Ontogenetic Characteristics of Field Pea in a Semiarid Environment

Transcription

1 World Journl of Agriculturl Sciences (): 06-3, 005 ISSN IDOSI Pulictions, 005 Ontogenetic Chrcteristics of Field Pe in Semirid Environment Ynti Gn nd Pu-hi Liu Semirid Pririe Agriculturl Reserch Center, Agriculture nd Agri-Food Cnd, Swift Current, SK, S9H 3X, Cnd Deprtment of Wter Resources Engineering, Gnsu Agriculturl University, Lnzhou, Gnsu, , Chin Astrct: Identifying key yield components cn help estlish etter crop mngement strtegies to increse crop yield. The present reserch ws conducted in south-western Ssktchewn in 999 nd 000 to determine the interreltionships mong vrious yield components nd their direct nd indirect effects of ech component on seed yield of field pe (Pisum stivum L.). The semi-lefless cultivr Crrer ws plnted t the popultions of 35, 50, 65 nd 80 plnts m on conventionl summerfllow (CS) nd no-till whet stule (NT). The coefficients ( vlues) from pth nlyses reveled tht the seed yield of field pe depended primrily upon totl numer of pods per unit re ( =.4 for the pe on CS nd.39 on NT) nd secondrily upon seeds per pod ( = 0.59 for the pe on CS nd 0.44 on NT). The ssocition etween weight per seed nd yield ws either wek ( = 0.4 for the pe on CS) or negligile ( = 0.07 for the pe on NT). Among the vrious yield-relted vriles, totl numer of pods per unit re ws the gretest yield contriutor tht lrgely relied on plnts m ( =.35 for the pe on CS nd 0.97 on NT) nd on pods plnt ( = 0.78 for the pe on CS nd 0.74 on NT). Plnts m hd negtive, indirect effect through pods plnt, s did pods plnt through plnts m, ut those indirect effects were counterlnced y the direct effects of the components on totl pod production. Weight per seed ws highly nd positively relted to the length of reproductive growth. Seed yield in dry environment cn e incresed y incresing pod production, wheres weight per seed cn e improved y prolonging reproductive growth to increse the cotyledon cell size. Key words: Pisum stivum zero tillge summerfllow seed size plnt density INTRODUCTION of grin yield compred to NT conditions, wheres in wetter yers it seems tht CS-grown field pe produces Field pe (Pisum stivum L.) is one of the most similr grin yields s NT-grown field pe. importnt grin legumes in the world nd the grin is In commercil production of field pe, the cost of mjor source of plnt-sed dietry protein for nimls. seed is the mjor input expense, often exceeding US$50 This nnul legume is significnt contriutor to to $90 h, which ccounts for pproximtely ½ of the griculturl sustinility through N-fixtion nd s totl csh costs. Use of low seed rte cn potentilly rottion crop llowing the diversifiction of griculturl reduce the input expenditure, ut thin crop popultion production systems. Inclusion of this nitrogen fixer in usully results in severe weed prolems nd decreses cropping systems hs shown to improve nutrient nd seed yield [4]. In Western Cnd, field pe incresed wter use efficiency [], increse the yield nd qulity of the seed yield t rte of 5 kg h in wet yer nd susequent cerels nd oilseeds [] nd improve the 6 kg h in dry yer for every single plnt increse in economic sustinility of griculture [3]. In some regions plnt popultion from 35 to 80 plnts m. The increse of the world such s the semirid Northern Gret Plins of in seed yield is more pronounced for the CS-grown North Americ or Austrli, field pe is grown on either pe compred to the NT-grown pe. However, little is conventionl summerfllow (CS) or no-till (NT) cerel known out the interreltionships etween individul stule such s whet (Triticum estivum L) stule. In yield components nd the totl seed yield of field drier yers, field pe grown on CS performs etter in terms pe. It is unknown how pe plnts would djust their Corresponding Author: Dr. Ynti Gn, Semirid Pririe Agriculturl Reserch Center, Agriculture nd Agri-Food Cnd, Swift Current, SK, S9H 3X, Cnd 6

