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DEVELOPMENT AND MORPHOMETRIC CHARACTERISTICS OF VETIVER GRASS UNDER DIFFERENT DOSES OF ORGANIC FERTILIZER Texte intégral
2021
HOLANDA, FRANCISCO SANDRO RODRIGUES | DIAS, KAROLINE LOUISE LIMA DIAS | SANTOS, LUIZ DIEGO VIDAL | BRITO, CHARLES RAMON DE MEDEIROS | MELO, JEANGELA CARLA RODRIGUES DE | SANTOS, LEANDRO SILVA
RESUMO Os usos de adubos orgânicos trazem benefícios na produção de espécies de plantas em comparação com os fertilizantes industriais, além de contribuir na conservação do solo e da água pela melhor estruturação do solo. O capim vetiver (Chrysopogon zizanioides (L.) Roberty), é amplamente utilizado em obras de bioengenharia de solos para a estabilização de encostas e taludes, aumentando a resistência do solo ao cisalhamento. O objetivo deste estudo foi avaliar o efeito do desenvolvimento do capim vetiver em diferentes doses de adubo orgânico para uso na estabilização do solo. Foi conduzido ensaio experimental em casa de vegetação, em vasos, e testadas as seguintes doses de adubo orgânico: T0- 0 g (controle); T1-135 g; T2- 270 g e T3- 405 g de adubo orgânico. Foram avaliadas as variáveis Matéria Seca da Parte Aérea (MSPA), Matéria Seca das Raízes (MSR), Comprimento de Raizes (CR), Números de Perfilhos por Planta (NPP), e Altura da Planta (AP). Os dados coletados foram submetidos a análise de regressão a 5% de probabilidade. As variáveis analisadas apresentaram valores crescentes à medida que foi disponibilizado maiores quantidades do adubo orgânico, que disponibilizou gradativamente nutrientes ao solo promovendo o melhor desenvolvimento da parte aérea pela maior disponibilidade de nitrogênio e assim potencializando maior cobertura ao solo. | ABSTRACT The use of organic fertilizers facilitates the production of plant species compared to industrial fertilizers, with a remarkable contribution to soil and water conservation through soil structuring. Vetiver grass (Chrysopogon zizanioides (L.) Roberty) is widely used in soil bioengineering projects to stabilize slopes, increasing the resistance of the soil to shear strength. The objective of this study was to evaluate the effect of the development of vetiver grass at different doses of organic fertilizer on soil stabilization. An experimental test was carried out in a greenhouse, in pots, using the following doses of organic fertilizer: T0-0 g (control); T1-135 g; T2-270 g and T3-405 g of organic fertilizer. Shoot Dry Matter (SDM), Root Dry Matter (RDM), Root Length (RL), Number of Tillers per Plant (NT) and Plant Height (PH) were evaluated. The collected data were submitted to regression analysis at 5% probability. The analysed variables showed increasing values as greater amounts of organic fertilizer, leading to an increase in soil nutrient availability and, consequently, to improved plant development.
Afficher plus [+] Moins [-]RESISTANCE ELICITORS ON PRODUCTION AND POST-PRODUCTION PERFORMANCE OF POTTED LISIANTHUS Texte intégral
2021
DIAS, MÁRCIA MARIA DE SOUZA GONDIM | SILVA, SILVANDA DE MELO | SOUSA, ALEX SANDRO BEZERRA DE | DANTAS, RENATO LIMA | ALMEIDA, VANESSA CAVALCANTE DE | NASCIMENTO, LUCIANA CORDEIRO DO
ABSTRACT Lisianthus is an important ornamental species, whose cultivation in pot still requires studies, mainly regarding the use of alternative management. Thus, the aim of this work was to evaluate the influence of resistance elicitors on the production and post-production quality of potted lisianthus. Plants grown in pots were treated with two elicitors: (E1) phosphorylated mannano-oligosaccharide and (E2) citric bioflavonoids and phytoalexins, in the doses (D) of 1 and 2pL.L-1 (E1D1 1pL.L-1, E1D2 2pL.L-1, E2D1 1pL.L-1, E2D2 2pL.L-1 and control), with 5 replications, in a completely randomized design. After opening the first flower buds, the plants remained in the greenhouse for 15 days, until they reached at least 3 open flowers, when were transferred to the room conditions (24 ± 2 oC and 72 ± 2%) for another 15 days. The application of elicitors did not influence the culture cycle or the size of the stem. There was an increase, however, in the number of viable buds and open flowers, in addition to an increase in flower’s useful life paralleled to the reduction of senescent flowers, in relation to the control. The dose of 2pL.L-1 of the E2 kept the percentage of viable open flowers in relation to the control for at least another 5 days, reducing the percentage of senescent flowers. Together, with the application of the E2 elicitor in potted lisianthus, the viability of the flowers can be prolonged, maintaining quality and delaying senescence, and, in this way, increasing the market period. | RESUMO O lisianthus é uma