COMPETITIVITY OF THE COMMON-BEAN PLANT RELATIVE TO THE WEED ALEXANDERGRASS [Brachiaria plantaginea (Link) Hitch.]

Transcription

1 Competitivity of the ommon-en to B. plntgine 59 COMPETITIVITY OF THE COMMO-BEA PLAT RELATIVE TO THE WEED ALEXADERGRASS [Brhiri plntgine (Link Hith.] Telm Pssini,4 ; Pedro Jo Christoffoleti,4 *; Inês Fumiko Uukt Yd 3,4 IAPAR, Áre de Fitoteni, C.P Londrin, PR - Brsil. USP/ESALQ - Depto. de Produção Vegetl, C.P Piri, SP - Brsil. 3 IAPAR, Áre de Biometri, C.P Londrin, PR - Brsil. 4 CPq sholr. *Corresponding uthor <pjhrist@eslq.usp.r> ABSTRACT: Methodologies of ompetitive intertion quntifition eteen eeds nd rops re not idely eluidted nd ompred in the literture. The ompetitive ility of ommon-en (Phseolus vulgris reltive to lexndergrss (Brhiri plntgine s ssessed nd to pprohes of replement series experiment nlysis ere ompred. The response of the speies to the presene of eh other t different densities nd proportion s evluted. Replement series t totl densities of 65, 86 nd, plnts m - ere performed t the proportions of ommon-en:lexndergrss of : (pure stnd of ommon-en, 75:5, 5:5, 5:75 nd :% (pure stnd of lexndergrss, t four replites in rndomized lok design. Dt nlyses ere performed y the qulittive ompred to the quntittive pproh. The quntittive pproh provided lrger numer of informtion thn did the qulittive pproh, nd indited tht there s intrspeifi ompetition mong ommon-en plnts, nd minimum of interspeifi ompetition from lexndergrss. There s no intrspeifi ompetition mong lexndergrss plnts, eing the rop effet on the eed lrger thn the effet mong lexndergrss plnts. The eologil nihe differentition s prtil, sine the rop intrspeifi ompetition s lrger thn the interspeifi, nd the lst one s negligile, t the sme time tht the eed interspeifi ompetition s lrger thn the intrspeifi. Common-en, s ompetitor speies, is superior to lexndergrss. Key ords: replement series design, qulittive nlysis, quntittive nlysis COMPETITIVIDADE DO FEIJOEIRO-COMUM COM O CAPIM-MARMELADA [Brhiri plntgine (Link Hith.] RESUMO: As metodologis de quntifição ds interções ompetitivs entre plnts ultivds e dninhs não estão mplmente eluidds e omprds n litertur. A ompetitividde d ultur de feijão-omum (Phseolus vulgris em relção o pim-mrmeld (Brhiri plntgine foi vlid pel omprção entre o método qulittivo e um método quntittivo de nálise de resultdos. A respost de d espéie à presenç d outr foi otid em três séries sustitutivs ns densiddes totis de 65, 86 e. plnts m -. Em d série, s proporções entre plnts de feijão-omum e de pim-mrmeld form de : (estnde puro de feijão-omum, 75:5, 5:5, 5:75 e :% (estnde puro de pim-mrmeld. Os trtmentos form dispostos em delinemento experimentl de loos o so, om qutro repetições. O método quntittivo proporionou mior número de informções que o qulittivo e evideniou que pr o feijãoomum houve ompetição intr-espeífi e mínim ompetição interespeífi do pim-mrmeld. ão houve ompetição entre s plnts de pim-mrmeld, sendo que, o efeito d ultur sore plnt dninh foi mior que o efeito ompetitivo entre s plnts de pim-mrmeld. A diferenição de niho eológio foi pril um vez que ompetição intr-espeífi d ultur foi mior que interespeífi, sendo últim desprezível, o mesmo tempo que ompetição interespeífi sore plnt dninh foi mior que intr-espeífi. O feijão-omum, omo espéie ompetidor, é superior o pim-mrmeld. Plvrs-hve: séries sustitutivs, nálise qulittiv, nálise quntittiv ITRODUCTIO Methodologies of ompetitive intertion quntifition eteen rops nd eeds re not idely eluidted nd ompred in the literture. Hrper (977, Oliver & Buhnn (986, nd Rejmánek et l. (989 desried tretment designs for ompetition studies nd Oliver & Buhnn (986 desried their dvntges nd disdvntges. Lter on, Cousens (99 nlyzed the ritiques tht some designs hve reeived nd onluded tht even the simplest one is pproprite to the ojetives of ertin studies. Among the ville de- Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3

