Abstracts
This study evaluated the relative competitive ability of rice cultivars in the presence of a joint-vetch (Aeschynomene denticulata) biotype, at different replacement levels of plants in the association. The experiments were conducted in a randomized complete block design with four replications. First, it was determined the population of plants in which the final dry mass remains constant, both for the rice and for the joint-vetch (24 plants per pot). Later, two experiments were carried out to evaluate the competitiveness of the rice cultivars BRS Querência and BRS Sinuelo CL with joint-vetch plants, both conducted in replacement series, in different crop and weed combinations, varying the relative proportions of plants per pot (24:0, 18:6, 12:12, 6:18 and 0:24). Competitiveness of each species was analyzed by diagrams applied to replacement experiments and by the relative competitiveness indices. Fifty days after the emergence, tillering or number of leaves, height, leaf area and shoot dry mass were determined. Competition occurred between the rice cultivars and the joint-vetch, both were adversely affected, irrespective of the plant proportion. This resulted in reductions in all evaluated variables. Different competitive abilities were observed between rice cultivars in the presence of joint-vetch. The 'BRS Querência' was more competitive than the 'BRS Sinuelo CL' for all plant proportions and variables tested.
Oryza sativa ; plant ecology; interference
Objetivou-se com o trabalho avaliar a habilidade competitiva relativa de cultivares de arroz na presença de um biótipo de angiquinho (Aeschynomene denticulata) em diferentes proporções substitutivas de plantas na associação. Os experimentos foram instalados no delineamento de blocos casualizados, com quatro repetições. Primeiramente, tanto para o arroz quanto para o angiquinho, determinou-se a população de plantas em que a produção final de massa seca se torna constante (24 plantas vaso–1). Posteriormente instalaram-se dois experimentos para avaliar a competitividade das cultivares de arroz BRS Querência e BRS Sinuelo CL com plantas de angiquinho, ambos conduzidos em série de substituição, nas diferentes combinações da cultura e da planta daninha, variando-se as proporções relativas de plantas vaso–1 (24:0, 18:6, 12:12, 6:18 e 0:24). A análise da competitividade das espécies foi efetuada por meio de diagramas aplicados a experimentos substitutivos e também pelos índices de competitividade relativa. Aos 50 dias após a emergência das espécies efetuou-se a aferição do perfilhamento ou do número de folhas, da estatura, da área foliar e da massa seca da parte aérea das plantas. Ocorreu competição entre as cultivares de arroz e o angiquinho, sendo ambos afetados negativamente, independentemente da proporção de plantas, provocando, em todos os casos, redução das variáveis avaliadas. Foi observado diferenciação da habilidade competitiva entre as cultivares de arroz quando na presença do angiquinho. A cultivar BRS Querência foi mais competitiva que a BRS Sinuelo CL na presença do angiquinho em todas as proporções de plantas e variáveis testadas.
Oryza sativa ; ecologia de plantas; interferência
1 INTRODUCTION
The Brazilian production of rice (Oryza sativa L.) is about 12
million tonnes (Silva et al., 2013Silva, L. P., Alves, B. M., Silva, L. S., Pocojeski, E., Kaminski,
T. A., & Roberto, B. S. (2013). Adubação nitrogenada sobre rendimento
industrial e composição dos grãos de arroz irrigado. Ciência Rural, 43,
1128-1133. http://dx.doi.org/10.1590/S0103-84782013005000055.
http://dx.doi.org/10.1590/S0103-84782013...
),
representing a source of income and job in many farms in the country, besides
being one of the staple cereal foods most consumed by the population. However,
rice cultivation productivity in Brazil is still greatly affected by biotic and
abiotic factors.
Among the biotic factors that contribute most to the damage to rice crops stand
out weeds, by competing with the crop for resources available in the environment
such as water, light and nutrients. Negative effects caused by weed interference
are observed in the growth, development of crops, production and grain quality
for the industry (Agostinetto et al.,
2010Agostinetto, D., Galon, L., Silva, J. M. B. V., Tironi, S. P., &
Andres, A. (2010). Interferência e nível de dano econômico de capim-arroz sobre
o arroz em função do arranjo de plantas da cultura. Planta Daninha, 28,
993-1003. http://dx.doi.org/10.1590/S0100-83582010000500007.
http://dx.doi.org/10.1590/S0100-83582010...
, 2013Agostinetto, D., Fontana, L. C., Vargas, L., Markus, C., &
Oliveira, E. (2013). Habilidade competitiva relativa de milhã em convivência com
arroz irrigado e soja. Pesquisa Agropecuária Brasileira, 48, 1315-1322.
http://dx.doi.org/10.1590/S0100-204X2013001000002.
http://dx.doi.org/10.1590/S0100-204X2013...
; Fleck et al., 2008Fleck, N. G., Lazaroto, C. A., Schaedler, C. E., & Ferreira, F.
B. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) a herbicidas de utilização em
pós-emergência em arroz irrigado. Revista Brasileira de Agrociência, 14,
462-470.; Galon et al., 2011Galon, L., Tironi, S. P., Rocha, P. R. R., Concenço, G., Silva, A.
F., Vargas, L., Silva, A. A., Ferreira, E. A., Minella, E., Soares, E. R., &
Ferreira, F. A. (2011). Habilidade competitiva de cultivares de cevada
convivendo com azevém. Planta Daninha, 29, 771-781.
http://dx.doi.org/10.1590/S0100-83582011000400007.
http://dx.doi.org/10.1590/S0100-83582011...
). It is noteworthy that weeds can be
hosts for pests and diseases and produce allelopathic effects, even causing
losses of 52% to 100% in rice crops if no control measures are adopted,
increasing the cost of production and negatively influencing the efficiency of
crop irrigation (Fleck et al., 2008Fleck, N. G., Lazaroto, C. A., Schaedler, C. E., & Ferreira, F.
B. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) a herbicidas de utilização em
pós-emergência em arroz irrigado. Revista Brasileira de Agrociência, 14,
462-470.;
Silva & Durigan, 2009Silva, M. R. M., & Durigan, J. C. (2009). Períodos de
interferência das plantas daninhas na cultura do arroz de terras altas. II –
cultivar Caiapó. Bragantia, 68, 373-379.
http://dx.doi.org/10.1590/S0006-87052009000200011.
http://dx.doi.org/10.1590/S0006-87052009...
).
Aeschynomene is a genus of weed infesting rice, containing many
species, also commonly called joint-vetch in rice producing areas in southern
Brazil (Fleck et al., 2008Fleck, N. G., Lazaroto, C. A., Schaedler, C. E., & Ferreira, F.
B. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) a herbicidas de utilização em
pós-emergência em arroz irrigado. Revista Brasileira de Agrociência, 14,
462-470.). It is
present in almost 30% of the area cultivated with rice in Rio Grande do Sul
State, causing great losses in productivity and quality of the harvested grain,
especially for the regions of the South Coast, Central Depression and West
Border, which have the highest infestation of the weed (Andres & Theisen, 2009Andres, A., & Theisen, G. (2009). Épocas de controle de
angiquinho e prejuízos em arroz irrigado cv. BRS QUERÊNCIA (Boletim de Pesquisa
e Desenvolvimento, Vol. 93). Pelotas: Embrapa Clima Temperado.). Given the poor control of
weeds in these regions and also considering the annual cycle, dispersal and
propagation by seeds and the difficulty of crop rotation makes joint-vetch the
most problematic weed in rice cultivation (Lazaroto et al., 2008Lazaroto, C. A., Fleck, N. G., Ferreira, F. B., & Schaedler, C.
E. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) ao herbicida Only. Revista Brasileira
de Agrociência, 14, 117-120.). Another factor that enhances the negative
effects of competition of weeds and rice is the low competitive ability of this
cereal (Velho et al., 2012Velho, G. F., Crusciol, C. A. C., Velini, E. D., Castro, G. S. A.,
& Borghi, E. (2012). Interferência de Brachiaria
plantaginea com a cultura do arroz, cv. Primavera. Planta Daninha,
30, 17-26. http://dx.doi.org/10.1590/S0100-83582012000100003.
http://dx.doi.org/10.1590/S0100-83582012...
).
Andres & Theisen (2009)Andres, A., & Theisen, G. (2009). Épocas de controle de angiquinho e prejuízos em arroz irrigado cv. BRS QUERÊNCIA (Boletim de Pesquisa e Desenvolvimento, Vol. 93). Pelotas: Embrapa Clima Temperado. observed reduction of over 57% in the grain yield of the rice cultivar BRS Querencia, under competition with joint-vetch at a density between 25 and 31 plants m–2.
In crops, the population of cultivated plants is usually constant whereas the
population of weeds varies according to the soil seed bank and the environmental
conditions that change the infestation level (Agostinetto et al., 2008Agostinetto, D., Rigoli, R. P., Schaedler, C. E., Tironi, S. P.,
& Santos, L. D. (2008). Período crítico de competição de plantas daninhas
com a cultura do trigo. Planta Daninha, 26, 271-278.
http://dx.doi.org/10.1590/S0100-83582008000200003.
http://dx.doi.org/10.1590/S0100-83582008...
, 2013Agostinetto, D., Fontana, L. C., Vargas, L., Markus, C., &
Oliveira, E. (2013). Habilidade competitiva relativa de milhã em convivência com
arroz irrigado e soja. Pesquisa Agropecuária Brasileira, 48, 1315-1322.
http://dx.doi.org/10.1590/S0100-204X2013001000002.
http://dx.doi.org/10.1590/S0100-204X2013...