importante espécie ornamental, cujo cultivo em vaso ainda requer estudos, principalmente quanto ao emprego de manejo alternativo. Assim, o objetivo deste trabalho foi avaliar a influência de elicitores de resistência na produção e na qualidade pós-produção de lisianthus em vaso. Plantas de lisianthus cultivadas em vaso foram tratadas com dois elicitores: (E1) manano-oligossacarideo fosforilado e (E2) bioflavonóides e fitoalexinas cítricas, nas doses (D) de 1 e 2pL.L-1 (E1D1 1 pL.L-1, E1D2 2 pL.L-1, E2D1 1 pL.L-1, E2D2 2 pL.L-1 e controle), com 5 repetições, em delineamento inteiramente casualizado. Após a abertura dos primeiros botões florais, as plantas permaneceram na estufa durante 15 dias, até atingirem pelo menos 3 flores abertas, quando foram transferidas para a condição ambiente (24 ±2 oC e 72 ±2%) durante mais 15 dias A aplicação dos elicitores não influenciou o ciclo da cultura nem o tamanho da haste. Entretanto, observou-se aumento nos números de botões e de flores abertas viáveis, além de aumento dos dias de vida útil, paralelo à redução de flores senescentes em relação ao controle. A dose de 2 pL.L-1 de E2 manteve em, pelo menos, mais 5 dias o percentual de flores abertas viáveis com relação ao controle, reduzindo o percentual de flores senescentes. Em conjunto, com a aplicação do elicitor E2 em lisianthus em vaso pode-se prolongar a viabilidade das flores, por manter a qualidade e retardar a senescência e, assim sendo, aumentar o período de comercialização.
Afficher plus [+] Moins [-]COVER CROPS IN THE OFF-SEASON IN THE WEED MANAGEMENT AT NOTILLAGE AREA Texte intégral
2021
ARAÚJO, FERNANDO COUTO DE | NASCENTE, ADRIANO STEPHAN | GUIMARÃES, JULIANA LOURENÇO NUNES | SOUSA, VINÍCIUS SILVA | FREITAS, MARCO ANTÔNIO MOREIRA DE | SANTOS, FENELON LOURENÇO DE SOUSA
RESUMO Plantas de cobertura podem proporcionar supressão de plantas daninhas e juntamente com o controle químico compor o manejo adequado de plantas daninhas nas áreas agrícolas. O objetivo deste trabalho foi determinar o efeito do cultivo de plantas de cobertura durante a entressafra sobre o desenvolvimento de plantas daninhas em área de plantio direto. O delineamento experimental foi em blocos casualizados, com seis tratamentos e quatro repetições. Os tratamentos foram compostos das seguintes coberturas vegetais: 1. pousio (testemunha), 2. milheto (Pennisetum glaucum) + crotalárias (Crotalaria spectabilis + C. juncea + C. ochroleuca), 3. milheto + feijão-guandu (Cajanus cajans), 4. milheto + Urochloa ruziziensis, 5. milheto + Urochloa ruziziensis + feijão-guandu e 6. milheto + trigo mourisco (Fagopyrum esculentum). As avaliações foram realizadas aos 30, 75 e 225 dias após a semeadura (DAS) das plantas de cobertura. As principais plantas daninhas na área foram Cenchrus echinathus, Euphorbia heterophylla e Digitaria insularis. A área de pousio apresentou a maior quantidade, número de espécies e produção de matéria seca de plantas daninhas com densidade de 184 plantas m-2, 9,0 espécies e 527,8 g m-2 de matéria seca aos 225 DAS. Em todos os tratamentos com plantas de cobertura constatou-se que reduziu a densidade e a massa seca das plantas daninhas em comparação com o pousio, com média de 30 plantas m-2, 5,8 espécies m-1 e 7,9 g m-2 aos 225 DAS, respectivamente. Constata-se que o uso de plantas de cobertura é importante estratégia para o controle de plantas daninhas nas áreas agrícolas. | ABSTRACT Cover crops can provide suppression of weeds and together with chemical control make the proper management of weeds in agricultural areas. The objective of this study was to evaluate the effect of cover crop cultivation during the off-season on weed development in a no-tillage area. The experimental design was in randomized blocks scheme with six treatments and four replications. The treatments were: fallow (control), millet (Pennisetum glaucum) + crotalaria (Crotalaria spectabilis + C. juncea + C. ochroleuca), millet + pigeon pea (Cajanus cajans), millet + Urochloa ruziziensis, millet + Urochloa ruziziensis + pigeon pea and millet + buckwheat (Fagopyrum esculentum. The evaluations were done at 30, 75 and 225 days after sowing of the cover crops (DAS). The main growth weed species in the area were Cenchrus echinathus, Euphorbia heterophylla and Digitaria insularis. Fallow treatment showed greater number of weed species with density of 184 plants m-2, 9.0 species and with 527.8 g m-2 of dry matter mass at 225 DAS. In all treatments verified reduction in the density and mass of weeds dry matter compared to the fallow, with average of 30 plants m-2, 5.8 species and 7.9 g m-2 at 225 DAS, respectively. The use of cover crops is an important strategy for weed control in agricultural areas.