2 6 Pssini et l. signs to e used in ompetition studies, uthors hve mentioned the dditive, replement series, systemti nd surfe response designs. The replement series hve een used minly to determine the est ompetitor of to speies or iotypes nd to understnd ho they intert to eh other (Cousens, 99. In this kind of design, the totl density is held onstnt hile the proportion eteen the to speies is vrile (Hrper, 977. Tretments re estlished from pure stnd of one speies nd plnts re progressively repled ith plnts of seond speies up to pure stnd of the lter one (Spitters, 983. Besides the pure stnd of eh speies, t the sme density, tretment ith the proportion of : is frequently used (Connoly, 988. The totl density must e t lest enough to stisfy the onstnt finl yield l, i.e., the totl density of plnts hih ptures ll ville environmentl resoures. At this ondition, the totl iomss yield is onstnt, even if there is n inrement in the numer of plnts per unit re (Wit, ited y Roush et l., 989. The interprettion of the results of n experiment onduted s replement series n e done y the onventionl pproh, qulittively, nd quntittively, using mthemtil equtions. The qulittive interprettion is performed y ompring oserved nd expeted yields, ith the ltter eing liner funtion of speies proportions in the mixture. The stright line tht onnets eh speies yield in the pure stnd (: to its zero yield (: defines the expeted yield, hih is onsidered to represent the ompetitive equivlene response (CE in hih the intrspeifi ompetition is equivlent to interspeifi ompetition (Rejmánek et l., 989. The quntittive interprettion of results from replement series experiment strted y the end of the 95's hen liner reltion eteen the reiprol yield per plnt nd the plnt density s empirilly determined (Kir et l., ited y Rejmánek et l., 989. This reltion s determined for one speies, nd lter on tht s expnded to to-speies mix to otin pir of liner equtions (Og, ited y Rejmánek et l., 989. Other sientists, using the sme priniple, developed pir of orresponding equtions (Spitters, 983; Jolliffe et l., 984. Compring the reiprol yield per plnt method of Spitters (983 to the doule reiprol yield method of Jolliffe et l. (984, Roush et l. (989 onluded tht the first s simpler ith regrd to the mesurement of the reltive importne of the intr- nd interspeifi ompetition nd more sensile to mesuring the intertion eteen density nd proportion of the speies mixture. As lexndergrss is n importnt eed in ommonen rop, the ompetitiveness of these speies s evluted y ompring the qulittive to the quntittive pproh to dt nlysis. MATERIAL AD METHODS To experiments ere onduted in greenhouse, in Piri, SP, Brzil. In the first, the plnt density ( - plnts m - to eh speies (ommon-en nd lexndergrss in hih the yield of shoot iomss per unit re (Y - g m - eomes independent of the density s determined, ording to the onstnt finl yield l. From the results of this experiment, seond experiment s set to determine the ompetitiveness of oth speies. The greenhouse temperture s regulted to mximum of 5 C nd the irrigtion s done y sprinkling, every to hours, from 7h to 7h, pplying every dy totl of mm of ter. In loudy or riny dys the irrigtion s done from 9h to 5h. Seeds of ommon-en (Phseolus vulgris L. nd lexndergrss [Brhiri plntgine (Link Hith.] ere ommerilly quired. The seeds of the Crio ommon-en vriety, ith 8% germintion nd 98% purity, ere treted ith roxin + thirn. Alexndergrss seeds shoed, in the germintion test, tht the first plnts emerged t the sixth dy fter seeding, nd the emergene rte s 5 seedlings per.58 g of seed. Plsti pots (8.5 m upper dimeter, 4. m loer dimeter, nd 5. m height ere filled ith mixed sustrte mde up of soil mteril, snd, rotten mnure, nd ronized rie husk (3:::.5 volume proportions, nd treted ith methyl romide to redue the eeds. The numer of plnts of eh speies per pot s reorded t the hrvest time. Shoots ere ut off t the soil level, dried t 75 o C for 48 hours nd eighed. Density in hih the speies rehes the onstnt finl yield Experiments ere rried out in rndomized lok design ith four replites. Common-en nd lexndergrss ere studied seprtely t densities of,, 4, 8, 6, 3 nd 64 plnts per pot, hih orrespond to 37, 74, 49, 97, 595,,9 nd,38 plnts m -. The popultion of 4 plnts of ommon-en per pot (89 plnts m - s lso studied. Pots ere filled ith the sustrte up to.5 m elo the top of the order of the pot. Common-en seeds ere distriuted on the surfe of the sustrte nd overed ith portion of the sustrte up to the top of the order of the pot. Alexndergrss seeds nd portion enough of the sustrte to omplete the volume of eh pot ere mnully mixed in plsti g. Exess seeds ere son (/4/999 nd plnts ere thinned tie (//999 nd //999 to the required densities. The finl stnd s reorded nd shoots ere hrvested dys fter seeding (/3/. At tht time, ommon-en plnts ere t the V3 stge (CIAT, 983, nd the lexndergrss, t the 4 stge (Zdoks et l., 974. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3

