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1 doi: /nture11420 Closing yield gps through nutrient nd wter mngement Nthniel D. Mueller 1, Jmes S. Gerer 1, Mtt Johnston 1, Deepk K. Ry 1, Nvin Rmnkutty 2 & Jonthn A. Foley 1 In the coming decdes, crucil chllenge for humnity will e meeting future food demnds without undermining further the integrity of the Erth s environmentl systems 1 6. Agriculturl systems re lredy mjor forces of glol environmentl degrdtion 4,7,ut popultion growth nd incresing consumption of clorie- nd met-intensive diets re expected to roughly doule humn food demnd y 2050 (ref. 3). Responding to these pressures, there is incresing focus on sustinle intensifiction s mens to increse yields on underperforming lndscpes while simultneously decresing the environmentl impcts of griculturl systems 2 4,8 11. However, it is uncler wht such efforts might entil for the future of glol griculturl lndscpes. Here we present glol-scle ssessment of intensifiction prospects from closing yield gps (differences etween oserved yields nd those ttinle in given region), the sptil ptterns of griculturl mngement prctices nd yield limittion, nd the mngement chnges tht my e necessry to chieve incresed yields. We find tht glol yield vriility is hevily controlled y fertilizer use, irrigtion nd climte. Lrge production increses (45% to 70% for most crops) re possile from closing yield gps to 100% of ttinle yields, nd the chnges to mngement prctices tht re needed to close yield gps vry considerly y region nd current intensity. Furthermore, we find tht there re lrge opportunities to reduce the environmentl impct of griculture y eliminting nutrient overuse, while still llowing n pproximtely 30% increse in production of mjor cerels (mize, whet nd rice). Meeting the food security nd sustinility chllenges of the coming decdes is possile, ut will require considerle chnges in nutrient nd wter mngement. Opportunities for griculturl intensifiction were nlysed for seventeen mjor crops (which covered pproximtely 76% of glol hrvested croplnd re etween 1997 nd 2003 (Food nd Agriculture Orgniztion of the United Ntions)). Yield gps (Fig. 1) were estimted y compring lndscpe-level oserved yields 12 to ttinle yields, determined y identifying high-yielding res within zones of similr climte. As empiricl estimtes, ttinle yields re more conservtive thn solute iophysicl potentil yields 13, ut they re proly chievle using current technology nd mngement techniques. Considerle yield-improvement opportunities exist reltive to current ttinle yield ceilings, with opportunities differing drmticlly y crop nd geogrphy (regionl nd country-specific dt for ll seventeen crops re summrized in the Supplementry Informtion). Glolly, we find tht closing yield gps to 100% of ttinle yields could increse worldwide crop production y 45% to 70% for most mjor crops (with 64%, 71% nd 47% increses for mize, whet nd rice, respectively). Estern Europe nd Su-Shrn Afric show considerle low-hnging intensifiction opportunities for mjor cerels (Fig. 2); these res could hve lrge production gins if yields were incresed to only 50% of ttinle yields. Est nd South Asi lso hve sustntil intensifiction opportunities owing to their vst griculturl lnds nd the geogrphic vriility in their yields nd yield gps. Assessing opportunities for more sustinle intensifiction requires n understnding of the fctors driving yield vrition cross the world. Fundmentlly, yield gps re cused y deficiencies in the iophysicl crop growth environment tht re not ddressed y griculturl mngement prctices. Here we explicitly exmined key iophysicl drivers of crop yield y using glol, crop-specific irrigtion dt 14 nd y developing new glol, crop-specific dt set of nitrogen (N), phosphte (P 2 O 5 ) nd potsh (K 2 O) fertilizer ppliction rtes. We find extensive geogrphic vrition in these mngement prctices, with high fertilizer ppliction rtes concentrted in high-income nd some rpidly