Afficher plus [+] Moins [-]NITROGEN ACCUMULATION AND EXPORT BY COMMON BEAN AS A FUNCTION OF STRAW AND N SPLITTING IN NO-TILLAGE SYSTEM Texte intégral
2021
MINGOTTE, FÁBIO LUIZ CHECCHIO | LEAL, FÁBIO TIRABOSCHI | ALMEIDA, MARCELA MIDORI YADA DE | MORELLO, ORLANDO FERREIRA | CUNHA-CHIAMOLERA, TATIANA PAGAN LOEIRO DA | LEMOS, LEANDRO BORGES
RESUMO Determinar o acúmulo e a exportação de nitrogênio (N) pelo feijoeiro em função da palhada e do seu parcelamento é importante visando o manejo e a sustentabilidade dos sistemas agrícolas. O objetivo com esse trabalho foi determinar o acúmulo e a exportação de N pelo feijoeiro cultivado sob palhada de milho ( Zea mays) e braquiária (Urochloa ruziziensis) exclusivos ou em consórcio e em função do parcelamento da adubação nitrogenada em cobertura. O experimento foi conduzido em Jaboticabal-SP-Brasil, durante a safra 2012/13, num Latossolo Vermelho eutrófico típico, sob área irrigada no sistema plantio direto. O delineamento experimental foi em blocos ao acaso com parcelas subdivididas com quatro repetições, totalizando 120 subparcelas dimensionadas em 25m2 cada. As parcelas foram constituídas pelos sistemas de cultivo antecessores ao feijoeiro: milho, milho consorciado com braquiária e braquiária. As subparcelas foram compostas por dez parcelamentos da adubação nitrogenada de cobertura (PN) estádios fenológicos V 3, V4 e R5 em diferentes combinações. A produtividade de grãos do feijoeiro difere entre os sistemas de cultivo e em função do parcelamento do N em cobertura. O cultivo exclusivo de braquiária proporciona maiores acúmulos de N na parte aérea do feijoeiro comparado ao milho e seu consórcio com braquiária. Independentemente do sistema de cultivo, a aplicação de N em cobertura em dose única de 90 kg ha-1 em V4 (terceiro trifólio) proporciona acúmulos e exportações semelhantes àqueles na ausência da adubação nitrogenada. Os parcelamentos com aplicação de N em cobertura no estádio R5 (pré-florescimento) incrementa as exportações desse nutriente no feijoeiro em sucessão ao milho e seu consórcio com braquiária. | ABSTRACT Determining nitrogen (N) accumulation and export by common bean as a function of straw and of the splitting of this nutrient is very important, aiming at the management and sustainability of agricultural systems. This study aimed to determine the N accumulation and export by common bean as a function of Zea mays and Urochloa ruziziensis grass straw (maize, maize/U. ruziziensis intercropping and U. ruziziensis) and splitting of top-dressing N fertilization. The experiment was conducted in Jaboticabal-SP-Brazil, during the 2012/13 crop season, in a Red Eutrophic Oxisol (Eutrudox) in no-tillage under irrigation. The experimental design was a randomized block with split plots with four replicates, totaling 120 subplots sized in 25m2 each. The plots consisted of the cropping systems prior to common bean: maize, maize/ U. ruziziensis intercropping and U. ruziziensis. The subplots were composed of ten top-dressing N fertilization splitting schemes (NS) at the phenological stages V3, V4 and R5 in different combinations. Common bean grain yield differs among cropping systems and as a function of top-dressed N split application. U. ruziziensis grass as single crop promotes greater N accumulation in common bean shoots compared to maize and its intercropping with U. ruziziensis grass. Regardless the cropping system, top-dressing N application in a single dose (90 kg ha-1) at V4 leads to similar accumulations and exports to those found in the absence of N fertilization. Splitting schemes with N application at the R5 stage increase the exports of this nutrient by common bean in succession to maize and its intercropping with U. ruziziensis grass.
