ABSTRACT
White clover is tolerant to many herbicides, making difficult a chemical control of this species during soybean crop establishments. The objective of this research was to select herbicides applied postemergence to control white clover in soybean and know the effects of this control on soybean yield. Seven herbicides were assessed, applied postemergence, with or without sequential application of glyphosate, and two control treatments (no control and total control of white clover). Glyphosate (with two sequential applications), fomesafen (with a sequential application of glyphosate), chlorimuron-ethyl and lactofen have shown a satisfactory control of white clover (above 80%). The lower control efficiency has resulted in lower production of soybeans.
herbicide; Integrated Crop-Livestock System; interference; Trifolium repens; Glycine max
RESUMO
O trevo-branco apresenta tolerância a diversos herbicidas, o que torna difícil o controle químico dessa espécie durante o estabelecimento da cultura da soja. Os objetivos desta pesquisa foram selecionar herbicidas utilizados em pós-emergência que controlam o trevo-branco na cultura da soja e conhecer os efeitos desse controle na produtividade da soja. Foram avaliados sete herbicidas aplicados em pós-emergência, com ou sem aplicação sequencial de glyphosate, e dois tratamentos testemunhas (sem controle e controle total do trevo-branco). Os herbicidas glyphosate (com duas aplicações sequenciais), fomesafen (com aplicação sequencial de glyphosate), chlorimuron-ethyl e lactofen apresentaram controle satisfatório do trevo-branco (acima de 80%). A menor eficiência de controle resultou em menor produção da cultura da soja.
herbicida; Sistema Integrado de Produção Agropecuária; interferência; Trifolium repens; Glycine max
INTRODUCTION
The need to increase agricultural yield in a sustainable way signals the adoption of production systems in an integrated and balanced manner (Gilbert, 2009GILBERT, N. The disappearing nutrient. Nature, v. 461, n. 8, p. 461-716, 2009.). In this context, it is necessary to search for strategies to concurrently achieve increased agricultural yield and environmental quality (Lemaire et al., 2014LEMAIRE, G. et al. Integrated crop-livestock systems: Strategies to achieve synergy between agricultural production and environmental quality. Agric. Ecosyst. Environ., v. 190, n. 1, p. 4-8, 2014.).
In response to society new demands, the Integrated Crop-Livestock System (ICLS) has emerged in order to diversify and integrate the various production systems, thus promoting more efficient use of inputs and nutrients cycling (Carvalho, 2010CARVALHO, P. C. F. et al. Managing grazing animals to achieve nutrient cycling and soil improvement in no-till integrated systems. Nutr. Cycl. Agroecosys., v. 88, n. 2, p.259-273, 2010.) and the activation of agro-ecosystems potential (Lemaire et al., 2014).
In subtropical climates, the use of ICLS with animal grazing in winter and grainproduction in summer is widespread as an important agricultural model (Moraes et al., 2014MORAES, A. et al. Integrated crop-livestock systems in the Brazilian subtropics. Eur. J. Agron., v. 57, n. 1, p. 4-9, 2014.), and the winter poaceae are the main forage used (Lustosa et al., 2011LUSTOSA, S. B. C. et al. Experiências de integração lavoura-pecuária na região central do Paraná. Synerg. Scyent., v. 6, n. 1, p.48-57, 2011.). Their intercropping with white clover (Trifolium repens), constitutes an alternative for increasing the nutritional quality of pasture, as well as biological nitrogen fixation contribution (Phelan et al., 2013PHELAN, P.; CASEY, A.; HUMPHREYS, J. The effect of target postgrazing height on sward clover content, herbage yield, and dairy production from grass-white clover pasture. J. Dairy Sci., v. 96, n. 13, p. 1598-1611, 2013.; Cougnon et al., 2014COUGNON, M. et al. Performance and quality of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) and mixtures of both species grown with or without white clover (Trifolium repens L.) under cutting management. Forage Sci., v. 69, n. 4, p. 666-677, 2014.).
When using white clover (WC) in the composition of winter pastures, one should take into account that it is a perennial legume. Thus, if unchecked after use, it remains in the area, becoming a competing plant with the subsequent grains crop. An aggravating factor is that this crop is tolerant to several herbicides used to control broadleaf plants (Machado et al., 2013MACHADO, D. et al. Seletividade de herbicidas em trevo-branco no estádio fenológico de expansão do primeiro trifólio. Ci. Rural, v. 43, n. 12, p. 2132-2138, 2013.; Mccurdy et al., 2013McCURDY, J. D.; McELROY, J. S.; FLESSNER, M. L. Differential Response of Four Trifolium Species to Common Broadleaf Herbicides: Implications for Mixed Grass-Legume Swards. Weed Technol., v. 27, n. 1, p. 123-128, 2013.), which can hamper the chemical control of WC.