3 Competitivity of the ommon-en to B. plntgine 6 Dry iomss yielded per unit re (Y nd density ( ere used to lulte the reiprol of dry iomss yielded per plnt (/ = /Y. These dt ere used to perform liner regression nlysis ith / s the dependent vrile nd s the independent vrile. The otined oeffiients ere used to rite the eqution (eq. of the reiprol of shoot dry iomss yield per plnt (Spitters, 983: = o + ( nd the eqution (eq. of the totl of dry iomss yielded: Y = o + ( here, represents the reiprol of the iomss of n isolted plnt; represents the rte of inrese in / or the rte of derese in relted to the ddition of eh plnt to the popultion, nd it lso is the reiprol of the mximum iomss per unit re ( =/Y mx hen density ( tends to infinity; nd / expresses the inrese of / reltive to its vlue in the sene of ompetition nd, therefore, it mesures the intrspeifi ompetitive stress (Spitters, 983. One the dt ere djusted to the hyperoli eqution (eq., the minimum vlue of density in hih Y ould e similr to Y mx s determined for eh speies. The differenes mong the oserved Y vlues nd the vlue of Y mx ere lulted for eh density. The null hypothesis (H s tht the verge of eh of these differenes s equl to zero. To test the H, it s verified if the vlues of the differenes present norml distriution (W-test. Presenting norml distriution [(Pr<W>.5], the omprison s done y t-test, epting H hen [(Pr> T >.5]. Determintion of the ompetitiveness of ommon-en reltive to lexndergrss Tretments ere set in three replement series of four replites in rndomized lok design. The totl density of eh replement series s 65, 86 nd, plnts m -. In eh series, the proportions of ommon-en to lexndergrss plnts ere : (pure stnd of ommon-en, 75:5, 5:5, 5:75 nd :% (pure stnd of lexndergrss. The desired densities ere simulted y keeping 6 plnts per pot in the sping of 4. x 4. m (65 plnts m -, 3.5 x 3.5 m (86 plnts m - nd 3. x 3. m (, plnts m -. These plnt sping ere otined y using grids mde of ood to filitte the orret plement of the seeds in the desired density t equidistnt points (Figure. At son (/3/, to seeds of ommonen nd rndom mount of lexndergrss seeds ere pled t eh pre determined spot (Figure. To thinnings (/5/ nd /7/ ere mde to estlish the desired densities in eh tretment. At dys fter seeding (//, the numer of plnts s reorded, nd the shoot of eh speies s seprtely hrvested to determine the dry iomss. The ommon-en plnts ere hrvested t the V3 stge (CIAT, 983 nd the lexndergrss plnts t the 4 stge (Zdoks et l., 974. The results ere nlyzed qulittively or onventionlly (Hrper, 977, nd quntittively (Spitters, 983. Qulittive nlysis of the speies ompetitiveness The qulittive nlysis s performed for eh replement series nd for the verge of the three replement series y visul interprettion of the reltive yield s funtion of the to speies proportions. Reltive yields (Yr of one speies ere lulted s dry iomss yield of tht speies (Yx t eh proportion divided y the yield from the tretment ith % of plnts of the sme speies (Y (Roush et l., 989: Yx Yr = (3 Y Liner nd qudrti regression nlyses ere performed ith the reltive yield (verge of four replitions s the dependent vrile nd density proportions s independent vriles. Eh of lulted reltive yield (Yr s ompred to its orrespondent vlue on the ompetitive equivlene line (Y CE. For eh speies, the vlues on the ompetitive equivlene line t the proportions of, 5, 5, 75 nd % (X xis ere, respetively of ;.5;.5;.75 nd.. XXXX XXXX XXXX XXXX XXXO XOXX XXXO XOXX OXOX XOXO OXOX XOXO OOOX OXOO OOOX OXOO OOOO OOOO OOOO OOOO = 6 = = = 4 = 8 = = 6 Figure - Arrngement of plnts in the pots for the totl density of 65 plnts m - (6 plnts per pot t the sping of 4. x 4. m. For densities of 86 nd, plnts m -, the sme plnt rrngement s used, ut reduing the sping. ( numer of plnts, rop, nd - eed. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3 = 8 = 4 =