2 World J. Agric. Sci., (): 06-3, 005 ontogenetic chrcteristics to mximize seed yields under CS nd NT growing conditions. Informtion on the reltive importnce of vrious yield components to seed yields is useful for producers to mnge the crop y focusing on key yield components. This type of informtion lso is useful for reeders to improve selection criteri in genetic mnipultion. Selection for high yielding genotypes in nnul pulses requires knowledge on the mechnisms of seed formtion nd the physiologicl processes of pod forming [5] nd seed setting [6]. Pth coefficient nlysis, developed originlly y Wright [7] nd elorted y Dewey nd Lu [8] nd others, hs een used to determine the direct nd indirect effects of individul yield components on finl seed yields in nnul pulses such s dry en (Phseolus vulgris L.), soyen (Glycine mx L.) nd chickpe (Cicer rietinum L.) [6, 9, 0, ]. Pth nlysis lso hs een used to determine the interreltionships etween seed yields nd morphologicl chrcteristics in crops such s crested whetgrss (Agropyron desertorum F.) [8], spring whet [] nd spring rley (Hordeum vulgre L.) [3]. Pth coefficient nlyses usully prtition correltion coefficients into direct nd indirect effects of vrious yield components, sed on the ssumption of mutul reltionships mong yield components. Sttisticlly, pth coefficient is stndrdized prtil-regression coefficient, otined from equtions, where the yield-relted vriles re expressed s devitions from the mens in units of stndrd devition [4]. In these nlyses, seed yield nd yield components re regrded s system of interrelted vriles, with yield components considered t the sme ontogenetic level. The ojectives of present reserch were (I) to determine the reltive importnce of vrious yield components to finl seed yield of field pe grown under conventionl summerfllow nd no-till whet stule in semirid environment nd (ii) to ssess the reltionships mong seed yield, yield components nd the length of vegettive nd reproductive growth periods of field pe using pth coefficient nlysis. MATERIALS AND METHODS Field experiments were conducted in 999 nd 000 t two sites in southwestern Ssktchewn. The first site ws on n Orthic Brown Chernozem (Aridic Hploorolls) with lom to silt lom texture nd sturted-pste ph of 6.5 in the 0-5 cm depth [5]. This site ws t the Agriculture nd Agri-Food Cnd Semirid Pririe Tle : Seed nd seedling emergence of field pe (cv. Crrer) grown t four trget plnt popultion densities in southwest Ssktchewn, Cnd, Trget plnt popultion density (plnts m ) Pre-seed Seed weight germintion Yers (mg seed ) (%) Seedling emergence, % Agriculturl Reserch Center ner Swift Current (50. N, 07.4 W). The second site ws on Rego Brown Chernozem (Vertic Cryoorolls) with hevy cly texture nd sturted-pste ph of 6.8 in the 0-5 cm depth [5], on frmer s field ner Stewrt Vlley (50.6 N, 07.4 W). Experiment design nd plot mngement: A semi-lefless field pe cultivr Crrier with yellow cotyledons ws plnted t four seeding rtes to otin the trget Plnt Popultion Density (PPD) of 35, 50, 65 nd 80 plnts m (Tle ). The mount of seed used for the specific PPD trgets ws sed on seed size, pre-seed germintion nd n estimted field emergence rte of 75%. The vrious rtes of seeding were ccomplished with m wide hoe press drill equipped with spinner seed meter. The experiment ws rrnged in Rndomized Complete Block Design with four replictes. The sme set of tretments ws lyout oth on CS nd on NT; these two conditions were estlished side-y-side in the field, for ese of field opertions. The pe ws plnted t depth of 50 mm on 7 My 999 nd My 000 t Swift Current nd on 0 My 999 nd 5 My 000 t Stewrt Vlley, Ssktchewn, Cnd. At plnting, the noon soil temperture t 0 cm depth ws etween 9 nd 3 C. Ech plot ws 7.5 m long, consisting of 0 rows with 0 cm row spcing. Monommonium phosphte ws pplied in the seed rows t rte of 7.5 kg P h. All plots received n pproprite soil implnt Rhizoium inoculnt pplied to the seed rows. Weeds were controlled with ppropritely leled hericides to minimize the overll weed pressure. All plots were spryed with chlorothlonil t recommended rtes to control folir fungl diseses. Dt collection: After seedling emergence ws complete ( wk fter initil emergence), plnts were counted from two 0.5 m qudrnts per plot, one in the front of the plot nd the other in the ck of the plot. Phonologic stges of the crop were recorded sed on the Universl Growth Stging Scles [6]. Clendr dtes were recorded for seedling emergence (when 50% of the seedlings hd 7