Afficher plus [+] Moins [-]REPLACEMENT OF TIFTON 85 HAY WITH MANIÇOBA HAY IN THE SPINELESS CACTUS DIET OF SHEEP1 2 Texte intégral
2021
SANTOS, FRANCICLEIDE MARIA DE SOUZA CHARLL | LIMA JÚNIOR, DORGIVAL MORAIS DE | CARDOSO, DANIEL BARROS | MACIEL, MICHEL DO VALE | CARVALHO, FRANCISCO FERNANDO RAMOS DE
RESUMO O objetivo deste estudo foi avaliar o efeito da substituição do feno de Tifton 85 pelo feno de maniçoba em dietas à base de palma forrageira sobre a ingestão e digestibilidade de nutrientes, comportamento ingestivo e parâmetros ruminais de ovinos confinados. Foram utilizados oito ovinos machos com cânula ruminal, distribuídos em quatro níveis (0, 333, 666 e 1.000 g kg-1 de matéria seca) de substituição do feno de Tifton 85 por feno de maniçoba em delineamento quadrado latino. Os animais permaneceram confinados por 60 dias divididos em quatro períodos de 15 dias. A substituição do feno de Tifton 85 por feno de maniçoba não influenciou no consumo ou digestibilidade de matéria seca. No entanto, influenciou de forma linear negativa na digestibilidade da fibra insolúvel em detergente neutro e proteína bruta. O nitrogênio amoniacal e proteína bruta ruminal diminuiu linearmente com a substituição do feno de Tifton 85 por feno de maniçoba. Não houve efeito da substituição do feno na produção de ácidos graxos voláteis ou no biofilme microbiano. A substituição total de Tifton 85 por feno de maniçoba em rações de palma forrageira para ovinos não influenciou o consumo de nutrientes digestíveis totais, a produção de ácidos graxos voláteis ou biofilme, mas afetou a digestibilidade da proteína bruta, nitrogênio amoniacal e teor de proteína bruta no rúmen. Portanto, o feno de maniçoba pode substituir até 300 g kg-1 de feno de capim em dietas de palma forrageira para ovinos, sem comprometer o consumo e os parâmetros ruminais. | ABSTRACT The objective of this study was to evaluate the effect of replacing Tifton 85 hay with maniçoba hay in diets based on spineless cactus on the nutrient intake and digestibility, ingestive behaviour and ruminal parameters of confined sheep. In order to do this, eight male sheep with ruminal cannulae were used, distributed across four levels (0, 333, 666 and 1.000 g kg-1 of dry matter) of replacement of Tifton 85 hay with maniçoba hay in a double Latin square experimental design. The animals were confined for 60 days divided into four periods of 15 days. The replacement of Tifton 85 hay with maniçoba hay did not influence the dry matter intake or digestibility. However, it influenced in a positive linear fashion the intake of non-fibrous carbohydrates and in a linear negative fashion the digestibility of insoluble fibre in neutral detergent and crude protein. The ruminal ammonia-nitrogen and the crude protein ruminal content decreased linearly with the replacement of Tifton 85 hay with maniçoba hay. There was no effect of hay replacement on the production of volatile fatty acids or the microbial biofilm. The total replacement Tifton 85 by maniçoba hay in spineless cactus diets for sheep did not influence total digestible nutrient intake, volatile fatty acid production or biofilm, but did affect crude protein digestibility, ammonia-nitrogen and crude protein content in the rumen. Therefore, maniçoba hay can replace 300 g kg-1 grass hay in spineless cactus diets for sheep without compromising intake and ruminal parameters.