developing countries (Fig. 3 nd Supplementry Fig. 1). Likewise, irrigted res 14 re hevily concentrted in South Asi, Est Asi nd prts of the United Sttes (Fig. 3). Using input yield crop models, we found tht the sptil ptterns of climte, fertilizer ppliction nd irrigted re explin 60% to 80% of glol-yield vriility for most mjor crops (Supplementry Informtion nd Supplementry Tle 1). Yields of some crops (for exmple, sorghum, millet nd groundnut) were primrily controlled y climte, wheres others (for exmple, rley, sugr eet nd oil plm) showed strong mngement responses. Surprisingly, model residuls showed little sensitivity to soil nd slope prmeters (Supplementry Informtion nd Supplementry Fig. 2), suggesting tht such reltionships re oscured on the lndscpe scle with existing dt sets. The fctors tht primrily limit incresing crop yields to within 75% of their ttinle yields (Fig. 4, Supplementry Fig. 3) vry y crop nd region. For exmple, Estern Europe nd West Afric stnd out s hotspots of nutrient limittion for mize, wheres Estern Europe seems to experience nutrient limittion for whet. Co-limittion of nutrients nd wter is oserved cross Est Afric nd Western Indi for mize, portions of the US Gret Plins nd the Mjor cerels: ttinle yield chieved (%) Figure 1 Averge yield gps for mize, whet nd rice. These were mesured s percentge of the ttinle yield chieved circ the yer Yield gp in ech grid cell is clculted s n re-weighted verge cross the crops nd is displyed on the top 98% of growing re. 1 Institute on the Environment (IonE), University of Minnesot, St. Pul, Minnesot 55108, USA. 2 Deprtment of Geogrphy nd Glol Environmentl nd Climte Chnge Center, McGill University, Montrel, Queec H3A 2K6, Cnd N AT U R E V O L O C T O B E R Mcmilln Pulishers Limited. All rights reserved

2 RESEARCH Crop production (illion tonnes) Production circ the yer 2000 Incresed production; yield gps closed to 50% of ttinle yields Incresed production; yield gps closed to 75% of ttinle yields Incresed production; yield gps closed to 90% of ttinle yields Incresed production; yield gps closed to 100% of ttinle yields M W R M W R M W R M W R M W R M W R M W R M W R M W R North Americ Ltin Americ Western Europe Estern Europe Middle Est nd Su Shrn South Asi Est Asi Southest Asi nd Crien nd Centrl Asi North Afric Afric nd Oceni Region nd crop Figure 2 Glol production increses for mize, whet nd rice from closing yield gps to 50%, 75%, 90% nd 100% of ttinle yields. The gretest opportunities for increses in solute production (from closing yield gps to 100% of estimted ttinle yields) re whet (W) in Estern Europe nd Centrl Asi, rice (R) in South Asi nd mize (M) in Est Asi. Asolute production increses for individul crops in Su-Shrn Afric re smller owing to lower ttinle yields nd diverse cropping systems (tht is, less re devoted to ny one crop). The region could still chieve lrge production increses in cssv, mize nd sugrcne. Mediterrnen Bsin for whet, nd in Southest Asi for rice. We note tht the mngement prctices tht limit yield increses depend on the degree of yield-gp closure desired (Supplementry Fig. 4). For exmple, closing mize yield gps to 50% of ttinle yields (pproximtely 2.5 tonnes per hectre) in Su-Shrn Afric primrily requires ddressing nutrient deficiencies (Supplementry Fig. 4), ut closing yield gps to 75% of ttinle yields (pproximtely 3.6 tonnes per hectre) requires increses in oth irrigted re nd nutrient ppliction over most of the region (Fig. 4). We exmined potentil chnges in irrigted re nd nutrient ppliction tht re needed to close yield gps of mize, whet nd rice to within 75% ttinle yields ( 29% glol production increse) using our input yield models. On the lndscpe scle, yield gps in colimited regions cn e closed through rnge of irrigted-re nd nutrient-intensity comintions (see Supplementry Fig. 5). For exmple, 73% of these underchieving res could close yield gps y solely focusing on nutrient inputs (with 18%, 16% nd 