Among the grains produced in a subtropical climate during the summer, soybeans stand out as one of the most important due to their international representation. The lack of weed control in crops can lead to productivity losses up to 73% (Fickett et al., 2013FICKETT, N. D.; BOERBOOM, C. M.; STOLTENBERG, D. E. Soybean yield loss potential associated with early-season weed competition across 64 site-years. Weed Sci., v. 61, n. 3, p. 500-507, 2013.). Their cultivation in areas with production systems integrated with WC becomes difficult due to the lack of information about which active ingredients applied postemergence can be used for WC tillage in soybeans crop.
The objectives of this research were to select herbicides for use in efficient postemergence in white clover control in soybeans crop and to quantify the effect of this control on soybeans production.
MATERIALS AND METHODS
The experiment was conducted in an experimental field located at 25o23'36 "S and 51o27'19" W, in a typical and very clayeytextured aluminic oxisol bruno (Embrapa, 2006). The local climate is Cfb (mesothermal humid subtropical), with no dry season, with cool summers and mild winters, according to the Köppen-Geiger classification. The average annual rainfall is 1,944 mm, the average annual minimum temperatures are 12.7 oC and the maximum are 23.5 oC.
The experimental design was a randomized complete block design with three replications in a 7 x 2 + 2 factorial arrangement, with seven herbicide applications in postemergence combined or not with a sequential application of glyphosate (720 g ha-1) and two additional controls (without control and with total control of WC), totaling 16 treatments. The herbicides used were bentazon (600 g ha-1), chlorimuron-ethyl (250 g ha-1), imazethapyr (100 g ha-1), fomesafen (250 g ha-1), lactofen (240 g ha-1) and imazamox + bentazon (600 + 28 g ha-1). Each experimental plot had five soybean rows spaced 0.40 m by 8 m long.
The implementation of WC occurred in April 2012 with cultivar Zapicán inoculated with Rhizobium leguminosarum bv. trifolli (10 mL kg-1). Sowing was done in furrows spaced 0.18 m, depth of 0.05 m and density of 8 kg ha-1, with a base fertilization of 120 kg ha-1 of P2O5, 60 kg ha-1 of K2O and 1.2 kg ha-1 of B.
Desiccation of the area containing WC and spontaneous winter forage was carried out with an application of glyphosate (720 g ha-1) in November. Sowing of soybean BMX Apolo(r) RR occurred eight days later, following technical recommendations for crops.
When soybeans reached the V2 stage (14 DAE), treatments were applied in postemergence for control of the WC remaining from the application of glyphosate in desiccation, which presented 96.02 ± 8.8 g m-2 of DM at that time.
A sprayer pressurized with CO2 and constant pressure of 50 lb inch-2 was used, equipped with a fan-type four-tips bar with 110:0.2 air induction, spaced 0.50 m and spray volume of 190 L ha-1. At the time of application, the plant surface was dry, relative humidity was 73.6% and temperature 21.3 oC.
WC and other weeds were collected at 0, 7, 21, 35 and 70 days after application (DAA) in postemergence, cutting at ground level was held, using a square of 0.16 m2 to determine the dry matter (DM). Subsequently, to quantify the DM reduction speed of WC by the treatments, a linear regression was adjusted (y = ax + b), which intercepted the point of dry matter before application of treatments.
The control efficacy of WC by the treatments was determined using the obtained control percentage, calculated by the following mathematical expression (Barros et al., 2007BARROS, J. F. C.; BASCH, G.; CARVALHO, M. Effect of reduced doses of a post-emergence herbicide to control grass and broad-leaved weeds in no-till wheat under Mediterranean conditions. Crop Protec., v. 26, n. 10, p. 1538-1545, 2007.):
where: Ef is the treatment efficiency (%); C1 is the dry matter of WC per square meter collected prior to application of the treatments; C2 is the dry matter of WC per square meter collected 10 weeks after application of the treatment in soybean in R2; and d is the difference between the dry matter of white clover per square meter between the first and second assessments in the treatment without the application of the herbicide. Thus, this mathematical expression includes as control not only the reduction in DM, but also its amount that WC stopped growing, being more suitable for perennial species, as maintaining them without growth also characterizes control.