; Galon et al., 2011Galon, L., Tironi, S. P., Rocha, P. R. R., Concenço, G., Silva, A.
F., Vargas, L., Silva, A. A., Ferreira, E. A., Minella, E., Soares, E. R., &
Ferreira, F. A. (2011). Habilidade competitiva de cultivares de cevada
convivendo com azevém. Planta Daninha, 29, 771-781.
http://dx.doi.org/10.1590/S0100-83582011000400007.
http://dx.doi.org/10.1590/S0100-83582011...
).
Thus, in studies on competition, it is necessary to evaluate not only the plant
population in the competitive process, but also the influence of the variation
in the proportion between the species (Christoffoleti & Victória, 1996Christoffoleti, P. J., & Victória, R., Fo. (1996). Efeitos da
densidade e proporção de plantas de milho (. Zea mays L.) e
caruru (Amaranthus retroflexus L.) em competiçãoPlanta Daninha,
14, 42-47.).
Determination of competitive interactions between crops and weeds requires
appropriate experimental designs and methods of analysis, and the conventional
replacement series experiments are the most used to clarify these relationships
(Agostinetto et al., 2013Agostinetto, D., Fontana, L. C., Vargas, L., Markus, C., &
Oliveira, E. (2013). Habilidade competitiva relativa de milhã em convivência com
arroz irrigado e soja. Pesquisa Agropecuária Brasileira, 48, 1315-1322.
http://dx.doi.org/10.1590/S0100-204X2013001000002.
http://dx.doi.org/10.1590/S0100-204X2013...
; Cralle et al., 2003Cralle, H. T., Fojtasek, T. B. F., Carson, K. H., Chandler, J. M.,
Miller, T. D., Senseman, S. A., Bovey, R. W., & Stone, M. J. (2003). Wheat
and Italian ryegrass () competition as affected by phosphorus nutrition.
Lolium multiflorumWeed Science, 51, 425-429.
http://dx.doi.org/10.1614/0043-1745(2003)051[0425:WAIRLM]2.0.CO;2.
http://dx.doi.org/10.1614/0043-1745(2003...
; Crotser & Witt, 2000Crotser, M. P., & Witt, W. W. (2000). Effect of Glycine max
canopy characteristics, G. max interference, and weed-free period on growth.
Solanum ptycanthumWeed Science, 48, 20-26.
http://dx.doi.org/10.1614/0043-1745(2000)048[0020:EOGMCC]2.0.CO;2.
http://dx.doi.org/10.1614/0043-1745(2000...
; Estorninos et al., 2002Estorninos, L. E., Jr., Gealy, D. R., & Talbet, R. E. (2002).
Growth response of rice () and red rice (. Oryza
sativaO. sativa) in replacement series studyWeed
Technology, 16, 401-406.
http://dx.doi.org/10.1614/0890-037X(2002)016[0401:GROROS]2.0.CO;2.
http://dx.doi.org/10.1614/0890-037X(2002...
; Roush et
al., 1989Roush, M. L., Radosevich, S. R., Wagner, R. G., Maxwell, B. D.,
& Petersen, T. D. (1989). A comparison of methods for measuring effects of
density and proporcion in plant competition experiments. Weed Science, 37,
268-275.; Vida et al.,
2006Vida, F. B. P., Laca, E. A., Mackill, D. J., Fernández, G. M., &
Fischer, A. J. (2006). Relating rice traits to weed competitiveness and yield: A
path analysis. Weed Science, 54, 1122-1131.
http://dx.doi.org/10.1614/WS-06-042R.1.
http://dx.doi.org/10.1614/WS-06-042R.1...
). In these experiments, the crops generally achieve greater
competitive ability than weeds. In the field, the effect of weed on culture is
mainly related to the level of infestation and not to its individual competitive
ability (Vilà et al., 2004Vilà, M., Williamson, M., & Lonsdale, M. (2004). Competition
experiments on alien weeds with crops: Lessons for measuring plant invasion
impact? Biological Invasions, 6, 59-69.
http://dx.doi.org/10.1023/B:BINV.0000010122.77024.8a.
http://dx.doi.org/10.1023/B:BINV.0000010...
). However,
when there is competition between individuals of the same genus and/or species,
the competitive advantage of the crop can be changed, once both exploit the same
ecological niche.
In this context, considering the wide distribution, infestation and losses caused by joint-vetch to irrigated rice fields in Rio Grande do Sul State, associated with lack of studies on the interference of this plant on the irrigated rice, this study evaluated the competitive ability between irrigated rice cultivars and a biotype of joint-vetch (Aeschynomene denticulata), at different proportions of plants in the association.
