E.or.nln R.ltn\ 3l(l). 1979. pp. 172 18,1(O J980. hy the Ncr York Bo l .n ica l Cr r lcn . Brn t . NY I0 ,1 j8

USI]S AND POTENTIAL USES OF LECUMINOUS 'I'R!]ES FORMINIMAI, ENERGY INPU'T AGR]CULTURE

I Depanmcnt of Soil and Linvironmenlal Scienc€s. Unilcrsity of California, Riverside, California92521

: Depanment of Borany and Pllnt Patholoey. Michisan Strtc Universily, Easl Lansins, Michisan,18824.

P I T L : R F E L K E R 1 ^ N D R o R E R T S . B A N D U R S K I '

Lcsunrinous l.cc o.chuds tirc propo\ed as !n lgricullurrl systcm rc.luhingdlninaljnput ofaossil tucl. nrachnre.y. rnd $pital. Lcsume orchards lix nilr)Een.rquirc ncithe. rillase nor irrigaln'n. and, polenlially. trovjdc lartc yiclds of nu-tliliors nods. Funhe.. our itnnlyli.rl d.la show sccd protcin conlcnls rangingrrom 16 lo 69 percent. wirh .nc spccics hrling nn .mino ac prolile slfernr torhd o l casc in .

what crops wiu be grown for food and liveslock feed when the petroleumsuppl ies are gone? Nei lher developcd nor developing nat ions can suslain agricul tures based upon mass;ve inpuls of fossi l fuel energy (1. 2. 3. 4. 5). PossiblyuDl imited nuclea. cncrgy wi l l become avai lable to supply energy to pump water.d ve traclors and synthesize intensively energy-demanding nitrogenous fertilizcrsso that current agr icul tural pract ices wi l l be l i tdc modif ied. Perhaps crops in useloday will continlre 1() be grown but with a rclDrn lo the labor-intensive agricul-lufe of 100 years ago. Al lernal ively, convcnl ional ccrcal crops may be mod-i f ied lhrough plant breeding or gen€t ic enginccr ing to el iminate dependencyupon l i l lagc and upon ni l rogcn I ixed by cnergy- intensive industr ial processes.However. i1 is also possible thal there wi l l be increased dependency upon"altefnai ive ag cul tures," incorporat ing plants and t i l lage pract ices that arenot widespfead ioday. We focus attent ion upon lhis lat ter possibi l i ty . rnd askwhether there are plants useable for fbod and fbed, whose physiological. ecolog-ical. and mofphologic characteristics obviate the need for tillage. irrigation andfertilization and provide high yields of protein'rich food. To help identify suchplants. if in fact they exist, we developed an idiolype with the following char-acler ist ics: I ) growth condit ions that cause minimal soi l and nutr ient loss. 2) l i t t leor no need for i r r igat ion, l ) high yield,4) abi l i ty to l ix ni t rogen and 5) product ionof large amounts of high quality protein. Next, wc madc an assessment of foodproducing plants and found that lree legumes have the characteristics of theidiotype. Furlher. we have shown. by prolein and amino acid analysis, that thereis suff ic ient senet ic diversi ty among the tree legumes to permit select ion for aprotein of amino acid composit ion supcrior to, cvcn, mi lk casein!

I t ;s the intent of this communicat ion to focus attent ion upon the possibleadvantages of an alternative agriculturc, 10 indicatc some desirable attributes ofsuch an agriculturc and to determine what new data would be required before analternative ngricullure could be developed. I1 must be emphasized that quantitative measurements of yield, nitrogen fixrtion, and drought resistance are oftennot available. This is because many of the uses of tree legumes to which weallude occur in developins areas of the world and have not been the subject ofextensive research. However, on the basis of data curently available, it appearsthat an orchard ofleguminous trees with aperennial soil cover would most closelyapproximate the ideal crop for minimal energy input agriculture.