Soybean plants were harvested at the R8 stage in 2 linear meters in the three central rows of each plot. The grain moisture was adjusted to 13% to determine productivity.
Coefficient a of dry matter reduction regression of WC underwent - along with the variables efficiency of control of WC, DM of WC, DM of other weeds and soybeans yield - analysis of variance and the averages were compared by Duncan test (p < 0.01).
RESULTS AND DISCUSSION
Chemical control of WC provided by the herbicides applied postemergence in soybeans crops shows that bentazon, imazethapyr, fomesafen e imazamox+bentazon do not present a satisfactory performance (< 50% of control) (Table 1). Glyphosate applied postemergence again presented WC control of 63.64% and chlorimuron-ethyl and lactofen showed a satisfactory performance (> 80% of control) (Table 1). Still, the sequential application of glyphosate after the application of fomesafen and glyphosate treatments resulted in a satisfactory control (Table 1).
Regarding DM of WC, at 70 DAA of the herbicides, treatments with lactofen and chlorimuron-ethyl had the lowest averages, with 20.54 and 19.94 g m-2, respectively (Table 1). The sequential application of glyphosate had a positive effect on these treatments, but the DM of WC did not differ for chlorimuron-ethyl. The WC control increased from a reduction in DM of -1.012 e -1,051 to -1.169 and -1,404 g m-2day-1 for lactofen and chlorimuron-ethyl, respectively, with the sequential application of glyphosate (Table 1).
Of the herbicides of application in postemergence that did not show a satisfactory control of WC (< 50% control), bentazon and imazethapyr resulted in the growth of WC after its application, and this is of 0.359 and 0.508 g m-2day-1, respectively (Table 1). Mc Curdy et al. (2013) and Machado et al., (2013), studying herbicides selective to WC crop, have identified bentazon and imazethapyr as selective to crops, agreeing with the results obtained in this study (Table 1).
The highest yield was obtained in the control with full control of WC with 3.72 Mg ha-1, followed by lactofen treatment with a sequential application of glyphosate, with a productivity of 3.50 Mg ha-1 (Table 2). The lower yields were encountered in the unsprayed controls and in the treatment with an isolated application of chlorimuron-ethyl, this being of 0.39 and 0.98 Mg ha-1, respectively (Table 2).
It is noteworthy that the herbicides used,though selective to crops, cause an effect that is phytotoxic to soybeans. However, works such as the one by Souza et al. (2002)SOUZA, R.T. Seletividade de combinações de Herbicidas Latifolicidas com Lactofen para a cultura de soja. Sci. Agric., v. 59, n. 1, p. 99-106, 2002. reveal that at 20 DAA of the herbicides these effects disappear, not significantly changing the soybean crop production.
Further, for yield (Table 2), the greater the control of WC, the higher the productivity per area, except for two treatments, being the ones with an application of chlorimuron-ethyl and lactofen. These treatments have shown the higher amounts of DM of other weeds, with 35.19 and 49.16 g m-2, respectively (Table 2).
For latifolicide treatments without a sequential glyphosate application, it is possible to see that the greater the control of WC, the higher the occurrence of other weeds (Table 2), since, with the exception of glyphosate, all other treatments have not shown action control over narrow-leaf species. The reduction in the expression of the seed bank by the presence of WC is linked to the fact that the forage, when established, promotes the soil cover, preventing the emergence of other weeds (Den Hollander et al., 2007Den HOLLANDER, N. G.; BASTIAANS, L.; KROPFF, M.J. Clover as a cover crop for weed suppression in an intercropping design I. Characteristics of several clover species. Eur. J. Agron., v. 26, n. 2, p. 92-103, 2007a.a, b; Wortman et al., 2013WORTMAN, S. E. et al. Mechanical termination of diverse cover crop mixtures for improved weed suppression in organic cropping systems. Weed Sci., v. 61, n. 1, p. 162-170, 2013.). Thus, the greater the control of WC, the greater the expression of the soil seed bank of other weeds.
It should be noted that, for a satisfactory control of WC only with glyphosate, it is required, in addition to the application to the drying area, two more postemergence applications, resulting in an amount of 2,160 g ha-1. Considering the issue of increasing weed resistance to glyphosate and the intensification in the use of glyphosate being a factor in their selection (Beckie, 2011BECKIE, H.J. Herbicide-resistant weed management: focus on glyphosate. Pest Manag. Sci., v. 67, n. 1, p. 1037-1048, 2011.), preference should be given to the rotation of molecules for the control of WC.