3 World J. Agric. Sci., (): 06-3, 005 Tle : Person correltion coefficients for seed yield nd yield-relted vriles of field pe (cv. Crrer) grown on conventionl summerfllow (elow digonl) nd on no-till whet stule (ove digonl) in southwest Ssktchewn, Cnd, No-till whet stule Vegettive Pods Reproductive Pods Seeds Seed weight Seed yield Vriles Plnts m period plnt period m pod (mg seed ) (kg h ) Plnts m ** -0.63** ** Vegettive period * * -0.4* ** Pods plnt -0.7** * Reproductive period * ** 0.4** 0.8** -0.0 Pods m 0.78** ** -0.54* 0.97** Seeds pod -0.49* ** ** Seed weight (mg seed ) ** Seed yield (kg h ) 0.47** ** -0.4* 0.55** Conventionl summerfllow Tle 3: Pth coefficients for the seed yield (kg h ) of field pe (cv. Crrer) grown on conventionl summerfllow nd no-till whet stule in southwest Ssktchewn, Cnd, Conventionl No-till whet Pthwy summerfllow stule Multiple r Pods m vs seed yield Correltion (r 58) 0.90** 0.970** Direct effect (P 58).40**.390** seeds pod (r56p 68) seed weight (r57p 78) Seeds pod vs seed yield Correltion (r 68) -0.40* ** Direct effect (P 68) 0.590** 0.440** pods m (r56p 58) seed weight (r67p 78) Seed weight vs seed yield Correltion (r 78) 0.550** Direct effect (P 78) 0.40* pods m (r57p 58) seeds pod (r67p 68) The r nd P refer to pth coefficient nlysis of direct nd indirect effects mong yield components or vriles indicted y suscripts: = plnts m, = vegettive period, 3 = pods plnt, 4 = reproductive period, 5 = pods m, 6 = seeds pod, 7 = seed weight (g seed ) nd 8 = seed yield (kg h ), r 5 nd P 5 refer to correltion coefficient nd pth coefficient etween vrile nd 5, respectively. The sme definitions pply to the other coefficients, *, **, significnt t p 0.05 nd 0.0, respectively emerged in plot), nthesis (when 50% of the plnts in plot were looming) nd mturity (when seed moisture pproching 300 to 350 g kg ). At plnt mturity, we determined the verge numer of seeds per pod y rndomly smpling two, 50 pods from ech plot, with /3 of the pods tken from the ottom of the crop cnopy, /3 the middle nd /3 the top of the cnopy. The center eight rows of ech plot (9.7 m ) were comined with plot comine when the crop hd dried sufficiently for stisfctory threshing. The seed smples were ir-dried, clened nd weighed. Seed yield per unit re ws presented on dry weight sis. From the dried seed smple, we took susmples nd determined weight per seed sed on two, 500 individul seed smples. The numer of pods per plnt ws clculted using the plnt counts, seed weight nd seeds pod. Sttisticl nlysis: Dt were nlyzed using the PROC GLM nd PROC MIXED procedure of SAS [7], with lock nd site-yr s rndom effects nd PPD s fixed effect. A seprte nlysis ws performed for the two field conditions (CS nd NT). The PROC MIXED procedure tests the hypothesis concerning the fixed effects with correct error terms, ut it does not return significnt levels for rndom effects. The PROC GLM sttistics reveled no significnt site-yr y tretment interctions for most of the vriles mesured in the reserch. Therefore, the four site-yr dt were comined in the sttisticl nlysis. We first determined correltion coefficients mong yield components (Tle ) nd then we prtitioned the correltion coefficients into direct nd indirect effects using pth coefficient nlyses (Tles 3-5). The vriles used in these nlyses were () PPD, () the length of vegettive growth period (from seedling emergence to nthesis), (3) numer of pods per plnt, (4) the length of reproductive period (from nthesis to mturity), (5) numer of pods per unit re, (6) numer of seeds per pod, (7) weight per seed nd (8) seed yield per unit re. The cuse-effect systems used in the pth nlyses were sed on the ontogeny of field pe plnts (Fig. ). In this logistics, the numer of pods plnt nd the length of vegettive growth hve mutul reltionship, s oth chrcteristics my exercise reciprocl influence during the erly growth stges under norml conditions. The two growth periods (vegettive nd reproductive growth) were included in the logistics, 8