Mitlinization oJ soil and nutiant /orr. This is best attained by utilizing anuntilled per€nnial lre€ or shrub crop with some grass cover. The importance of

F I I KFR & I ] \ ] JURS | \ I L I 'UMINUL ]S IRT IS

perennial cover in conscrving mineral nutrients is demonstrated bv rhe HubbardB r o u k p r o J e c ' r 6 , $ h i c h . h o u ( d r h a r m i n e r a t J n J \ a t r e m u \ f r o m a n a r e a d e n u J e dof lbrest vegetarion was ,{0-fold higher than the control for nirrate. l5 for Dotas,srum. fuur for cdlci .m and m"gnc\rum. and lwo for .odium. The e,r imared r imetbr los! of eight inches of surfacc soil in mid-wesr America is l7 years with non-contour tillage and 2231 years wirhout tillage (7). Similar resutrs were reporredfor an African foresl ecosystem (8). An additionat fearure ofa perenniat soii coveris that a no, l i l lage system does nor requjre fuel , machinery, and the backup\upporr required by mechJnr, ,ul iL)n.

N?t,l -fbt i,rig.ttior. Suflicjent tolerancc to drought to obviate the .eed forirrigation is an imporranr facror in reducing needs for capital and energy inpul(4,5)- Woody xerophyt ic tree legumes are wel l adapred to ar id cl imares (9. t0,ll, 12) perhaps because their tap rools. which reach 20 m in lengrh, often reachground water (13). Crassulacean acjd merabol ism (CAM). which reduces waterstress, would be a desirable characrerisiic in crops of arid regions. The report( l4J oI CAM in P/ r \ ' r r ; \ require. conf irmdrion. t

Mtuinlunt rit4.l.-Forest ecosystems are among rhose with rhe highest netannual producriv i ly (15. 16). This r jeems to be due to muhiple lavers of teaves.plu\ rhc rrniJ ir \ with whrch d complere. t ighr Jbsorbing teal canopy can be establ ished.Anuddit ionalfcatureoftreeecosyslemsisrhatnetannualDroduct iv i tvr. hirh. bur fef t i l i /er rcquiremenr\ rre of len bdrcl ' ( le jnon\ lrrble ( ta, I8) becau!;l h e n i l r o g c n r \ r c ( \ r l e d t h r o u g h o r g d n i c m a l l e r . B e c a u \ e p r o J u c r i \ i t y i s , o g r e a t .there is the possibi l i ty rhat rhis growlh can be siphoned off into edible Dorr ionsor u\eJ for animal feel l . Af ier rhe rree. have pa\\eJ lhe rgc of ma\im m podprodrctivity. they may be useful for hcaring and cookins fuet.

Abilit! to.lix ittas" .-Tbe idiorype shoutd be a nirrogen,fixer bccause seedsol nitrogen-fixing plants are often higher in protein than those of non-fixcrs andbecause nodulation would rcduce needs fbr fertilizer nirrosen.

l t , . l t ' , ! t , " t , ' I r ' t r t i . - Ihe idiolype \houtJ havc a hich yiet . l of prorein ofwhich the amino acid composit ion should be as close as possjble 1() that recom-m e n d r d f o ' h u m a n n u r r i l i o n . e ! e n r h o u g h o r h e r f o o d s $ i , o f c u u r r e , b e e a r e nto complemcnl lhe legrmc amino acid prof i le.

THI ] IDEAL CROP

Using thc above parameters. it becamc apparent that tree Iegumes may be rhe"idcal crop for reducing capital and energy cxpenditures. Some tree iegumeshavc larse yields ofpods (19.20,2.1.22,23) and are droughr resistant (12. l9).Dala presented in this paper eslablish the facl that tree legumes produce largeamounts of high qual i ty prolein.