Afficher plus [+] Moins [-]BLACK OAT AND RYEGRASS INOCULATED WITH Azospirillum brasilense IN CROP-LIVESTOCK SYSTEM Texte intégral
2021
BRUM,MARCOS DA SILVA | CUNHA,VINICIUS DOS SANTOS | MARTIN,THOMAS NEWTON | ALESSIO,PEDRO GARDIN | ALMEIDA,GUILHERME ARISMENDI
ABSTRACT The success of the integrated crop-livestock system depends on the correct pasture management, particularly regarding nitrogen fertilization and grazing intensity. The objective of this study was to evaluate the total production of forage and the proportion of the botanical and structural components of black oat and annual ryegrass mixture. The experimental design was randomized blocks with three replicates and the treatments were arranged in a three-factorial scheme: seed inoculation (with and without Azospirillum brasilense inoculation), grazing management (conventional grazing, where the animals were kept in pasture with no control of pasture height; 30, 20 and 10 cm at the end of grazing, and a control without grazing), and nitrogen fertilization (0, 50 and 100 kg nitrogen ha-1). In treatments with pasture heights where grazing ended at 30, 20 and 10 cm, the height was monitored and biomass was collected when the animals entered and exited the plots. Manual separation of the components was used to determine the dry mass of green leaves, stems, senescent material and inflorescence. Total dry mass production was obtained based on the initial forage mass plus the daily accumulation rates. The proportion of structural components varied according to the different grazing managements, nitrogen doses and inoculation with Azospirillum brasilense. Biomass production of black oat and ryegrass mixture was increased by nitrogen application and Azospirillum brasilense inoculation.
Afficher plus [+] Moins [-]QUANTIFICATION OF DAMAGE AND YIELD LOSSES AND MANAGEMENT OF ROOT-KNOT NEMATODES IN CONILON COFFEE Texte intégral
2021
ZINGER,FERNANDO DOMINGO | ZINGER,LILIAN KATIANY CASTELLO RABELLO | MOARES,WILLIAN BUCKER | CAMARA,GUILHERME DE RESENDE | ALVES,FABIO RAMOS
ABSTRACT Commercial exploitation of the coffee crop is one of the most important activities in the world’s agricultural sector. One of the main phytosanitary problems affecting the crop is the presence of Meloidogyne incognita. Several measures have been tested for the management of this pathogen, albeit with low efficiency. The objective of this work was to quantify the damage and losses and to manage M. incognita race 1 with Pochonia chlamydosporia and Trichoderma harzianum biological nematicides, comparing them to a chemical nematicide. The experiment was carried out in a commercial area naturally infested by the nematode and cultivated with the conilon coffee variety ‘Vitória INCAPER 8142’, clone V02. The treatments were tested with Carbofuran nematicide and with biological nematicides composed of P. chlamydosporia Pc-10 and T. harzianum ESALQ 1306. The biological products were applied alone or in combination. The lowest NPF (final nematode population) occurred in plants treated with P. chlamydosporia and Carbofuran. P. chlamydosporia was the most effective biological agent in the management of M. incognita. There was a reduction in production with an increase in the nematode population. The highest application costs of management methods for M. incognita race 1 per hectare were for three and two applications of Carbofuran and three applications of P. chlamydosporia + T. harzianum. The treatments with lowest application costs were one application of T. harzianum and one application of P. chlamydosporia. It was concluded that all treatments were efficient for the management of M. incognita race 1, causing a decrease in the roots and soil population.
Afficher plus [+] Moins [-]RELATIVE COMPETITIVENESS BETWEEN MAIZE HYBRIDS AND WILD POINSETTIA Texte intégral
2021
GALON,LEANDRO | GABIATTI,RICARDO LUIS | BASSO,FELIPE JOSÉ MENIN | RADÜNZ,ANDRÉ LUIZ | REICHERT JÚNIOR,FRANCISCO WILSON | FIABANI,RENAN CARLOS
ABSTRACT Maize is one of the main cereals cultivated worldwide and wild poinsettia is among the weeds that cause damage in grain production. The objective of this study was to evaluate the relative competitive ability of maize hybrids in the presence of a wild poinsettia biotype through experiments in replacement series. In preliminary experiments, it was determined the plant population in which the dry mass becomes constant. For the maize hybrids ‘Agroeste’, ‘Morgan’, ‘Nidera’, and ‘Velox’, as well as the wild poinsettia, the population was 20 individuals vase-1. Subsequently, experiments were carried out in replacement series in different combinations of species that varied the relative proportions (100:0, 75:25, 50:50, 25:75, and 0:100%). The analysis of the species' competitiveness was carried out using diagrams applied to the replacement experiments and by the relative competitiveness indexes. The height (PH), chlorophyll index (CI), leaf area (LA), and the shoot dry mass (DM) of the plants were evaluated 50 days after emergence. There was competition between the maize hybrids and the wild poinsettia; both were negatively affected, regardless of the proportion of plants, causing reductions in the species' PH, CI, LA, and DM. The competition between maize and wild poinsettia occurs for the same resources in the environment, and interspecific competition caused greater damage to maize and wild poinsettia than intraspecific competition. In general, it was observed that only the hybrids ‘Nidera’ and ‘Velox’ were more competitive than the wild poinsettia.