2 MATERIAL AND METHOD
The experiments were conducted at the Federal University of Pampa (UNIPAMPA), municipality of Itaqui (RS), in a greenhouse, between September and December 2011. The experimental units were plastic pots with a capacity of 8 dm3, filled with soil from a paddy field, classified as haplic plinthosol. The amendment of soil fertility was performed according to the technical recommendations for irrigated rice (SOSBAI, 2010Sociedade Sul-Brasileira de Arroz Irrigado – SOSBAI (2010). Arroz irrigado: recomendações técnicas da pesquisa para o Sul do Brasil. Porto Alegre: SOSBAI.). The physical and chemical characteristics of the soil were: pH 4.8 in water; OM = 4.7 dag kg–1; P = 6.8 mg dm–3; K = 48 mg dm–3; Al3+ = 0.5 cmolc dm–3; Ca2+ = 4.76 cmolc dm–3; Mg2+ = 1.03 cmolc dm–3; CEC (t) = 6.4 cmolc dm–3; CEC (T) = 15.6 cmolc dm–3; H+Al = 9.7 cmolc dm–3; SB = 60.59 cmolc dm–3; V = 38%; and clay = 20%.
In all experiments, we adopted the randomized complete block with four replications. Competitors tested included the rice cultivars recommended for cultivation in the Rio Grande do Sul State, namely BRS Sinuelo CL (Clearfield®) of mid-cycle (121-135 days), with modern type plants, good tolerance to lodging and diseases, smooth leaves, thin long grain with smooth hulls (SOSBAI, 2010Sociedade Sul-Brasileira de Arroz Irrigado – SOSBAI (2010). Arroz irrigado: recomendações técnicas da pesquisa para o Sul do Brasil. Porto Alegre: SOSBAI.) and the BRS Querência early cycle (106-120 days) with “modern American”, smooth leaves and grain strong stems, high tillering capacity, large number of fertile spikelets, with moderate resistance to diseases (SOSBAI, 2010Sociedade Sul-Brasileira de Arroz Irrigado – SOSBAI (2010). Arroz irrigado: recomendações técnicas da pesquisa para o Sul do Brasil. Porto Alegre: SOSBAI.). These cultivars competed with a biotype of joint-vetch (Aeschynomene denticulata).
Preliminarily, both for the rice and the joint-vetch in monoculture, we performed an experiment to estimate the plant population in which the dry mass production remains constant. To this end, we used populations of 1, 2, 4, 8, 16, 24, 32, 40, 48, 56 and 64 plants per pot (equivalent to 25, 49, 98, 196, 392, 587, 784, 980, 1,176, 1,372 and 1,568 plants m–2). The constant final production was achieved with a population of 24 plants per pot, for all cultivars tested under competition with joint-vetch, which amounted to 587 plants m–2 (data not shown).
Two other replacement series experiments were conducted to evaluate the competitiveness of rice cultivars BRS Querência and BRS Sinuelo CL with joint-vetch plants, with different combinations of cultivars and the weed biotype, varying the relative proportions of plants per pot (24:0, 18:6, 24:12, 6:18, 0:24), maintaining a constant total number of plants (24 plants per pot). To establish the desired populations for each treatment and achieve uniformity of seedlings, seeds were previously allocated on trays, and later transplanted to pots.
Fifty days after the emergence, we performed the measurement of rice tillering or the number of composite leaves of joint-vetch, height, leaf area (LA) and shoot dry mass (DM) of the rice and of the joint-vetch. The number of tillers (rice) or composite from the soil surface to the last fully expanded leaf. Leaf area was determined with the aid of an electronic integrator (Licor 3100), by collecting all the plants in each treatment. After quantification of LA, shoots were placed in paper bags and dried in a forced air circulation oven at 60 ± 5 °C to constant mass.
Data were analyzed by graphs illustrating the variation or relative yield (Bianchi et al., 2006Bianchi, M. A., Fleck, N. G., & Lamego, F. P. (2006). Proporção
entre plantas de soja e plantas competidoras e as relações de interferência
mútua. Ciência Rural, 36, 1380-1387.
http://dx.doi.org/10.1590/S0103-84782006000500006.
http://dx.doi.org/10.1590/S0103-84782006...
; Cousens, 1991Cousens, R. (1991). Aspects of the design and interpretation of
competition (interference) experiments. Weed Technology, 5,
664-673.;
Radosevich, 1987Radosevich, S. R. (1987). Methods to study interactions among crops
and weeds. Weed Technology, 1, 190-198.;
Roush et al., 1989Roush, M. L., Radosevich, S. R., Wagner, R. G., Maxwell, B. D.,
& Petersen, T. D. (1989). A comparison of methods for measuring effects of
density and proporcion in plant competition experiments. Weed Science, 37,
268-275.). This procedure,
also known as the conventional method for replacement experiments, involves the
construction of a diagram based on the relative and total yield or variations
(PR and PRT, respectively). When the result of PR is a straight line, it means
that the species have equivalent abilities. If the result of PR is a concave
line, it indicates loss in growth of one or both species. On the contrary, if
the PR shows a convex line, it indicates advantage in growth of one or both
species. When the PRT is equal to 1 (straight line), there is competition for
resources; if it is higher than 1 (convex line), the competition is avoided. If
the PRT is less than 1 (concave line), there is mutual impairment of growth
(Cousens, 1991Cousens, R. (1991). Aspects of the design and interpretation of
competition (interference) experiments. Weed Technology, 5,
664-673.).