35% increses in N, P 2 O 5 nd K 2 O ppliction reltive to seline glol consumption, respectively), wheres only 16% of underchieving res could close yield gps y solely incresing irrigtion. Jointly incresing irrigted re nd nutrient ppliction could close yield gps on ll underchieving res (with 30%, 27% nd 54% increses in N, P 2 O 5 nd K 2 O ppliction, respectively, nd 25% increse in irrigted hectres; Fig. 5, ). To minimize the environmentl impcts of intensifiction, incresed irrigtion nd nutrient ppliction to close crop yield gps should e complemented y efforts to decrese overuse of crop inputs wherever possile ; comined, these efforts could increse totl food production while decresing the overll glol use of wter nd nutrients. For exmple, we estimte tht y ddressing imlnces nd inefficiencies, nitrogen- nd phosphte-fertilizer ppliction on mize, whet nd rice could decrese glolly y 11 million tonnes of nitrogen (28%) nd 5 million tonnes of phosphte (38%) without impcting current yields (Supplementry Fig. 6). Nutrient overuse on these crops is prticulrly drmtic in Chin, confirming field-scle results 15. To close yield gps to 75% of ttinle yields while lso eliminting input overuse (under joint nutrient nd irrigtion intervention), we project tht smller net chnges in nutrient inputs would e required: 9%, 22% nd 34% chnges in N, P 2 O 5 nd K 2 O ppliction (Fig. 5c nd Supplementry Fig. 7). Notly, it would e possile to close glol yield gps on mjor cerels to within 75% of ttinle yields with firly miniml chnges to totl worldwide nitrogen nd phosphte use y coupling trgeted intensifiction with efforts to reduce nutrient imlnces nd inefficiencies. Geogrphiclly optimizing input intensity nd incresing field-scle efficiencies (eyond the verge efficiencies implicit in our input yield models) could improve production further reltive to inputs. Closing yield gps my not lwys e desirle or prcticl in the short term, given mrginl returns for dditionl inputs, regionl Mjor cerels: verge N fertilizer ppliction rte (kg N h 1 ) Mjor cerels: re irrigted (%) Figure 3 Mngement intensity of nitrogen fertilizer nd irrigted re 14 vries widely cross the world s croplnds.,, Fertilizer () nd irrigtion () vlues re re-weighted verges cross mjor cerels. 11 OCTOBER 2012 VOL 490 NATURE 255 Mcmilln Pulishers Limited. All rights reserved

3 RESEARCH LETTER Nutrient nd irrigtion limited 75% ttinle yields chieved Nutrient nd irrigtion limited 75% ttinle yields chieved c Mjor cerels: Δ% irrigted re c Nutrient nd irrigtion limited 75% ttinle yields chieved Figure 4 Mngement fctors limiting yield-gp closure to 75% of ttinle yields for mize, whet nd rice.,, c Yield-limiting mngement fctors for mize (), whet () nd rice (c) were clculted using the suite of input yield models, compring current input intensity ginst estimted required levels to close yield gps. lnd-mngement policies, limits on sustinle wter resources nd socio-economic constrints (for exmple, ccess to cpitl, infrstructure, institutions nd politicl stility). However, use of precision griculture techniques, conservtion tillge, high-yielding hyrids, incresed plnt popultions nd multifunctionl lndscpe mngement cn help to mitigte negtive environmentl impcts of intensive griculture Additionlly, use of orgnic fertilizers (omitted in this nlysis owing to dt limittions) re essentil for improving soil cron, enhncing soil iot nd incresing wter-holding cpcity 22. Socil triggers of intensifiction will differ cross regions; for exmple, ecuse of development interventions y governments or NGOs, mrket-driven incentives for frmer investment, nd lnd scrcity in regions not fully connected to glol mrkets 23. Chnges to griculturl mngement to close yield gps should e considered in the context of climte chnge, which is expected to sustntilly impct yields 24,25 nd induce mngement dpttions 26. Specificlly, mjor concern is how chnges in wter vilility my conflict with projected irrigtion requirements