4 World J. Agric. Sci., (): 06-3, 005 Tle 4: Pth coefficients for pod production of field pe (cv. Crrer) grown on conventionl summerfllow nd on no-till whet stule in southwest Ssktchewn, Cnd, Conventionl No-till whet Pthwy summerfllow stule Multiple r Plnts m vs pods m Correltion (r 5) 0.780** 0.660** Direct effect (P 5).350** 0.970** pods plnt (r3p 35) Pods plnt vs pods m Correltion (r 35) Direct effect (P 35) 0.780** 0.740** plnts m (r3p 5) Tle 5: Pth coefficients for weight per seed (mg seed ) of field pe grown on conventionl summerfllow nd on no-till whet stule in southwest Ssktchewn, Cnd, Conventionl No-till whet Pthwy summerfllow stule Multiple r Pods plnt vs seed weight Correltion (r 37) Direct effect (P 37) reproductive period (r34p 47) seed pod- (r36p 67) Reproductive period vs seed weight Correltion (r 47) 0.580** 0.80** Direct effect (P 47) 0.490* 0.80** pods plnt (r34p 37) seeds pod (r46p 67) Seeds pod vs seed weight Correltion (r 67) Direct effect (P 67) pods plnt (r36p 37) reproductive period (r46p 47) The r nd P refer to pth coefficient nlysis of direct nd indirect effects mong yield components or vriles indicted y suscripts: = plnts m, = vegettive period, 3 = pods plnt, 4 = reproductive period, 5 = pods m, 6 = seeds pod, 7 = seed weight (g seed ) nd 8 = seed yield (kg h ), r 37 nd P 37 refer to correltion coefficient nd pth coefficient etween vrile 3 nd 7, respectively. The sme definitions pply to the other coefficients, *, **, significnt t p 0.05 nd 0.0, respectively sed on previous findings [8] tht prolonged period of reproductive growth llowed nnul pulses to ccumulte more het units tht enefit pod setting nd seed formtion. In the present reserch, the period from seedling emergence to nthesis verged 4d nd from nthesis to mturity 3d for field pe. During the reproductive growth period, new pods were continuously formed, while the pods formed t the erly-podding stge were in seed-filling process. Therefore, the length of Plnt density () Vegittive period () Pods plnt (3) Reproductive period (4) Pods m (5) Seeds pod (6) Seeds weight (7) Seed yield (8) Fig. : Pthwys showing the cuse-effect reltionships mong yield components nd their effects on seed yield of field pe grown in the semirid environment of southwestern Ssktchewn, Cnd, reproductive period my hve modified pods plnt nd seeds pod. The numer of pods per unit re my directly influence yield components tht were formed in the lter prt of the development stges. Finlly, seed weight depended on the durtion of the reproductive period, pods plnt nd seeds pod. The pth coefficient nlysis, similr to those used y other reserchers [6, 3], ws used to prtition the correltion coefficients mong yield-relted vriles into direct nd indirect effects y solving the following sets of equtions simultneously: r 58 = P 58 + r56p 68 + r57p78 r 68 = r56p 58 + P 68 + r67p78 r 78 = r57p 58 + r67p 68 + P78 r 37 = r43p 47 + P 37 + r36p67 r 47 = P 47 + r43p 37 + r46p67 r 67 = r46p 47 + r36p 37 + P67 r = P + r P r = r P + P r = P + r P + r P + r P r = r P + P + r P + r P r = r P + r P + P r = r P + r P + P r = P + r P r = r P + P r = r P + P r = P + r P In the eqution of r 5 = P 5 + r3p 35, r 5 is the correltion coefficient etween vrile (plnt density in Fig. ) nd vrile 5 (pods m in Fig. ), the P 5 is the pth coefficient for the direct effect of vrile on 9