Indices of relative competitiveness (CR), relative clustering coefficient (K) and
aggressiveness (A) were calculated, in which CR is the comparative growth of
rice cultivars (X) in relation to joint-vetch (Y); K indicates the relative
dominance of one species over another, and A indicates the most aggressive
species. Thus, CR, K and A indices indicate the most competitive species and
their joint interpretation indicates with greater precision the competitiveness
of species (Cousens, 1991Cousens, R. (1991). Aspects of the design and interpretation of
competition (interference) experiments. Weed Technology, 5,
664-673.). The rice
cultivars X are more competitive than the joint-vetch Y when CR> 1,
Kx > Ky and A> 0; in turn, the joint-vetch Y is
more competitive than rice cultivars X when CR <1, Kx <
Ky and A <0 (Hoffman &
Buhler, 2002Hoffman, M. L., & Buhler, D. D. (2002). Utilizing Sorghum as a
functional model of crop weed competition. I. Establishing a competitive
hierarchy. Weed Science, 50, 466-472.
http://dx.doi.org/10.1614/0043-1745(2002)050[0466:USAAFM]2.0.CO;2.
http://dx.doi.org/10.1614/0043-1745(2002...
). To calculate these indices, we used 50:50 proportions
of the species involved in the experiment (joint-vetch and rice), or populations
of 12:12 plants per pot, using the equations: CR= PRx/PRy;
Kx= PRx/(1-PRx); Ky=
PRy/(1-PRy); A= PRx – PRy,
according to Cousens & O’Neill
(1993)Cousens, R., & O’Neill, M. (1993). Density dependence of
replacement series experiments. Oikos, 66, 347-352.
http://dx.doi.org/10.2307/3544824.
http://dx.doi.org/10.2307/3544824...
.
The statistical analysis of yield or relative variation included the calculation
of the differences in the RP values (DPR) obtained in the proportions 25%, 50%
and 75%, relative to values belonging to the hypothetical straight line at the
respective proportions, namely 0.25; 0.50 and 0.75 for PR (Bianchi et al., 2006Bianchi, M. A., Fleck, N. G., & Lamego, F. P. (2006). Proporção
entre plantas de soja e plantas competidoras e as relações de interferência
mútua. Ciência Rural, 36, 1380-1387.
http://dx.doi.org/10.1590/S0103-84782006000500006.
http://dx.doi.org/10.1590/S0103-84782006...
; Fleck et al., 2008Fleck, N. G., Lazaroto, C. A., Schaedler, C. E., & Ferreira, F.
B. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) a herbicidas de utilização em
pós-emergência em arroz irrigado. Revista Brasileira de Agrociência, 14,
462-470.). We used the t-test to test the
differences in the indices DPR, PRT, CR, K and A (Hoffman & Buhler, 2002Hoffman, M. L., & Buhler, D. D. (2002). Utilizing Sorghum as a
functional model of crop weed competition. I. Establishing a competitive
hierarchy. Weed Science, 50, 466-472.
http://dx.doi.org/10.1614/0043-1745(2002)050[0466:USAAFM]2.0.CO;2.
http://dx.doi.org/10.1614/0043-1745(2002...
; Roush et al., 1989Roush, M. L., Radosevich, S. R., Wagner, R. G., Maxwell, B. D.,
& Petersen, T. D. (1989). A comparison of methods for measuring effects of
density and proporcion in plant competition experiments. Weed Science, 37,
268-275.). The null hypothesis to test the
differences in DPR and A is that mean values are equal to zero (Ho =
0); for PRT and CR, mean values are equal to 1 (Ho = 1); and for K,
the mean differences between Kx and Ky are equal to zero
[Ho= (Kx – Ky) = 0]. The criterion for
considering the curves PR and PRT different from hypothetical lines was the
occurrence of significant differences by the t-test in at least
two proportions (Bianchi et al., 2006Bianchi, M. A., Fleck, N. G., & Lamego, F. P. (2006). Proporção
entre plantas de soja e plantas competidoras e as relações de interferência
mútua. Ciência Rural, 36, 1380-1387.
http://dx.doi.org/10.1590/S0103-84782006000500006.
http://dx.doi.org/10.1590/S0103-84782006...
;
Fleck et al., 2008Fleck, N. G., Lazaroto, C. A., Schaedler, C. E., & Ferreira, F.
B. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) a herbicidas de utilização em
pós-emergência em arroz irrigado. Revista Brasileira de Agrociência, 14,
462-470.). Similarly, for
the indices CR, K and A, there are differences in competitiveness when at least
two of them showa significant difference by the t-test.