Trec legumes do nol require t i l lage, and some arc nodulated (24) wj lh reportedn i r r o g c n h r a t i o n r d l ( \ r a n g i n g t r o m 2 0 0 - 4 5 t g N p c r h a p e r y c a r r ? 5 r i o 5 8 0kg N per ha. pcr year (26). Woody tree legumes and shrubs comprise the bulk ofthe Mi ino\uiJca(. : r \ bldmrly .r f rhe LegumrnorJe. bur rrc ut.u fuun. l jn rhesubfamily Cacsalpinoideae. Whi lc only 10 percent of the Mimosoideae have beenexamined at the species level for nodulat ion. 87 pcrccnl of thosc examined arcrcported to be nodulated (24). Somc rropical rain fbresr soils wjth an eslimated50 perccnt leguminous lree cover h:rve soil organic maftcr conrents of l2 percent(27). Soi ls direcl ly beneath the crowns of lcguminous trees in Arizona (28), Senegal (29), Sudan (10), and India (31) have been shown ro have ni trosen and orsanicmattcr contents scverir l fo ld highcr rhan in the surroDndins soi ls. The soit underthe non leguminous t cc, llalanit?! dt gtpti../. had no such increase in nitrogenand organjc matter 110). This increase in thc ni l rogen and oryanic matler conrenr

A T T R I B U T E S O F A N I D E A L F O O D C R O P T R E g

Frc. L A lre€ lesumc showins cha.acleriilics desnrble for a milimal-cnefgy inDul asricullore.

is exceedingly important because the organic malter and nirrogen content ofthesesoils without leguminous lrees (0.3% ad 0.$q, respectively) is approximalelyl0-fold Iower than that found on temperate agricrltural soils. Some data suppo(the conclusion that soil nitrogen and organic marter may limil plant productiviryin semi-ar id cl inales even more than moisture avai labi l i ty (32,33), and this maybe the reason that leguminous lrccs occur on most of the dfy subtropicalforests which cover an area larger than Russia (14). I t is. indeed. unfortunatethat a study of ni t rogen-f ixat ion by leguminous trees in a narurat ecosysremo r t g l . u l l u r 0 l f i e l J . ( l t r n g h i r . n o t ] e t b c e n r e p o f r e d .

The ideal at tdbutes and the closeness wi lh which the mesquire tree (Ptusopis)approximaics these attributes are shown in Figure l. P/")rozir has palatable, low-tannin pods (Fig. 2) which have been used both fbr human and livestock food(9, 20. 35. 36, 37, 38, 19,40). Our experiments show there is 69 percenr prot€inin the seed after removal of the seed coat. Pft ,sopis (hi lcnsis also has a high seedto pod ral io. an importanl feature because rhe secd has more protein Der unir$ e r g h r r h c n l h e p o d . B u , . o n r 4 l r h a . r e p o r r e d a ! a l u e o f 1 5 0 m g m e r h i o n i n e g mof N in P'1)r.)p6 qfti(dna, an amounl which is several fold hisher rhan rharrequired by humans. Some authors (24.42.43) have reported nodulat ion in thegenus. The root system commonly extends 20 meters to the water rable (13) andoccasional ly lo the much greater depths of 60 and 80 meteN (13, 44).

The yield data of Figure I are close 1() the maximum pod yields measured forPn)sopi! tunkfftgo growing in regions where min falls only once every severalyears and where Ptusapis tunlarryo obtains its saline warer (0_ l%-0.3%) f'.om

l i l ' l . r . l : i t . t l r ' \ \ l r L l tSK r : | : r i l N l lN r ) t ; s IR I : l - s

b-toat

, ) '