4 6 Pssini et l. The null hypothesis (H s tht differenes mong the mens of Yr nd Y CE ere similr to zero. To test H, it s verified t first if the vlues of the differenes folloed the norml distriution (W-test. Shoing norml distriution [(Pr<W>.5], the omprison s mde ith the t-test, epting H hen [Pr> T >.5]. Quntittive nlysis of the speies ompetitiveness Dry iomss yielded y the rop (Y nd the eed (Y, nd plnt densities ( nd ere used to lulte the dry iomss yielded per rop plnt ( = Y / nd per eed plnt ( = Y /. The reiprol yield per plnt (/ nd / ere sumitted to multiple liner regression nlysis, ith nd s dependent vriles, exluding those three tretments in hih the speies representing the dependent vrile s sent, s proposed y Rejmánek et l. (989. The otined oeffiients ere used to rite pir of equtions, s proposed y Spitters (983: =, o +, +,, =, o +, +,, (4 (5 The first susript of eh term refers to the speies hih iomss is eing onsidered, hile the seond susript identifies the ssoited speies. The oeffiients for intrspeifi (, nd, nd interspeifi (, nd, ompetition ere used to lulte the reltive ompetitive ility (RC of ommonen nd lexndergrss (eq.6 nd eq.7, s ell s the eologil nihe differentition index (DI eq.8, ording to Spitters, (983: RC RC, = (6,, = (7, DI = RC RC (8 There is nihe differentition hen DI exeeds unity (Spitters, 983. RESULTS AD DISCUSSIO Density tht leds to onstnt finl yield for eh speies The oeffiients from the liner regression (Tle, ere used to rite the equtions s the eq. ( (Figure.A ommon-en nd Figure 3.A - lexndergrss. Considering the iologil mening of the oeffiients (Spitters, 983, the theoretil mximum yield of the dry eight (Y mx of ommon-en shoot s g m - (/ = /.43 = (Figure.B nd the lexndergrss, 7.64 g m - (/ = /.8535 = 7.64 (Figure 3.B. For eh ommon-en plnt dded to the popultion, the reiprol of the dry iomss per plnt (/, hs inresed, or the dry iomss per plnt (, s redued y.43 g (. In the sme y, for eh lexndergrss plnt dded to the popultion, the reiprol of the dry iomss per plnt (/, hs inresed, or the dry iomss per plnt (, s redued y.8535 g. The redution in the dry iomss yielded per plnt hen one plnt s dded to the popultion s smller for the ommon-en, inditing tht this speies, ompred to lexndergrss, presented loer intrspeifi ompetition. This ft s onfirmed y the intrspeifi index of eh speies, lulted y the rtio /, hih expresses the inrese in / reltive to its P. vulgris - / (plnt g - P. vulgris - Y (g m A P. vulgris - (plnts m B =, ,43 x, r =,8 Y máx = 958,778 g m - Y = (, ,43 x P. vulgris - (plnts m - Figure - A - Effet of the density of P. vulgris ( on the reiprol of dry iomss yielded per plnt (/. B Effet of the density of P. vulgris ( on dry iomss yielded per re (Y. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3

5 Competitivity of the ommon-en to B. plntgine 63 vlue in the sene of ompetition, nd n e used s mesurement of the intrspeifi ompetition stress (Spitters, 983. This rtio s.7 (.43/ for ommon-en nd.798 (.8535/ B. plntgine - / (plnt g - B. plntgine - Y (g m = x, r =.96 A B. plntgine - (plnts m Y mx = 7.64 g m - Y = x B B. plntgine - (plnts m - Figure 3 - A Effet of B. plntgine plnt density ( on the reiprol of dry iomss yielded per plnt (/. B Effet of B. plntgine plnt density ( on dry iomss yielded per unit re (Y for lexndergrss. Therefore, it ould e expeted tht ommon-en dry iomss yielded per unity re (Y ould pproh Y mx in densities higher thn the lexndergrss ould. For the rop, suh density ould e over,38 plnts m - (Figure.B euse, up to this density, the verges of the differenes mong dry iomss yielded (Y nd Y mx ere different from zero (Tle. This nlysis suggests tht either the rop dry iomss yield ould ontinue inresing s result of the inrese in the numer of plnts per unit re, or tht the shoot s hrvested efore the totl ompetition mong plnts s estlished. There s