5 World J. Agric. Sci., (): 06-3, 005 vrile 5 nd r3p 35 is the indirect effect of vrile on seeds pod positively ffected seed yield in oth vrile 5 vi vrile 3 (pods plnt in Fig. ). Similr growing environments, while this effect ws not shown in definitions pply to the rest of the equtions. Test for the correltion nlyses, where such n effect ws significnce of pth coefficients ws chieved y testing proly overshdowed y indirect effect of pods m for prtil regression coefficient. (r56p 58 = -.03 to -. in Tle 3). Conversely, the correltion nlysis reveled strong ssocition RESULTS AND DISCUSSION etween weight per seed nd seed yield for the pe grown on CS, ut this effect ws counterlnced y Growing seson (My through August) the negtive effect of weight per seed on seed yield precipittion ws 50 mm in oth study-yers, 5% greter through pods m. As result, there ws only slight thn the 40 yr (96-000) verges, wheres the men ir direct effect of weigh per seed on seed yields tempertures (5. C) were close to the long-term (pth coefficient = 0.4) only when the crop ws grown verges. The fvorle moisture conditions in the erly on CS. Most of the indirect effects of yield components spring llowed good seedling estlishment, with the on seed yield were wek (Tle 3), except the indirect verge seedling emergence >9% in oth yers (Tle ). effect of seeds pod on seed yield vi pods m ws The ctul plnt density ws close to the trgets t ll high, which ws proly due to gret direct effect of levels (i.e., from 35 to 80 plnts m ) designed in the pods m on seed yield. Previous studies found no direct experiment. The wide rnge of PPD provided n excellent effect of weight per seed on seed yield in chickpe [], opportunity to exmine the interreltionship mong yield though those two trits were highly correlted in components of field pe grown under oth CS nd NT correltion nlysis. In soyen, weight per seed hd no conditions. phenotypic effect on seed yield [6, 0]. However, weight per seed expressed genetic correltion with seed yields Seed yield: Results of the effects of PPD on seed yields when different genotypes were compred in tests. hve een reported elsewhere [8]. In rief, seed yields incresed with incresing PPD from 35 to 80 plnts m Pod production: Totl numer of pods per unit re regrdless of growing conditions. Yield increses with functioned s mjor contriutor to seed yields of field incresing PPD were more pronounced for the pe grown pe under oth CS nd NT conditions (Tle nd 3). on CS compred to when grown on NT. Greter soil This vrile ws product of plnts m nd pods moisture in the CS field promoted more fertile pod plnt, thus it is worthwhile to exmine the reltive production under the semirid conditions. Person mgnitude of these two components. Pth coefficients correltion nlyses reveled tht the seed yield of field reveled tht totl pods minly depended on plnts m pe highly nd positively depended on pods m nd nd secondly on pods plnt (Tle 4). The growing plnts m nd ws negtively correlted with seeds environment did not lter these ssocitions, lthough pod (Tle ). Similr types of correltion existed for the field pe grown on CS hd stronger reltionship (pth pe grown on CS (coefficients elow digonl) s those coefficient =.35) etween plnts m nd totl pods grown on NT (coefficients ove digonl). The only compred to when the crop ws grown on NT (pth difference ws tht the seed yield ws positively ffected coefficient = 0.97). Liner regressions strongly y weight per seed when the pe ws grown on CS, while supported these oservtions (Fig. ) where the totl it ws positively ffected y the period of vegettive numer of pods incresed significntly s PPD incresed. growth when the crop ws grown on NT. The slope of the liner regression ws greter for the Pth coefficient nlyses provided more insights pe grown on CS compred to NT. There ws negtive on the interreltionship mong yield components nd indirect effect of plnts m on totl pod production their effects on seed yields, ecuse pth coefficients through pods plnt (r3p 35 = -0.3 to -0.57) (Tle 4). prtitioned correltion coefficients into direct nd This negtive reltionship ws due to the fct tht indirect effects. The direct effects of pth coefficients incresing PPD significntly reduced numer of pods per (Tle 3) reveled tht the seed yield of field pe plnt (Fig. ). However, such negtive effect of pods depended primrily upon pods m nd secondrily plnt on totl pod production ws counterlnced y upon seeds pod, with the direct effect of weight per the strong, direct effect of plnts m (Tle 4). In seed on seed yield eing either slight ( = 0.4, p < 0.05, ddition, pth coefficient reveled negtive, indirect for the pe grown on CS) or negligile ( = 0.07, p = 0.3, effect of pods plnt on totl pod production through for the pe grown on NT). Pth coefficients showed tht plnts m (r P = to in Tle 4). Agin, the 3 5 0