l i . . l . Po f r i J :c . l dupho los ic r l ! r r i ib i l i \ "nxns .d ih lc t rcc l cgrm.s A t \ tLnr th t r t ) ta ,,trrkr (Airicrn li)cusr bcrn). pods $rrh 'ne{trlIcxn.scJ rnl\eel B I rrt nrt. lrrt t\ rlhdht lnttsln r l . c .1 . ( . f r l / r r . / / , , r t l , , J / / , . . p . , l \ rn l \ ceds D A, \ , ! , i \ ( / r t k r l / , \d lo re \q t r i rc ) r .ds nn{ lsco f : . L . .1 , r , r r , ! , r i l t , , , J i \ . p .n r anr l \ ce l \ | ( tn r , rn t r l i l r . (c r , .h ) . lod \ rn r l \ .eds GI 'nh t t r lLh i t l . , / r rn r t l9v Jer i r r ! ) . n .d ian i sce l \ H h t t tu ! r l l t tu r tuh , l )11 \ lh , r (J \ rh ) . soc ln^ l : - 1 ( ; l t t l i t \n t t tu t . r ! l ) ) t lh .d0 \ l . . t s l r . f . l \ xn( l s . . ( l r ' l h . sc r le i \ in ' r ch .s

a 6 o r dcer \ \ ra ic r tab le (23) . Cons ider ing ihc less than idea l cond i t ion ' j iD wh ich

Pto\or is taDtuntso Erows. a 10.000 krr /hr pod y ie ld goal is not unreasonrblc lbrothcr spccies . rnd selec l ions of / rd l i )p i r i fgrown in regions wi th groundwaler 'A South Al r ican rcpor t (45) est imates that / )?sa2i . r pod y ie l t ts of 9,000 ro l '1 .000ks/hr n ight conservat ive ly be expeclcc l in rcg ions o i 250 500 mm annual ra int 'a l l .

Mi l le t and pernut y ic lds in ScDcgal . Wcst Af f icr , rcceiv ing 600 mrn annur lru in in l are of the order d 1.000 kg/ha (46) . l f lesuminou\ t rces such as Pforo2i r ,!vh ich occu. nrruml ly in rcg ions of2-50 500 mm annual fa infa l l (45) . producc onlyonc scventh of rhc mc. l ian Pioro2i i /d , r . r r l r .qo pod y ie lds (7.000 kg/hn) (21) . thei rn ss y ie ld \vould st i l l equal those o l nr i l lc t and peanuls $ i lh the prcv iously dc-\cr ibcd rc lvantages of a no t i l lagc s! 's tem t fcc.

CO. l i \ r l ion r r tcs of 30 mg Co. /dnr ! /hr fbr P1)rd/ , ; . ! were measured in DealhVal ley. Cal i forn i l r . und arc: imong lhe h ighesl CO. f ixr t ion ratcs known tbf l reet(12) . These d l | t r r rdd crcdcncc to thc h ish pod y ic ld/ha data. fhe repor t thatPrordt l r has ! ssulaccan acid metabol ism ( l4) which : l lows i t lo c losc i ls sn)-n te! iD thc day and opcn lhcnr t t r n isht and. thus. 1() hel tcr k) ler t r lc dfouSht ( '17)

rcqui rcs conl i fmat ion. The lact thal / )1) ! i , / , i r is lo leranl lo l iost at '10"S. Lat . inAfgcnt ina (20) suggests the rangc to lvh ich i t miSht bc ac laplcd.

Thc t ime lo p ix l bear i rg in Pn)s. ) r i . \ has been repor lcd 1o bc as shor l as 20monrhs ( ,18) . thus a l lorv ing fbf rnpid select ioD for brccding. Simpson ( ,19) sLrsscsrsth: l t Pfd1, / ) l r l fu 'wcl . l are sel f - incompal ib lc and outcrossed by insech. I f such isthe casc, the heleruzygous sccds wi l l not rcsemble the parenl : rnd vegeta l iveprofasal ion lcchniques wi l l have 10 bc dcveloped. lh is outcrossing should fac i li ra lc l r . insf t r ( r f desimble !eDel ic chafrctcr is t ics betwecn t rccs, rnd. indeed. inlerspeci f ic hybr id izr l ion of Ptu\or is has beeD repor lcd to occur natuml ly ( l l )

Cont inuous l ish l ing has reduced the l ime re. tu i rcd for spfuce seedl ings 10 bc in

d , / e,)y l

t ' . tf , , : 'i L'ir

h

ncoNo\1tc BoIANY

TABLE I

Ess r r r ^ r ^MrNo ^ . rD DL r I

tC iN VAI - THR ILE LYS M E T cYs TRP

P(tkit . 1.tt1p(tuntnrxrt'

Pith.r (ll.hitnt sohnrar'

uri.nk<llnui\'P4sapi! \krhtnk"ur

Jtr,/,ru (seedsli!lilr4 lp.d.)"