no mention of similr results in previous ppers (Roush et l., 989; Christoffoleti & Vitori Filho, 996. Hoever, hile ommon-en nd lexndergrss ere hrvested three eeks fter seeding, Roush et l. (989 hve hrvested the het (Tritium estivum L. nd the rye grss (Lolium multiflorum Lm. fter seven eeks of groth. The minimum eed density for onstnt finl yield, similr to the mximum yield (Y mx, s eteen,9 nd,38 plnts m - euse the verge of the differenes mong the dry iomss yielded (Y nd the mximum theoretil yield (Y mx s similr to zero [(P> T =.7] (Tle 3 for the highest studied density. This indites tht t higher densities, the inrement in the dry iomss yield per unit re due to n inrement of plnts in the popultion ill e lose to zero. From these results, three totl densities ere set up to rry out three replement series tretments t one experiment. The ssumption for estlishment nd nlysis of one set of replement series tretment is tht the totl density of the speies must e higher thn the minimum hih yield is independent of the plnt density, i.e., the totl density must e eyond the point of onstnt fi- Tle - Summry of the regression nlysis of the reiprol of the dry iomss yielded per plnt (/ = plnt g - s funtion of plnt density ( = plnts m -. Soure of vrition DF Phseolus vulgris Regression Residue Coeffiient error t d Pro > T Interept Vrile X Brhiri plntgine Regression Residue Coeffiient error t Pro > T Interept Vrile X Proility of the vlue F e signifint. The vlues of the oeffiient for interept nd vrile X orrespond to, respetively, the vlues of nd of the eq. (. T test to verify if the oeffiient is similr to zero. d Proility of the oeffiient eing similr to zero. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3 SM Pro > F

6 64 Pssini et l. nl yield (Wit, ited y Roush et l., 989. Therefore, the totl density of replement series must stisfy this ssumption for oth speies. Hoever, the density from hih the rop ould reh the onstnt finl yield s not identified. Although the density found for lexndergrss (,38 plnts m - ould e used, t this density one plnt oupies m or.5 x.5 m. As the loer fesile sping for equidistnt plnts in the used pots ould e 3. x 3. m, it s deided not to follo the ssumption of the onstnt finl yield. Hoever, it s lso ssumed tht it ould hve some loss in the qulittive interprettion of the results. With regrd to the replement design ith more thn one series, there is no sientifi pper mentioning tht the totl density should ttend the requirement of the onstnt finl yield l. So, it s ssumed tht the quntittive interprettion of the results ould not e ffeted, then the totl densities in the three replement series ere set t 65; 86 nd, plnts m -, using the plnt sping of 4. x 4. m, 3.5 x 3.5 m, nd 3. x 3. m, respetively. Determintion of the ompetitiveness of ommon-en ith lexndergrss Qulittive nlysis of the speies ompetitiveness There s no effet of the totl density sine the stndrd replement series urves ere qulittively similr t eh of the three totl densities (dt not shon. Rejmánek et l. (989 ho orked ith tomto (Lyopersion esulentum Mill. nd rnyrd grss Ehinohlo rus-glli vr. frumente (Rox. W. F. Wight nd Roush et l. (989 ho orked ith het (Tritium estivum L. nd rye grss (Lolium multiflorum Lm., hve oserved similr results. So, nlysis s performed fter pooling the dt of the three replement series (Figure 4. Tle - Sttistil dt of eh tretment for the ommon-en rop. Shoot dry iomss otined t dys fter seeding. Density of ommon-en (plnts m - Dt Men (g m Men of the differene relted to Y mx ( g m error of the differene in relted to Y mx ( g m - CV % W test (Shpiro-Wilks (Pr < W.98 (.93.8 ( ( ( ( ( (.4.94 (.373 Test t ( Pr> T -.7 ( ( ( ( ( ( ( (. The theoretil dry iomss yield (Y mx lulted y the eqution of the reiprol dry iomss yielded per plnt s g m -. The ommon-en s t the V3 stge (CIAT, 983. The dt distriution of the men of the differene relted to the Y mx s norml hen Pr<W>.5. Test to verify if the mens of the differene relted to Y mx re similr to zero. Aept H hen (Pr> T >.5. Tle 3 - Sttistil dt of eh tretment for lexndergrss. Shoot dry iomss yield otined dys fter seeding. Dt error of the differene relted to Y mx ( g m CV% W test (Shpiro-Wilks (Pr < W (.5543 (.347 (.837 (.795 (.76 (.748 (.943 Test t ( Pr> T (. (. (. (.76 (.4 (.5 (.7 The theoretil mximum dry iomss yield (Y mx lulted y the eqution of the reiprol per plnt yield s 7.64 g m -. Alexndergrss s t the 4 stge (Zdoks et l., 974. The dt distriution of the men of the differene relted to the Y máx s norml hen Pr<W>.5. Test to verify if the mens of the differene relted to Y mx re similr to zero. Aept H hen (Pr> T >.5. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3 Density of lexndergrss (plnts m Men (g m Men of the differene relted to Y ( g m - m x