6 World J. Agric. Sci., (): 06-3, 005 correltion nlyses. In the present reserch, the numer of pods produced on ech plnt decresed from 0 to 4 s PPD incresed from 35 to 80 plnts m under oth CS nd NT conditions (Fig. ). Nevertheless, the pods plnt cted s fctor, second to plnts m, significntly influencing totl pod production in field pe. These results indicte tht incresing plnt popultion density is the key to produce sufficient numer of pods for mximizing seed yield of field pe in the semirid environment. In ddition, the numer of pods incresed significntly with prolonging vegettive growth, when the pe ws grown on NT (Tle ). However, the increse of pod production cused reduction in the numer of seeds per pod. In comprison, when the pe ws grown on summer fllow, totl pod production ws independent of the length of vegettive growth period or the numer of seed per pod. We did not determine these reltionships with pth coefficient nlyses ecuse we elieve tht totl pod production is function of the comintion etween plnts m nd pods plnt. The influence of the vegettive growth period on pod production is reflected directly through pods plnt with the cusl-effect reltionship tken into considertion. These results indicte tht totl pod production ws the gretest fctor contriuting the finl seed yield in field pe. Pod production potentil cn e incresed through djusting seeding rtes for higher trget plnt popultion nd y promoting more pods on per plnt se. Incresing plnt popultion density reduced the numer of seed per pod (Fig. c), ut this reduction could e prtly counterlnced y incresed totl numer of pods per unit re (Fig. ). Our findings on the effect of pod production on seed yield gree with those found in other nnul pulse crops, including kuli chickpe [, 9], desi chickpe [0], f en [], soyen [6] nd lentil (Lens culinris Medik.) []. Fig. : The effects of plnt popultion density on pod Weight per seed: Weight per seed ws lrgely dependent production nd seeds per pod for field pe on the length of reproductive period nd ws unrelted to (cv. Crrer) grown t southwestern fctors such s pods plnt or seeds pod (Tle 5). Ssktchewn, Cnd, Similr responses of weight per seed to reproductive growth were oserved for the field pe grown on CS nd strong, direct effect of pods plnt overshdowed the NT, lthough the response ws greter for the NT-grown negtive nd indirect effect. Correltion etween field pe compred to CS. Reson for the different pods plnt nd totl pod production ws not responses on CS versus NT field pe is unknown, ut we significnt, ut pth coefficient showed highly speculte tht the reproductive growth my influence the significnt direct effect. It ws possile tht the negtive, mitotic rte during the cell division phse to chieve indirect effect of pods plnt on totl pod production differences in cell numer found in the cotyledons. The through plnts m my hve msked the positive, direct endoredupliction level in mturing cotyledons might e effect of pods plnt on totl pod production in the closely relted to the volume of cotyledon cells. An