for closing yield gps. Mjor cerels: ΔN ppliction rte (kg h 1 ) Figure 5 Closing yield gps through chnges in griculturl mngement.,, Projected increses in nitrogen ppliction rtes () nd irrigted res () necessry to close mize, whet nd rice yield gps to 75% of ttinle yields. c, Projected net chnges in nitrogen ppliction rtes when closing yield gps nd eliminting input imlnces nd inefficiencies. The fertilizer dt set, yield gp estimtes nd yield models presented here could e used widely to ssess intensifiction opportunities nd the environmentl impcts of chnging griculturl systems. However, these dt nd nlyses re not without limittions (full discussion in Supplementry Informtion). Most importntly, the nlyses rely on griculturl mngement, yield nd climte dt from vriety of different sources nd on different scles. Overll, these results re most useful cross regionl nd glol scles, leving finescle nd temporl detils oscured (for exmple, intr- nd internnul vrition in climte nd yield cretes prticulr uncertinty out irrigtion requirements). Moreover, lthough our models N AT U R E V O L O C T O B E R Mcmilln Pulishers Limited. All rights reserved

4 RESEARCH confirm the importnce of climte, fertilizers nd irrigtion in determining contemporry ptterns of glol croplnd productivity, we do not discount the importnce of dditionl iophysicl chrcteristics (including soil chrcteristics, see Supplementry Informtion) nd mngement prctices (including crop rottion ptterns, orgnic nutrient inputs, micronutrients, improved seed qulity, conservtion tillge nd pest mngement). Incorporting these fctors into the nlyticl frmework could improve the ccurcy nd utility of the nlyses. Additionl reserch on croplnd intensifiction must lso ssess the opportunities nd environmentl trdeoffs for incresing cropping intensity nd decresing pre- nd post-hrvest crop losses. The future of griculture fces two gret chllenges: sustntil increses in food demnd must e met while decresing griculture s glol environmentl footprint. Closing yield gps nd incresing resource efficiency re necessry strtegies towrds meeting this chllenge, ut they must e comined with efforts to hlt griculturl expnsion, reduce food wste nd promote sensile diets, nd produce dvnced crop vrieties 1,4. This nlysis emphsizes the crucil role of nutrient nd wter mngement in pthwys towrds sustinle intensifiction, nd provides strting point for more comprehensive discussion of intensifiction opportunities nd chllenges. Contextdependent policies nd griculturl development progrms must ddress drivers of yield limittion while encourging mngement prctices tht improve trdeoffs etween production nd environmentl impcts. METHODS SUMMARY Yield gps were quntified y compring existing yields to climte-specific ttinle yields. Our pproch refines previous estimtes 27,28 y excluding climte outliers nd using crop-specific, equl-re climte zones. Fertilizer ppliction rte nd consumption dt were compiled for ntions nd suntionl units cross the gloe (Supplementry Tle 2). Appliction rtes for crop country comintions missing dt were estimted s descried in the Supplementry Informtion. Crop- nd crop-group-specific ppliction rtes were then distriuted cross detiled mps of crop 12 nd psture 29 res, nd rtes were hrmonized with suntionl nd ntionl nutrient consumption dt. Fertilizer nd irrigtion dt were used to prmeterize nutrient response curves nd rinfed mximum yields, using nonliner regression nlyses within ech climte zone. Using these reltionships, we estimted chnges in inputs necessry to close yield gps, s well s decreses in inputs possile from ddressing inefficiencies nd imlnces. Received 2 April; ccepted 13 July Pulished online 29 August; corrected online 10 Octoer Godfry, H. C. J. et l. Food security: the chllenge of feeding 9 illion people. Science 327, Royl Society Reping the enefits (The Royl Society, 2009). 3. 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Comininghighiodiversitywith highyieldsintropicl groforests. Proc. Ntl Acd. Sci. USA 1 6 (2011). 