L.t.t.nu l n...rhatu

no da ta ava i l ab l e

23

l8

l8

'Amino acidcomposilion ofthc lrichlo.oacetic acid p.ccipnable rlbudin d globrlin f.action iionsccd cmbryos. The Food and Asricultural Orsanizalion (FAO) provisional scores for adequacy inhuman nulririon in dC/gn N de: valine 2?0.lhreoninc 180. isoleucine 2?0. lysine 2?0, methionine1,14, cysline 126. and tryptophan $. Phenylalaninc. ryrosine. and leucine are not Iisted in this rableas thcy arc abovc lhc FAO provisiond score. The s€eds are graded wnh one x ror each 15% lheyfall below the score value. Thls ! x represenrs l0% bclow rhc rccommcndcd lalue and xxx rep-

' Seeds obbined irum the USDA No.lhcm Rc8lonal Research Laboralo.y. Peoria, tll.'Sccds obnined frcm Dr. Peter Mu.phy. Departmcnr of Borany and Planl Patholosy, Michisan

State Univcrsitv and collecled in Indonesia.' Seeds oblrined ltum Mr. Howard Hyland. USDA No.theastern Laboralory, Beltsvillc. Ma.yland,

frcm collecro( in Arsenrina.

the nursery befbrc outplanting from four years !o six months (50) and mieht nlsoprove us€ful in a tree legume breeding program.

We have chosen P/.,ropir as the example for our model since there is moreinformation or Prosopi.t than on other tree legumes.

SI ] I iD PROTF INS

We analyzed seeds from a number of leguminous trees for their protein andamino acid composition (51). The results of our suNey of the essential aminoacids of the seed proteins are presented in Table I. The amino acid compositionofthe proteins is compared with the Food and Agricultural Organization's (FAO)provisional scores for adequacy in human nutrition (52). Each x indicates theamino acid is l5 percent below the recommended value. FAO values for soybeanprotein are given for comparison. Our data on the amino acid composition ofPtosopis arc comparable ro those of Figueirdo (53), with the exception of thehydrophobic amino acids-a ditTerence which can be explain€d probably by theirmilder hydrolysis procedures. The amino acid composition ofthe Paltia spp. arealso in fair agreement with the work of Fetuga el al. (54) and Busson et al. (41).The amino acid composilion of the storage prolein of P. Iobat|n shows that itis of very high quality, having a chemical score (55) calculated from our data of

J .ELKLR. t BANI )T ]RSKI : I -FJCUMJNoUS I R I ]NS

0.79 compared 10 0.59 and 0.47 for casein and soy protein. respect ively. Unfbr-tunately. P. ldt trunt has seeds with the lowest protein content.

Almosl al l legume seeds re low in sul fur amino acids and in tryptophan. Ourdata. however. establ ish that there is considemble Senet ic diversi ty in proteinand amino acid composit ion of legume seeds, indicat ing that select ion for a seedhigh in protein and having a favorable amino acid profile is possible lt might alsobc possible to increasc lhc sul fur amino acid levels in the seeds with appl icat ionsof sulfare fertilizcr, since sulfate deilciencies have been reporled fbr lesumes onAl i ican savannah soi ls (56) and since sulfate def ic ient soi ls have been shown loreducc the propoft ions ol sul fur-r ich proteins in lcgume seeds (57). That theprotcin composit ion var ics from l6 Io 69 percent is encoufaging. because i t againindicates genet ic diversi ty. ()ur data on protein and amino acid composit ion rep-fesent only a f iacl ion of the species known. There are over 20 species ( 10, I I )ofP/ o.rd/rir from South America and several from North America (58) of which wehave analyzed only two. Considering that there are 90 varielies ofthe species ,.'r-c ua lucocepholt alone, lve can appreciate the apparcntly enormous genelicnotent ial (59).