Afficher plus [+] Moins [-]QUANTITATIVE PARAMETERS OF FLORAL STEMS OF GLADIOLUS PLANTS GROWN UNDER MINIMUM TILLAGE SYSTEM IN SANTA CATARINA, BRAZIL Texte intégral
2021
BOSCO,LEOSANE CRISTINA | STANCK,LUCIANE TEIXEIRA | SOUZA,ALEXANDRA GOEDE DE | ROSSATO,OTAVIO BAGIOTTO | UHLMANN,LILIAN OSMARI | STRECK,NEREU AUGUSTO
ABSTRACT The objective of this work was to characterize the commercial quantitative standards of floral stems of gladiolus plants grown under minimum tillage and conventional systems in two harvest seasons in the state of Santa Catarina, Brazil. Experiments were conducted in locations with subtropical climate using soils classified as Typic Dystrudept (Cambissolo) and Typic Hapludox (Nitossolo). Gladiolus plants were grown in beds with intensive soil turning, and under minimum tillage system, in which soil turning was done only in the planting rows. Plants of the cultivars Red Beauty and White Goddess were evaluated in two harvest seasons, Mothers' Day, and Valentine's Day. A completely randomized experimental design with 12 replications was used; the treatments consisted of two harvest seasons and two soil management systems. The flower stem and inflorescence lengths, stem thickness, and number of florets were measured when the plants were at the harvest point to characterize their commercial quantitative standards. These data were used to distribute the stems into four classes (75, 90, 110 and non-marketable). The stem standard of gladiolus plants grown under minimum tillage system and the edaphoclimatic conditions of the state of Santa Catarina in the Mother's Day harvest met the flower market requirements, with most stems classified into the classes 90 and 110. Therefore, gladiolus plants can be grown under minimum tillage system without affecting the flower stem development. This work is the first step to promote the growth of flowers under a conservationist perspective, focused on a more sustainable agriculture.
Afficher plus [+] Moins [-]SOURGRASS INTERFERENCE ON SOYBEAN GROWN IN BRAZILIAN CERRADO Texte intégral
2021
BRAZ,GUILHERME BRAGA PEREIRA | CRUVINEL,ALINE GUIMARÃES | CANEPPELE,ALAN BRUNO | TAKANO,HUDSON KAGUEYAMA | SILVA,ALESSANDRO GUERRA DA | OLIVEIRA JÚNIOR,RUBEM SILVÉRIO DE
ABSTRACT Sourgrass (Digitaria insularis) is one of the main species causing significant losses in Brazilian soybean production systems. Thus, this paper aimed to evaluate sourgrass interference on soybeans grown under Cerrado conditions. Three field experiments were conducted, of which the first two (E1 and E2) simulated sourgrass after pre-sowing burndown, using plants already emerged by the time soybeans were sown; whereas the third (E3) simulated both sourgrass and soybeans emerged simultaneously. Both E1 and E2 were conducted in a randomized complete block design (RCBD) with five treatments based on sourgrass infestation densities (0, 2, 4, 6, and 8 plants m-2) and four replications. In turn, E3 was also carried out in an RCBD but with treatments arranged in a 2 x 5 factorial and four replications. The first factor comprised two soybean cultivars, while the second was sourgrass density levels, just as in E1 and E2. The results showed that increasing sourgrass densities reduced soybean yield regardless of the plant growth stage when the crop was sown. Yield losses were higher when sourgrass plants were already established by the time soybean was sown. Soybean yield losses reached up to 80% under higher sourgrass infestation levels.
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