11. Burney, J. A., Dvis, S. J. & Loell, D. B. Greenhouse gs mitigtion y griculturl intensifiction. Proc. Ntl Acd. Sci. USA 107, Monfred, C., Rmnkutty, N. & Foley, J. A. Frming the plnet: 2. Geogrphic distriution of crop res, yields, physiologicl types, nd net primry production in the yer Glo. Biogeochem. Cycles 22, GB1022 (2008). 13. Loell, D. B., Cssmn, K. G. & Field, C. B. Crop yield gps: their importnce, mgnitudes, nd cuses. Annu. Rev. Environ. Resour. 34, (2009). 14. Portmnn, F. T., Sieert, S. & Doell, P. MIRCA2000 glol monthly irrigted nd rinfed crop res round the yer 2000: new high-resolution dt set for griculturl nd hydrologicl modeling. Glo. Biogeochem. Cycles 24, GB Ju, X.-T. et l. Reducing environmentl risk y improving N mngement in intensive Chinese griculturl systems. Proc. Ntl Acd. Sci. USA 106, (2009). 16. Liu, J. et l. 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Contriution ofworkinggroup II to the Fourth Assessment Report of the Intergovernmentl Pnel on Climte Chnge (eds Prry, M. L., Cnzini, O. F., Plutikof, J. P., vn der Linden, P. J. nd Hnson, C. E.) (Cmridge Univ. Press, 2007). 25. Loell, D. B., Schlenker, W. & Cost-Roerts, J. Climte trends nd glol crop production since Science 333, (2011). 26. Howden, S. M. et l. Adpting griculture to climte chnge. Proc. Ntl Acd. Sci. USA 104, (2007). 27. Licker, R. et l. Mind the gp: how do climte ndgriculturl mngement explin the yield gp of croplnds round the world? Glo. Ecol. Biogeogr. 19, Johnston, M. et l. Closing the gp: glol potentil for incresing iofuel production through griculturl intensifiction. Environ. Res. Lett. 6, (2011). 29. Rmnkutty, N., Evn, A. T., Monfred, C. & Foley, J. A. Frming the plnet: 1. Geogrphic distriution of glol griculturl lnds in the yer Glo. Biogeochem. Cycles 22, GB1003 (2008). Supplementry Informtion is ville in the online version of the pper. Acknowledgements We thnk G. Allez nd K. Millign for ssistnce with dt collection. We re grteful to R. Licker, G. McDonld, M. Mueller, S. Polsky, P. Potter, P. Reich, L. Schulte-Moore, D. Tilmn, J. Vn Wrt nd the Foley Lortory for helpful converstions. We thnk P. Roertson nd P. Smith for helpful comments on the mnuscript. Funding ws provided y Ntionl Science Foundtion Grdute Reserch Fellowship nd University of Minnesot College of Food, Agriculturl nd Nturl Resource Sciences Fellowship to N.D.M., Nturl Sciences nd Engineering Reserch Council (NSERC) of Cnd Discovery Grnt to N.R., Gordon nd Betty Moore Foundtion funding to J.A.F., nd support from the University of Minnesot Institute on the Environment. Author Contriutions N.D.M. led the study design, dt nlysis nd writing. J.S.G. contriuted sustntilly to the yield-gp dt nlysis nd writing. D.K.R. nd M.J. ssisted with dt nlysis nd writing. J.A.F. nd N.R. ssisted with study design nd writing. Author Informtion Reprints nd permissions informtion is ville t The uthors declre no competing finncil interests. Reders re welcome to comment on the online version of the pper. Correspondence nd requests for mterils should e ddressed to N.D.M. (muell512@umn.edu). 11 OCTOBER 2012 VOL 490 NATURE 257 Mcmilln Pulishers Limited. All rights reserved

5 CORRECTIONS & AMENDMENTS CORRIGENDUM doi: /nture11907 Corrigendum: Closing yield gps through nutrient nd wter mngement Nthniel D. Mueller, Jmes S. Gerer, Mtt Johnston, Deepk K. Ry, Nvin Rmnkutty & Jonthn A. Foley Nture 490, (2012); doi: /nture11420 In this Letter, minor error in the mpping progrm used to generte Fig. 1 incorrectly displyed reduced yield gp estimtes cross few res; this ws most pprent in the Shel region of Afric. The corrected Fig. 1 is shown elow. This error does not ffect the results or conclusion of the pper, nd hs een corrected in the HTML nd PDF of the originl pper. Mjor cerels: ttinle yield chieved (%) 390 NATURE VOL FEBRUARY 2013 Mcmilln Pulishers Limited. All rights reserved