I t must be mentioned that some legumes contain toxic substances. For instance,L.r / . ( . rd has mimosine in the Ieavcs. a depi latory when fed in excess to animals(60), and Pith4(llobiutn lab tunt (Djenkol bean) cluses hcmaturia when eatenin excess (61). Nonelhclcss, P. labat l t is regarded as a del icacy in lndonesia(6t), and Prkitl trli(oidra is repored to be toxin fiee (62).

The nutr i t ional qual i ty of mesquite pods for animal feed is adcqualely dem-onstrated by usase, but lhcre are difficulties. If Pr.,r.)pr:! pods are the sole foodsource fo. catt lc. approximately l% of the catt lc become sick, and some wi l l d iewi lh a compacted bal l of undigestcd mesquite pods in their rumen (63). Thislalal i ty has been attr ibuted to repression of rumen-bacter ial cel lulase act iv i ty bythe high susa. contcnt (107.) of the pods (63). Mcsquite feeding to non-ruminanls(pigs). whi le promising tbr the f i rst four wceks ofthe test pe od, was lcss pro-ducl ive during the fourth to tenth week of the fecding tr ia ls (64). and we suggestthat this may bc due to the presence of phylohemagglut inins and trypsin inhibi-lors, which have been recently dcmonslrated in nosotis /.rr.urlsd seeds (40).Such compounds are present in almost all legumes but cun be destroyed by heattreatment (65). ln conlrast, feeding tr ia ls with sheep. which have a greater abi l i ty10 break the h{d Prt,s|)pi! seeds than catlle, show a 15 percent hiSher proteindigeslibilily cocfficient for mesquite pods than alfhlfh hay (66).

USI iS OF TREF I E ( ;UMF:S

I f leguminous lrces are ideal crop plants, i t is legi t imale to ask why they arenot widely used as food sources in Europc and North America. The lower fie-qDency of leguminous trees prcsent in temperate veftus lropical regions partiallyaccounts for the lesscr use of t ree legumes in tempcratc regions. We hypothesizethat the lower frequcncy of t fee legume occurrence in tcmperate regions is ducto the slower organic matter degradation rate caused by lower temperaturcs (67),allowing organic mattel buildup and rcducing the selective advantage of nilrogen-fixation. We believe that the lack of active treelegume breeding programs is dueto the European or iain ofthe colonial ists, who had no basis for recognizing thevalue of t ree leguncs.

Pel issier (68), in considerins why A.d. i . r l l /b ldd was not bet ler dcveloped inWesl Africa. remarks (our translation fiom French).

One cannor heh bul bc asronished lhrl an dgroiomic rcscarch cenler established l,J nldv theSerer people (i. Sctrcsal. West Africr) il noi morc inlcrcsted nr the melhorls lnd cffcctilcncssof iativ. farmins syncms. These.ese2r.hers isnore lhe nrilieu ofnalLirally.eAencralins A. d, nl