The results obtained for rice tillering or number of composite leaves of joint-vetch, plant height, leaf area and dry mass, expressed as mean values per treatment, were subjected to analysis of variance by F-test and, whenever significant, means were compared by Dunnett’s test, considering monocultures as controls in such comparisons. For all statistical analysis we adopted p≤0.05.
3 RESULTS AND DISCUSSION
The graphical results of the lines of relative yield (PR) in relation to the expected lines, showed that rice cultivars BRS Querência and BRS Sinuelo CL when combined with the joint-vetch (competitor) have similar competitive ability for all the variables studied and at the different proportions tested (Figure 1). Total relative yield (PRT) was less than one, with significant differences for all combinations tested, evidencing a mutual impairment in all variables and proportions analyzed (Figure 1; Table 1).
Tillering (rice) or number of leaves (joint-vetch), height, leaf area and dry mass of plants. (●) Shoot dry mass of the irrigated rice cultivar (X), (o) Shoot dry mass of the joint-vetch (Y) and (▼) Total shoot dry mass (AFRT).
Relative differences for the variables tillering (rice) or number of leaves (joint-vetch), height, leaf area and shoot dry mass of the rice cultivars BRS Querência and BRS Sinuelo CL and of the joint-vetch, at 50 days after emergence. UNIPAMPA, Itaqui (RS), 2011/2012
Among the variables, the tillering or the relative number of leaves, the leaf
area (LA) and the relative dry mass (DM) showed greater reductions in the PR
curve than the relative plant height (Figure
1). The same was observed by Fleck
et al. (2008)Fleck, N. G., Lazaroto, C. A., Schaedler, C. E., & Ferreira, F.
B. (2008). Suscetibilidade de três espécies de angiquinho
(Aeschynomene spp.) a herbicidas de utilização em
pós-emergência em arroz irrigado. Revista Brasileira de Agrociência, 14,
462-470., who reported that the height of rice plants was
slightly reduced when in competition with red rice. This trend in relation to
height is probably associated with the plant strategy to capture more light,
thereby forming stems with longer internodes in the case of rice and more
etiolated stems in the case of joint-vetch, with lower investment of energy for
growth and development. This is because light is the main limiting resource in
the community (Almeida & Mundstock,
2001Almeida, L. A., & Mundstock, C. M. (2001). A qualidade da luz
afeta o Perfilhamento em plantas de trigo, quando cultivadas sob competição.
Ciência Rural, 31, 401-408.
http://dx.doi.org/10.1590/S0103-84782001000300006.
http://dx.doi.org/10.1590/S0103-84782001...
), with a key role in the initial response of a plant with higher
competitive potential (Galon et al.,
2011Galon, L., Tironi, S. P., Rocha, P. R. R., Concenço, G., Silva, A.
F., Vargas, L., Silva, A. A., Ferreira, E. A., Minella, E., Soares, E. R., &
Ferreira, F. A. (2011). Habilidade competitiva de cultivares de cevada
convivendo com azevém. Planta Daninha, 29, 771-781.
http://dx.doi.org/10.1590/S0100-83582011000400007.
http://dx.doi.org/10.1590/S0100-83582011...
; Page et al., 2010Page, E. R., Tollenaar, M., Lee, E. A., Lukens, L., & Swanton,
C. J. (2010). Shade avoidance: an integral component of cropweed competition.
Weed Research, 50, 281-288.). In
wheat, Agostinetto et al. (2008)Agostinetto, D., Rigoli, R. P., Schaedler, C. E., Tironi, S. P.,
& Santos, L. D. (2008). Período crítico de competição de plantas daninhas
com a cultura do trigo. Planta Daninha, 26, 271-278.
http://dx.doi.org/10.1590/S0100-83582008000200003.
http://dx.doi.org/10.1590/S0100-83582008...
and
Rigoli et al. (2008)Rigoli, R. P., Agostinetto, D., Schaedler, C. E., Dal Magro, T.,
& Tironi, S. (2008). Habilidade competitiva relativa do trigo () em
convivência com azevém () ou nabo (. Triticum
aestivumLolium multiflorumRaphanus
raphanistrum)Planta Daninha, 26, 93-100.
http://dx.doi.org/10.1590/S0100-83582008000100010.
http://dx.doi.org/10.1590/S0100-83582008...
registered an
increase in the height of the plants when in competition with ryegrass or
radish. Moreover, Wandscheer et al.
(2013)Wandscheer, A. C. D., Rizzardi, M. A., & Reichert, M. (2013).
Competitive ability of corn in coexistence with goosegrass. Planta Daninha, 31,
281-289. http://dx.doi.org/10.1590/S0100-83582013000200005.
http://dx.doi.org/10.1590/S0100-83582013...
evaluated the competitive ability of corn intercropped with
goosegrass (Eleusine indica) and reported that the weed
exhibited better competitive results than the crop.