7 Competitivity of the ommon-en to B. plntgine 65 Even though the urve of ommon-en reltive yield s onve (Figure 4, the verges of the differenes mong the oserved reltive yields (Y r nd the orresponding vlues of the ompetitive equivlene (Y CE ere equl to zero (Pr> T >,5 (Tle 4. Hoever, the CV s higher thn 5% nd, therefore, the verges of the differenes ould e different from zero. Considering tht ommon-en reltive yield s higher thn the ompetitive equivlene line, the intrspeifi ompetition s more intense thn the interespeifi ompetition, i.e., the ompetitive effet mong ommonen plnts s higher thn the ompetitive effet of lexndergrss over ommon-en. This interprettion should e onsidered ith some ution, sine the totl density for eh replement series s loer thn tht in hih the dry iomss yielded y eh speies ould e independent of its on density. This result ould men either tht lexndergrss ould hve not ompeted ith ommon-en, or tht the rop s in suh lo density tht there s no intrspeifi ompetition, nd, therefore, there s yield response to density inrese. Hrvest mde t the V3 stge hs not shon intr nd interespeifi ompetition refleted on shoot dry iomss yield. The urve of lexndergrss reltive yield s onvex (Figure 4. The verge of the differenes mong the oserved vlues nd the orresponding vlues on the ompetitive equivlene line (CE ere different from zero (Tle 4. So tht, interspeifi ompetition s higher thn intrspeifi, ith disdvntge to lexndergrss, i.e., the ommon-en ompetitive effet over lexndergrss s higher thn the ompetition effet mong lexndergrss plnts. Reltive yield (Yr.75,75.5,5.5,5 B. plnt. P.vulg. P. vulgris B. plntgine Men of the three replement series y = -.4x +.363x +.6 r =.9995 y =.x -.97x r =.9958 Competitive equivlene line Proportions Figure 4 - Digrm of the three-replement series verge illustrting the reltive yield responses of P. vulgris nd B. plntgine to vrition in speies proportion. Proportions re expressed s perentge of the totl density. 75 5,75.75,5.5,5.5 Tle 4 - Sttistil dt of the differene eteen dry iomss reltive yield nd the vlue of the ompetitive equivlene (CE in eh proportion. The vlue of the CE t the proportions 75, 5 nd 5% s respetively,.75,.5 nd.5. Results otined t dys fter seeding. Averge of the three totl densities. Dt Phseolus vulgris Men of the reltive yield Men of the differene relted to CE error of the differene relted to CE CV % W test (Shpiro- Wilks (Pr < W (.377 (.9865 T test ( Pr> T (.3879 (.649 Brhiri plntgine Men of the reltive yield Men of the differene relted to CE error of the differene relted to CE CV % W test (Shpiro- Wilks (Pr < W (.99 (.855 T test ( Pr> T (.4 (.4 The distriution of the men differene relted to CE dt s norml hen (Pr<W>.5. The dt distriution of the men of the differene relted to the Y mx s norml hen (Pr<W>.5. Test to verify if the mens of the differene relted to Y mx re similr to zero. Aept H hen (Pr> T>.5. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3 Plnt proportions (% ( ( ( (.4