shnds by which thcy arc surrounded. This mark of indifference and incomnrehention tbrAf.ican rcchniqucs is roo often m.nifen by European speciali\ls or those tfuined in Eunrpe.ln order ro pronoie lheir own culrunl vllucs, th.sc rcscarchcrs usc lhc tc.ms modcrn and'scientifi. .s if laborarory and ficld tcchniqucs arc completely inapplicable. fo. social o. eco-nonic rea$ns. Io th€ lrlly narive larmins systens. ,1((.tu d/rnl.r sull€s from the division ofrhe rechnicli *rvices. The aAronomisr rcsar{ls tie prescnce of th. lrcc in thc ncld as anftlv.narv b bc clinrinated. The fo.esrer is not inreresred rn rhe fee becaure Ai(rtr d/rir'(does not sftrw in rvhat could be rermed a ibresi and is, lhcrerbrc, nor capablc of bcin8 Jcaltwilh by srrndrd sylviculrure .oncerts. ric rolc of,4.d.r'zr z/rntr, includins ils s.owlh andgerdinarjon condnio.s. illust'ales ns marlcbus chnractcrs which cannot bc dissocialed fromirs scnuine agriculruml seuing and illurrates rhe necessily lor deen sealed ,crion 1o aid lhefarming nop0larion At rhis tifre in our inllmatc knowlcd8c ol polilical tcchniqucs for rumldrn.gedenr. o e.d must be piaccd lo lhc absurd division ofnsricuhuraliy related dhciplirreswhich encloses .griculruitl (levelopnenr specialjsls. h is nol a lack ol conccrn in lhc dcvcl-onmenr spccjllisls which causes rhis ptublcm bul nthcr thcn ovcHpccialized lminnrs. andahove all tlc adminlstrarivc srructu.cs which rhwa.r their action and hinder rn inleqrateddeleloDnrent Dlan lvhich alone can be efeclive.

The widespread usage of legum'nous trees for human and/or livestock food inthe subtropics and tropics is f i rmly establ ished. The lndians of the AmericanSouthwest and Mexico (35, 36,37,38,39. 69) and the Indians in South America(9. ?0) used P,osopis ̂s a human and l ivcstock food. Simi lar ly. Prrr l i . r is usedin the Afr ican savannah (41.62.711 and Pith(cl l ib i l tn loburrtn and Purkiur/r . . i r )s.r are nuch used in Malaysia (61, '72) as is Ptust,pis on the Indian sub-cont inent (34, 73, 74).

The geographical locat ions, uses, habitat , and yield of leguminous trees givenin Tabl€ I l indicate addit ional examples of their widespread use. They are em'ployed as food for humans or livestock in every major savannah in the world.For example, in Hawaii in 1910. Prosopis was regarded as the most valuableintroduced lree on the island (75) becausc of its use for livestock food. ln theNorth American Sonoran d€sert, ethnobotanists and anthropologists found thatPft,sdplr was the most important food of the Seri (69), Yuma and Mohave (37)Indians. ln Argentina. the center of diversity for the genus. Pf.)sdplr is widelyused as a food for humans and l ivestock as wel l as for f i rewood (9. 10. l l ) . InBrazil. where P,'or.)pis has been recently introduced, there has been considerablesludy of the chemicnl composit ion of the pods (51) with references to i ts use bylndians as a fbod source in pre-colonial Chi le, Peru, and Argent ina.

In South Africa. where Pi?s,rir anl Gl?litsid have been introduced, a Forestry Departmenl Bul let in l ists melhods ofcul t ivat ion, plant ins densit ies and yieldproject ions (45). This bul let in was produced at the request offarmers who d€siredinformalion on cultivation melhods fbr thcse fodder trees- There is also a sum-mary of a ten year UNESCO project on the cultivation of Pro.v?ir in south andeasrern Afr ica and in Indi (48). Yields of 20 tons of edible beans pcr hectare

In India. where P/17r.,pir is both narive and introduced (73), the leaves andpods are valued in arid areas as a livestock food. Species of Pllr(t:cllobirDt areI ikewise employed in India as fbrage (71).