In general, the differences relating to rice tillering and joint-vetch leaf
number, plant height (EP), AF and MS (Table
1) showed a greater loss of PR in the competitor in comparison with
rice cultivars, except for the number of leaves and the EP, in which the
joint-vetch was more competitive than the cultivar BRS Sinuelo CL at the
proportion 75:25. The competitive ability of rice cultivars, in the presence of
the weed, varied depending on the variable (Table 1). There were major differences in tillering and AF, with
superiority of the cultivar BRS Querência to BRS Sinuelo CL, especially with a
higher proportion of the species in relation to the competitor, with a reduction
in this difference as the proportion of competitor was increased. According to
SOSBAI (2010)Sociedade Sul-Brasileira de Arroz Irrigado – SOSBAI (2010). Arroz
irrigado: recomendações técnicas da pesquisa para o Sul do Brasil. Porto Alegre:
SOSBAI., the cultivar BRS
Querência stands out compared to other rice cultivars given the high tillering
capacity, which corroborates the results found herein. Similar results were
verified by Agostinetto et al. (2008)Agostinetto, D., Rigoli, R. P., Schaedler, C. E., Tironi, S. P.,
& Santos, L. D. (2008). Período crítico de competição de plantas daninhas
com a cultura do trigo. Planta Daninha, 26, 271-278.
http://dx.doi.org/10.1590/S0100-83582008000200003.
http://dx.doi.org/10.1590/S0100-83582008...
,
Bianchi et al. (2006)Bianchi, M. A., Fleck, N. G., & Lamego, F. P. (2006). Proporção
entre plantas de soja e plantas competidoras e as relações de interferência
mútua. Ciência Rural, 36, 1380-1387.
http://dx.doi.org/10.1590/S0103-84782006000500006.
http://dx.doi.org/10.1590/S0103-84782006...
, Galon et al. (2011)Galon, L., Tironi, S. P., Rocha, P. R. R., Concenço, G., Silva, A.
F., Vargas, L., Silva, A. A., Ferreira, E. A., Minella, E., Soares, E. R., &
Ferreira, F. A. (2011). Habilidade competitiva de cultivares de cevada
convivendo com azevém. Planta Daninha, 29, 771-781.
http://dx.doi.org/10.1590/S0100-83582011000400007.
http://dx.doi.org/10.1590/S0100-83582011...
and Wandscheer et al. (2013)Wandscheer, A. C. D., Rizzardi, M. A., & Reichert, M. (2013).
Competitive ability of corn in coexistence with goosegrass. Planta Daninha, 31,
281-289. http://dx.doi.org/10.1590/S0100-83582013000200005.
http://dx.doi.org/10.1590/S0100-83582013...
, which also
observed, when working with many species, the existence of competitive
variability according to the development cycle and the intrinsic characteristics
of each cultivar when in competition with weeds.
For the variables AF, EP and MS, rice cultivars had a similar competitiveness
(Table 1). It can be inferred that
as they are different cultivars, they express different behavior in the presence
of joint-vetch, especially the difference in the cycle, early and medium,
respectively for the BRS Querência and the BRS Sinuelo CL. Agostinetto et al. (2013)Agostinetto, D., Fontana, L. C., Vargas, L., Markus, C., &
Oliveira, E. (2013). Habilidade competitiva relativa de milhã em convivência com
arroz irrigado e soja. Pesquisa Agropecuária Brasileira, 48, 1315-1322.
http://dx.doi.org/10.1590/S0100-204X2013001000002.
http://dx.doi.org/10.1590/S0100-204X2013...
investigated rice and soybeans
competing with crabgrass (Digitaria ciliaris) and observed that
the intraspecific competition prevailed for crops, while for the weed, prevailed
interspecific competition as the most harmful.
Tillering, EP, AF and MS of rice cultivars BRS Querência and BRS Sinuelo CL were
reduced when competed with joint-vetch in all tested proportions (Table 2). There was increasing loss to
the crop, for the variables evaluated, with increasing proportion of the
competitor. The higher the proportion of plants in the association (competitor
or crop), the greater the losses in variables of rice or even weed; this
demonstrates again the competition of species for the same resources. The
results of this study are similar to several others in the literature, such as
Cerqueira et al. (2013)Cerqueira, F. B., Erasmo, E. A. L., Silva, J. I. C., Nunes, T. V.,
Carvalho, G. P., & Silva, A. A. (2013). Competition between drought-tolerant
upland rice cultivars and weeds under water stress condition. Planta Daninha,
31, 291-302. http://dx.doi.org/10.1590/S0100-83582013000200006.
http://dx.doi.org/10.1590/S0100-83582013...
when
analyzed Spermacoce verticillata competing with rice cultivars
Jatobá and Catetão; Agostinetto et al.