8 66 Pssini et l. In some osions, to speies hih hve similr requirements for nturl resoures n differ in their responses (Hrper, 977. The more ggressive speies ontriutes more thn the expeted to the totl yield, hile the other ontriutes less thn expeted. Therefore, one urve is onve nd the other is onvex, inditing tht the intertion eteen these speies is for the sme nturl resoures, ut one speies is more effiient in pturing them from the environment. Common-en hve proly ptured the resoures ith more effiieny thn lexndergrss (Figure 4, nd so, ommon-en s interpreted s superior ompetitor. Although plnts height nd lef re hve not een evluted s Rejmánek et l. (989 hd done, plnts of ommon-en ere oserved to emerge first nd gro fster thn lexndergrss did, presenting higher plnts nd igger lef re hih ould hve ontriuted for its etter ompetitive performne. Quntittive nlysis of the speies ompetitiveness The responses of the reiprol of dry iomss yielded per plnt of ommon-en nd per plnt of lexndergrss to the their on density nd to the density of the ompetitor speies re presented in Figures 5 nd 6. A summry of the regression nlysis is presented in Tle 5. The three-dimensionl surfe of eh grphi represents the expeted vlues derived from the experimentl dt. The reiprol of the dry iomss yielded y ommon-en (/, hs inresed y inresing the density of its plnts ( (Figure 5. By the regression eqution (eq. 4, ording to Spitters (983, the oeffiient of the rop density (, =.64 quntifies the ompetition mong ommon-en plnts (intrspeifi ompetition nd the oeffiient of the eed density (, =.3 quntifies the effet of lexndergrss over ommon-en (interspeifi ompetition. The reltive ompetitive ility (RC of the speies hih dry iomss is eing onsidered, in this se the rop, in reltion to nother speies is defined y the rtio of the regression oeffiients, /,. Adding one ommon-en plnt hs hd n equl effet on the reiprol of the dry iomss per rop plnt (/, s dding.3 lexndergrss plnts (.3 =.64/.3. In nother ords, the ddition of one ommon-en plnt hs inresed /,, i.e., redued the rop yield per plnt (, to the sme extent s the ddition of.3 lexndergrss plnts. One ommonen plnt hs sensed the presene of nother ommonen plnt s strongly s the presene of.3 lexndergrss plnts. Hoever, the proility of the interspeifi ompetition (, eing similr to zero s 9% (Tle 5, mening tht there is 9% hne tht the eed ould hve not interfered on ommon-en dry iomss. The reiprol of the dry iomss per lexndergrss plnt s redued s this speies density s inresed nd it s inresed s the ommon-en density s inresed (Figure 6. The negtive signl of the oeffiient, indites tht t eh lexndergrss plnt inrement in the mixture of plnts, /, deresed, or, inresed y.574 g. Tle 5 - Summry of the multiple liner regression nlysis of the reiprol of dry iomss yielded per plnt of ommonen (P. vulgris (/, nd of lexndergrss (B. plntgine (/ pd, s funtion of the density of the to speies ( nd. Soure of Vrition DF Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3 MS Phseolus vulgris Pro > F Regression.7.39 Residue CV R Coeffiient error t Pro > T Interept Vrile Vrile Brhiri plntgine Regression Residue CV R Coeffiient error T Pro > T Interept Vrile Vrile

9 Competitivity of the ommon-en to B. plntgine 67 3, Reiprol of P. vulgris iomss /, = x +.3 x r =.56 Reiprol of B. plntgine dry iomss /, = x +.34x r =.79 5 /, P. vulgris (plnt g -,, / pd, B. plntgine (plnt g - 4 3, B. plntgine ( P. vulgris ( B. plntgine ( P. vulgris ( Figure 5 - Comined effets of eed density ( (lexndergrss, B. plntgine nd rop density ( (ommon-ens, P. vulgris on the reiprol of dry iomss per ommonen plnt (/, (eq. 4. Figure 6 - Comined effets of eed density ( (lexndergrss, B. plntgine nd rop density ( (ommon-en, P. vulgris on the reiprol of the dry iomss per lexndergrss plnt (eq. 5. Even though not evluted, the higher the lexndergrss density, the smller its plnts ere nd less leves the plnts hd. It is possile tht lexndergrss plnts hve reruited loer mount of resoures from the environment thn ommon-en nd, even though they hd their groth stunted, they hd more mount of dry iomss umulted. The eed density oeffiient (, =.574 quntifies the ompetition mong lexndergrss plnts nd the rop density oeffiient (, =.34 quntifies the effet of the ommon-en ompetition over lexndergrss. Alexndergrss hs sensed the presene of one plnt of the sme speies s strongly s the presene of.68 ommon-en plnts (, /,. As the rop reltive ompetitive ility (RC, eq. 6 s.3 nd the eed reltive ompetitive ility (RC, eq. 7 s.68, oth speies hve suffered loer degree of ompetition ith lexndergrss s neighor. There s eologil nihe differentition euse the produt eteen the to speies reltive ompetitive ility (eq. 8 s Hoever, the nihe differentition