7 World J. Agric. Sci., (): 06-3, 005 incresed numer of endoreduplicting cycles in the pe plnts to tke dvntge of residul soil wter for cotyledons with prolonging reproductive growth period rpid cnopy development, erly flowering nd lengthen might hypotheticlly increse the cotyledon cell size. In the period of reproductive growth for mximum seed previous reserch, Gn et l. [8] found tht field pe setting. plnted t n erly dte ccumulted more het units during the reproductive period nd produced higher seed ACKNOWLEDGEMENTS yields with greter weight per seed thn the pe plnted t lter plnting dte. Pe seed weight ws closely We cknowledge the excellent technicl ssistnce relted to the reproductive nodes on the min stem nd of Clvin McDonld, Lee Poppy, Greg Ford nd Ry rnches under the dry conditions of Austrli [3]. The Leshures nd the finncil support of Ssktchewn cultivrs tht flower t n erlier dte produce more Pulse Growers, the Agriculturl Development Fund of reproductive nodes thn did the lter flowering cultivrs. Ssktchewn Agriculture nd Food nd the Mtching Individul seed mss of pe lrgely depends on the Investment Inititive of Agriculture nd Agri-Food sequentil processes of reproductive development [4]. Cnd. We lso grtefully cknowledge Dr. Crig Time intervls etween the initition of flowering nd Stevenson for conducting sttisticl nlyses nd physiologicl mturity vries widely with growing Dr. Dve McAndrew (Morden, AAFC) nd Dr. M.S. Adk conditions. Field pe plnts grown t high plnt densities (Ankr University, Turkey) for reviewing the mnuscript. re normlly under conditions of higher plnt-to-plnt competition nd hve lower rte of progression in REFERENCES flowering nd seed filling thn plnts grown under lower competition conditions.. Miller, P.R., B.G. McConkey, G.W. Clyton, S.A. Brndt, J.A. Strick, A.M. Johnston, G. Lfond, CONCLUSIONS B.G. Schtz, D.D. Bltensperger nd K. Neill, 00. Pulse crop dpttion in the northern Gret Plins. Present reserch determined the interreltionships Agron. J. 94: 6-7. mong seed yield nd yield components of field pe using. Gn, Y., P.R. Miller, B.G. McConkey, P.R. Zentner, pth coefficient nlyses. The results indicte tht the F.C. Stevenson nd C.L. McDonld, 003. Influence some of the yield components were interrelted in of Diverse Cropping Sequences on Durum Whet different mnner in pth nlysis thn those shown in Yield nd Protein in the Semirid Northern Gret correltion nlysis. Correltion nlysis identifies Plins. Agron. J., 95: mutul ssocitions mong the vriles of interest, 3. Zentner, R.P., C.A. Cmpell, V.O. Biedereck, P.R. wheres pth coefficient nlysis determines the reltive Miller, F. Selles nd M.R. Fernndez, 00. Serch mgnitude of the effect for ech vrile. Pth coefficient of sustinle cropping system for the semirid nlyses serve s more useful tool thn simple Cndin priries. J. Sustinle. Agric., 8: correltion nlyses when the im is to identify the direct 4. Gn, Y., P.R. Miller, B.G. McConkey, R.P. Zentner, nd indirect effects of vrious components tht hve P.H. Liu nd C.L. McDonld, 003. Optimum plnt cuse-effect reltionships. Present reserch shows tht popultion density for chickpe nd dry pe in the numer of pods per unit re is the foremost importnt semirid environment. Cn. J. Plnt Sci., 83: -9. yield contriutor in field pe nd tht trgeting higher 5. Bord, J.E. nd Q. Tn, 995. Assimiltory cpcity plnt popultion density to increse pod production effects on soyen yield components nd pod is the key to increse seed yield of field pe in dry numer. Crop Sci., 35 : environments. Prolonging the period of reproductive 6. Bll, R.A., R.W. McNew, E.D. Vories, T.C. Keisling growth increses weight per seed nd seed yield nd L.C. Purcell, 00. Pth nlyses of popultion significntly. Promotion of erlier flowering cn e used density effects on short-seson soyen yield. s strtegy to increse the numer of seeds per pod Agron. J., 93: nd to enhnce weight per seed for field pe in dry 7. Wright, S., 9. Correltion nd custion. J. Agric. environments. Pe plnts fvor cool conditions during the Res. (Wshington, D.C.) 0: erly growth stges. In the northern Hemisphere, the 8. Dewey, D.R. nd K.H. Lu, 959. A correltion nd field pe could e seeded s the first crop in spring once pth-coefficient nlysis of components of crested the seeded moisture is permitted. Erly seeding llows whetgrss seed productio Agron. J., 5:

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