In Mulaysia and Indonesia, scveral spccies of Prrrli.r and Pitfurtlhtbiutn ltbdrllr? are used as human food but rarely to fecd livestock (61, 72). No yield dataare available. and no attempt at developing these trees has taken place in Malaysiaand Indonesia. This is unfortunate because our data (51) show that isolated Pr,[.L?lbhiutn lobatrul protein has n higher total suli-ur amino acid content than ca-

The usc of leguminous trees in Africa as food for man and beast has beendocumented by Dalziel (62). l rv ine (71). and Busson (41). The senus P.r,*r .r(African locust bean) is the major tree legume producing human food in the

FELKER & BANDURSKI: LEOUMINOUS TREES

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savannah areas. Nutrirional studies done on a cultivar of a single species 154)indicate thal the seed is low in tryptophan and methionine. A fermented productfrom Purkiu, known as Soumbara or dawa-dawa, is eaten (76). A(u(iu alhi.la 1san important tree in Senegal and the Upper Volta, where the yields of milletgrown under the tree can be two and a half times higher than those from open-srown controls (29). Pods of AraLi( xlblzl.r are used to feed camel and cattle inthe dry season (30). Other leguminous trees of the African savannah with ediblepods arc Phsopis tJri(ana antl Penkkl?thra tliauophflll (41,62, 7l).

I1 is unfortunate that, $r'ith the exception of tbe data on a"r/../{,rd leaves. afodder in Hawaii (59). and the Chilean work on Ptusotlis tanatuso (23), ̂ ll orherinformation on yields are est imates. I t is encouraging, however, to note that,without correction for below-ground biomass, the C,r leguminous Iree Leu(aena(59) has a net annual primary productivity comparable to the highest reported(15) fbr any planl ecosystem and that an Indian savannah with unmanaged Pr'.)-r.276 receiving only 160 mrn of rain had a nel primary productivity of 14,500 kg/h a ( l 5 ) .

Sf ]MMARY

We have presented our concept of an id€al plant for reducing expendilures ofcapital, fossil f'uels, and machinery in agriculture of countries with limited re-sources. We further contend that, as fossil fuel sources are deplcted, these concepts may also be applicable to agricullures of affluent nations. We studied theprolein and amino acid composit ion ofthe seeds ofa number of leguminous treesfrom around the world, and this survey indicates a genetic diversity that makespossible the selection and breeding for specific seed proleins of desirable aminoacid composit ion. A br iefr€view ofthe uscs, y ic lds, aDd occurrence ofnodulal ionin the tree Iegumes has also been presented.

We feel that a research program should bc initiated to determine the actualIarge-scale and long-range yield of mesquite: to establish precisely, through feed-ing sludies. the nutr ient value of these seed proteins: to determjne the effect ofsulfate ferlilization on the sulfur amino acid content in the seed: and to determinethe suitability of tree legume syslems as crop plants in different parts of theworld. lmDroved varieties of P,1,r,r6 should be evaluated in the United Statesin areas of l ight f rost. Further north in the United States. Mi l lwood and Calhounvarieties of Cl?litsi( ttilt.mtlbs (21. 22) should be evaluated. The area of theworld where tree legumes would be most advantageous because of shortages ofindustrial inputs are the lndian Desert and Ganges Plain. the dry areas of Argen-t ina, Chi le and Pcru. and the sub Saharan savann.rh region.

Leguminous trees alone arc not thc answer to food problems in the semi aridtropics. ' Ihe solut ion resides in an integrated approach to populat ion control ,animal srazins. and waler al locat ion. to l ist but a few factors. However, legu-minous lrccs do play a role in food producl ion. and dnta presented here indicateahat lcguminous lrccs may offer a relut ively unexploi led potent ial .

The f inancial support of the Metrbol ic Biolosy Divis ion of the U.S. Nat ionalScience Foundat ion (Grant CB-40821-X and PCM 76 12356) is grateful ly acknowledged. We thank Dr. Peter Mufphy. Mr. Howard Hyland, and the slaff of thcNorlhcrn Regional Research Laboratory. Peoria, lllinois. for providing seed ma-terial, 1() Mr. Bruce Whiuker for the preparation of Figore l. and to BrendaGoucher and Rhonda Epstein for manuscript preparat ion.

F l l l ,KFR & BANDURSKI : LEGUMINOUS fREDs

r ITERAI 'URE CITDD

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