s prtil sine the ommon-en intrspeifi ompetition s higher thn the ompetition imposed y lexndergrss plnts over ommon-en, t the sme time tht the ompetition imposed y ommon-en plnts over lexndergrss s higher thn the lexndergrss intrspeifi ompetition. Therefore, lthough the speies hve ompeted for the sme resoures, ommon-en plnts hve proly ptured environmentl resoures more effiiently thn lexndergrss plnts. Spitters (983 found nihe differentition eteen orn nd penut nd stted tht the nihe differentition is very ommon hen legume nd grss plnts re mixed. It is very likely tht this sttement n e generlized for the nihe differentition eteen ommon-en nd grss eeds. While the qulittive nlysis shoed no differene of the reltive ompetitiveness of the speies reltive to plnt densities, the quntittive nlysis deteted signifint effet of the plnt density. Roush et l. (989 lso found this ontrdition. The uthors hve suggested tht the qulittive method s less sensitive in deteting possile influenes of density on ompetitive intertions, nd tht this differene in the sensitivity of the methods my hve resulted from dt trnsformtion. While the qulittive method uses the reltive yield, the quntittive method is performed on the reiprol of yield per plnt. By the qulittive method, hen the ommonen reltive yield is onsidered, the ompetition mong ommon-en plnts s either null or higher thn the effet of lexndergrss plnts over ommon-en, nd the lexndergrss ompetitive effet over ommon-en s either null or similr to the ommon-en intrspeifi ompetition. When lexndergrss reltive yield is onsidered, the ommon-en ompetitive effet on lexndergrss s higher thn lexndergrss intrspeifi ompetition. So tht, the ommon-en reltive yield s either superior or similr to the ompetitive equivlene line, nd the lexndergrss reltive yield s inferior to this line. Therefore, ommon-en, s ompetitor speies, s superior to lexndergrss. By the quntittive method, it s evident tht there s ommonen intrspeifi ompetition nd tht the eed (4 Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3

10 68 Pssini et l. stge ffeted very little the ommon-en plnts (V3 stge. It s onfirmed tht there s no ompetition effets mong lexndergrss plnts; tht the rop effet over the eed s higher thn the ompetitive effet mong lexndergrss plnts, nd tht the eologil nihe differentition s prtil, sine the rop intrspeifi ompetition s higher thn the interspeifi, eing the ltter not signifint, nd the eed interspeifi ompetition s higher thn the intrspeifi ompetition. LITERATURE CITED CHRISTOFFOLETI, P.J.; VICTORIA FILHO, R. Efeitos d densidde e proporção de plnts de milho (Ze mys L. e ruru (Amrnthus retroflexus L. em ompetição. Plnt Dninh, v.4, p.4-47, 996. CIAT. Etps de desrrollo de l plnt de fríjol omún; guí de estudio pr ser usd omo omplemento de l Unidd udiotutoril sore el mismo tem. Cli, Colomi: CIAT, (Serie O4SB-9.3 COOLY, J. Experimentl methods in plnts ompetition reserh in ropeed systems. Weed Reserh, v.8, p , 988. COUSES, R. Aspets of the design nd interprettion of ompetition (interferene experiments. Weed Tehnology, v.5, p , 99. Reeived Deemer 7, HARPER, J.L. Popultion iology of plnts. London: Ademi Press, p. JOLLIFFE, P.A.; MIJAS, A..; RUECKLES, V.C. A reinterprettion of yield reltionships in replement series experiments. Journl of Applied Eology, v., p.7-43, 984. OLIVER, L.R.; BUCHAA, G.A. Weed ompetition nd eonomi thresholds. In: CAMPER,.D. (Ed. Reserh methods in eed siene. sl.: Southern Weed Siene Soiety of Ameri, 986. p.4, p REJMÁEK, M.; ROBISO, G.R.; REJMÁKOVÁ, E. Weed-rop ompetition: experimentl designs nd models for dt nlysis. Weed Siene, v.37, p.76-84, 989. ROUSH, M.L.; RADOSEVICH, S.R.; WAGER, R.G.; MAXWELL, B.D.; PETERSE, T.D. A omprison of methods for mesuring effets of density nd proportion in plnt ompetition experiments. Weed Siene, v.37, p.68-75, 989. SPITTERS, C.J.T. An lterntive pproh to the nlysis of mixed ropping experiments.. Estimtion of ompetition effets. etherlnds Journl of Agriulturl Siene, v.3, p.-, 983. ZADOKS, J.C.; CHAG, T.T.; KOZAK, C.F. A deiml ode for the groth stges of erels. Weed Reserh, v.4, p.45-4, 974. Sienti Agriol, v.6, n., p.59-68, Ar./Jun. 3