(2008)Agostinetto, D., Rigoli, R. P., Schaedler, C. E., Tironi, S. P.,
& Santos, L. D. (2008). Período crítico de competição de plantas daninhas
com a cultura do trigo. Planta Daninha, 26, 271-278.
http://dx.doi.org/10.1590/S0100-83582008000200003.
http://dx.doi.org/10.1590/S0100-83582008...
evaluated rice competing with barnyardgrass; and Galon et al. (2011)Galon, L., Tironi, S. P., Rocha, P. R. R., Concenço, G., Silva, A.
F., Vargas, L., Silva, A. A., Ferreira, E. A., Minella, E., Soares, E. R., &
Ferreira, F. A. (2011). Habilidade competitiva de cultivares de cevada
convivendo com azevém. Planta Daninha, 29, 771-781.
http://dx.doi.org/10.1590/S0100-83582011000400007.
http://dx.doi.org/10.1590/S0100-83582011...
who studied barley in
competition with ryegrass. All the above authors found greater reductions in
morphological variables with increasing proportion of competitor plants in the
association.
Differences between plants associated or not of the rice cultivars BRS Querência and BRS Sinuelo CL and joint-vetch for variables tillering (rice) or number of leaves (joint-vetch), height, leaf area and shoot dry mass, at 50 days after the emergence. UNIPAMPA, Itaqui (RS), 2011/2012
The BRS Querência, in the presence of different proportions of joint-vetch, experienced minor losses compared to BRS Sinuelo CL. At the proportion 75:25 (rice: competitor), as to the number of tillers, the BRS Querência was reduced by 26%, while the BRS Sinuelo CL, by 44% (Table 2).
Likewise, joint-vetch showed the greatest suppression in the number of leaves
when competing with the BRS Querência (95%) than with BRS Sinuelo CL (83%) at
75:25 (rice: competitor), demonstrating the higher competitiveness of BRS
Querência compared to BRS Sinuelo CL. Nevertheless, for the other variables, the
superiority of BRS Querência over BRS Sinuelo CL is not so evident. Importantly,
the competition was detrimental to both rice cultivars, because according to
Bianchi et al., (2006)Bianchi, M. A., Fleck, N. G., & Lamego, F. P. (2006). Proporção
entre plantas de soja e plantas competidoras e as relações de interferência
mútua. Ciência Rural, 36, 1380-1387.
http://dx.doi.org/10.1590/S0103-84782006000500006.
http://dx.doi.org/10.1590/S0103-84782006...
competition
quantitatively and qualitatively affects production, because it changes the use
efficiency of environmental resources, such as water, light, CO2 and
nutrients. Also, in a plant community, benefit in competition for resources is
given for species that establish first or by intrinsic characteristics on the
competitive ability of each cultivar (height, growth rate, number of tillers,
among others).
Besides that, when evaluating the relative competitiveness index (CR), we found higher growth in both rice cultivars compared with joint-vetch, in all variables (Table 3). Among the cultivars, BRS Querência presented greater competitive ability than BRS Sinuelo CL for all variables tested, under competition with joint-vetch. The same was observed for the coefficients of competitiveness (K); in all cases, rice showed higher values for this coefficient (Table 3). Regarding aggressiveness (A), rice was more competitive in all cases. For this index (A), the BRS Querência was more aggressive than BRS Sinuelo CL in the presence of the competitor joint-vetch (Table 3).
Indices of competitiveness between rice cultivars and competitor, expressed by relative competitiveness (CR), relative clustering coefficient (K) and aggressivity (A), obtained in experiments conducted in replacement series
In the joint interpretation of graphical analysis on the relative variables and their significance in relation to the equivalent values (Figure 1 and Table 1), morphological variables (Table 2) and the competitiveness indices (Table 3), in general, there was a negative interaction between the species, affecting both rice cultivars and the competitor (joint-vetch). Nonetheless, in this case, the competitor suffered greater losses than rice, especially when associated with BRS Querência, which was more competitive than BRS Sinuelo CL in the presence of joint-vetch.
4 CONCLUSION
There was competition between the rice cultivars BRS Querência and BRS Sinuelo CL and the joint-vetch, both were affected, regardless of the proportion of plants. In all cases, there was a reduction in tillering or number of composite leaves, in plant height in leaf area and in dry mass of the species.
The competitive ability of the BRS Querência is higher than the BRS Sinuelo CL in the presence of joint-vetch.
Rice cultivars BRS Querência and BRS Sinuelo CL have a higher competitive ability than joint-vetch.
ACKNOWLEDGEMENTS
The authors thank the National Council for Scientific and Technological Development (CNPq) for providing financial assistance, process number 483564/2010-9.
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» http://dx.doi.org/10.1590/S0100-83582013000200005
Publication Dates
-
Publication in this collection
Mar 2015
History
-
Received
12 May 2014 -
Accepted
08 Oct 2014