserves Stoddard: BNF returns to Europe

19 Total 206 thousand t (Gg) of N fixed in Europe in 2009 Vetches Chickpea Common bean Soya bean Faba bean Pea Lentil Lupin Stoddard: BNF returns to Europe

20 N balance (Gg) N balance across Europe (fixation harvest, thousand t) in 2009: total 37 Gg Chickpea Common bean Faba bean Lentil Lupin Pea Soya bean Vetches Stoddard: BNF returns to Europe

21 What about forage legumes? Forage area data from Eurostat Separate permanent and temporary grassland N retention in fields from CAPRI (Common Agricultural Policy Regionalized Impact model) N fixation coefficient derived from typical Ndfa data for clovers and alfalfa and legume content of the fields Content of legumes in forages was estimated by Legume Futures experts Stoddard: BNF returns to Europe

22 Austria Belgium & Lux Bulgaria Cyprus Czech Rep Denmark Estonia Finland France Germany Greece Hungary Ireland Italy Lithuania Latvia Malta Netherlands Poland Portugal Romania Slovakia Slovenia Spain Sweden UK N fixation (Gg) Total: t of N fixed in forage grasslands in Permanent Temporary Stoddard: BNF returns to Europe

23 Final calculations Alfalfa grown in pure stands for pellets, mostly with irrigation in Italy and Spain Area and production data from Eurostat 29 Tg in 65% dry matter content 19 Tg of DM, 2.5% N, 80% Ndfa = 375 Gg of N fixed Alternative model: N = x DM, + 17 kg / ha = 397 Gg of N fixed 35 Tg in Gg of N In total, = 1172 Gg of N fixed in 2009 Estimates for 2016: = 1560 Gg Data for allocation of other among common bean, chickpea, lentil and vetches not available N balance from grain legumes 66 Gg Stoddard: BNF returns to Europe

24 What does this mean in practice? It is NOT fertilizer saved It is low-cost input into animal feed (forage) or feed and food (grain) with minimal usage of fossil fuel The N balance could be fertilizer saved, but most European farmers view it as a bonus rather than a saving What happens if we aim to increase protein security by producing more and importing less? What crops are displaced? What happens if diets change so less needs to be imported for feed? N fixation is a reduction process from N 2 to NH 4 + No oxygen, no N 2 O intermediate In itself, does not contribute to N 2 O emission Stoddard: BNF returns to Europe

25 Drawbacks and trade-offs Legume residues have a high N content, so a low C:N ratio, and break down rapidly Thus high potential for NO 3- leaching, N 2 O emission after the crop Since inputs to the legume are low, need to measure the environmental impacts over a whole rotation This shows that N escape is lowered by the legume Prices are often too low to compensate for the currently low yield Food use usually commands a higher price than feed use Manure-rich regions need to be able to dispose of animal waste so the N gets mopped up by a demanding cereal or oilseed Stoddard: BNF returns to Europe

26 How to trap more of the biologically fixed N or prevent emission Rhizobium bacteria with the nosz gene for Nitrous oxide reductase reduce N 2 O release as residues break down So do some other denitrifying bacteria: inoculate? Root exudates alter the denitrifying environment: scope for breeding or management Application of C-rich material to alter the C:N balance: cereal straw or biochar Cover crops (hard in the Nordic-Baltic region, easier elsewhere) to take up N as it mineralizes Investment in breeding for yield, stress resistance, disease resistance, quality Stoddard: BNF returns to Europe

27 What should we grow where? Feed manufacturers want soybean 39% protein and 18% oil better amino acid composition than most legumes Soy is a warm-temperate crop, as is common bean: needs warmth and water Elsewhere, cool-temperate crops such as faba bean and pea deliver higher protein yields with more reliability Faba, pea and lupins for protein processing Lentil and chickpea for easy food use Soybean Metzger et al 2007 Stoddard: BNF returns to Europe

28 WILL LEGUMES SAVE AGRICULTURE? (with a little help from their microbe friends) Stoddard: BNF returns to Europe

29 YES [end of talk] [tumultuous applause] Stoddard: BNF returns to Europe

30 Acknowledgments EU-funded FP7 project, And especially Prof Christine Watson, SRUC Scotland; Dr Göran Bergkvist, SLU Sweden; Mr Moritz Reckling, ZALF Germany FACCE ERA-NET+ project, EIP-AGRI focus group on protein crops, Stoddard: BNF returns to Europe

31 Advertisement Published May pages ISBN online from CABI Stoddard: BNF returns to Europe