Given the results, it is concluded that the presence of WC reduces soybean production, characterizing the need for its control. Among the tested herbicides applied in postemergence, glyphosate (with two sequential applications), fomesafen (with a sequential application of glyphosate), chlorimuron-ethyl and lactofen have shown a satisfactory control of WC (> 80%). Treatment with lactofen plus another sequential application of glyphosate has provided the highest soybean production.
ACKNOWLEDGMENT
To Coordination of Improvement of Higher Education (CAPES) for the financial support in carrying out this work.
LITERATURE CITED
- BARROS, J. F. C.; BASCH, G.; CARVALHO, M. Effect of reduced doses of a post-emergence herbicide to control grass and broad-leaved weeds in no-till wheat under Mediterranean conditions. Crop Protec., v. 26, n. 10, p. 1538-1545, 2007.
- BECKIE, H.J. Herbicide-resistant weed management: focus on glyphosate. Pest Manag. Sci., v. 67, n. 1, p. 1037-1048, 2011.
- CARVALHO, P. C. F. et al. Managing grazing animals to achieve nutrient cycling and soil improvement in no-till integrated systems. Nutr. Cycl. Agroecosys., v. 88, n. 2, p.259-273, 2010.
- COUGNON, M. et al. Performance and quality of tall fescue (Festuca arundinacea Schreb.) and perennial ryegrass (Lolium perenne L.) and mixtures of both species grown with or without white clover (Trifolium repens L.) under cutting management. Forage Sci., v. 69, n. 4, p. 666-677, 2014.
- Den HOLLANDER, N. G.; BASTIAANS, L.; KROPFF, M.J. Clover as a cover crop for weed suppression in an intercropping design I. Characteristics of several clover species. Eur. J. Agron., v. 26, n. 2, p. 92-103, 2007a.
- Den HOLLANDER, N. G.; BASTIAANS, L.; KROPFF, M. J. Clover as a cover crop for weed suppression in an intercropping design II. Competitive ability of several clover species. Eur. J. Agron., v. 26, n. 2, p. 104-112, 2007b.
- EMPRESA BRASILEIRA DE PESQUISA AGROPECUÁRIA - EMBRAPA. Sistema brasileiro de classificação de solos. 2. ed. Rio de Janeiro: 2006. 306 p.
- FICKETT, N. D.; BOERBOOM, C. M.; STOLTENBERG, D. E. Soybean yield loss potential associated with early-season weed competition across 64 site-years. Weed Sci., v. 61, n. 3, p. 500-507, 2013.
- GILBERT, N. The disappearing nutrient. Nature, v. 461, n. 8, p. 461-716, 2009.
- LEMAIRE, G. et al. Integrated crop-livestock systems: Strategies to achieve synergy between agricultural production and environmental quality. Agric. Ecosyst. Environ., v. 190, n. 1, p. 4-8, 2014.
- LUSTOSA, S. B. C. et al. Experiências de integração lavoura-pecuária na região central do Paraná. Synerg. Scyent., v. 6, n. 1, p.48-57, 2011.
- MACHADO, D. et al. Seletividade de herbicidas em trevo-branco no estádio fenológico de expansão do primeiro trifólio. Ci. Rural, v. 43, n. 12, p. 2132-2138, 2013.
- McCURDY, J. D.; McELROY, J. S.; FLESSNER, M. L. Differential Response of Four Trifolium Species to Common Broadleaf Herbicides: Implications for Mixed Grass-Legume Swards. Weed Technol., v. 27, n. 1, p. 123-128, 2013.
- MORAES, A. et al. Integrated crop-livestock systems in the Brazilian subtropics. Eur. J. Agron., v. 57, n. 1, p. 4-9, 2014.
- PHELAN, P.; CASEY, A.; HUMPHREYS, J. The effect of target postgrazing height on sward clover content, herbage yield, and dairy production from grass-white clover pasture. J. Dairy Sci., v. 96, n. 13, p. 1598-1611, 2013.
- SOUZA, R.T. Seletividade de combinações de Herbicidas Latifolicidas com Lactofen para a cultura de soja. Sci. Agric., v. 59, n. 1, p. 99-106, 2002.
- WORTMAN, S. E. et al. Mechanical termination of diverse cover crop mixtures for improved weed suppression in organic cropping systems. Weed Sci., v. 61, n. 1, p. 162-170, 2013.
Publication Dates
-
Publication in this collection
Jul-Sep 2015
History
-
Received
09 June 2015 -
Accepted
11 June 2015