ABSTRACT Several species of harmful grass weeds were voluntarily brought in by man, mainly with the specific purpose of produce forage. These species compete with crops for physical area and environmental resources, can host pests and diseases, and interfere on harvesting. This work aimed to evaluate in field conditions, the effects of different specific seed weight and sowing depths on the emergence of the species Urochloa brizantha cv. marandú. It was adopted a randomized blocks design with four replications and the treatments arranged in a 6 x 3 factorial scheme, with six sowing depths (1.0, 2.0, 4.0, 8.0, 12.0 and 16.0 cm) and three specific seed weight (low, medium, and high). The treatment effects were evaluated by seedling emergence in field. The marandu-grass seedlings emerged until 12 cm depth, regardless of specific seed weight and year. Sowing depths between 1.0 and 4.0 cm depth have promoted the greater percentage of emergence, and the lowest average time and speed index for emergence of seedlings on field, regardless of the specific seed weight. High-specific weight seeds resulted in greater percentage of emergence on field, speed and synchronicity index of emergence of marandú-grass seedlings. Sowing depths higher than 1.0 cm induces a delay on marandú-grass propagation. man forage resources diseases harvesting conditions cv marandú scheme 1.0, 10 1 0 (1.0 20 2 2.0 40 4 80 8 8.0 120 12. 160 16 16. low, low (low medium high. high . high) marandugrass marandu year 1. 4. Highspecific High marandúgrass propagation (1. 2. 8. (1 (

RESUMO Compreender os aspectos de emergência e desenvolvimento de plantas daninhas é essencial na tomada de decisão para estratégias de manejo. Neste trabalho foram avaliados em condições de campo, os efeitos de diferentes profundidades de semeadura e intensidades luminosas na emergência e no desenvolvimento das plantas daninhas Sida rhombifolia e Senna obtusifolia. Cada espécie constituiu um experimento e o delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 6 x 4, sendo o primeiro fator correspondente as seis profundidades de semeadura (0,5; 1,0; 2,0; 4,0; 8,0 e 12,0 cm) e o segundo a quatro intensidades luminosas (100%, 70%, 50% e 30% da luz solar). Avaliou-se diariamente a emergência das plântulas para obtenção da emergência e do índice de velocidade de emergência. A altura, o tempo até a indução floral e a matéria seca das plantas no florescimento também foram avaliadas. Quando submetidas a diferentes níveis de sombreamento as plântulas de S. rhombifolia emergem em até 12,0 cm de profundidade. As plântulas de S. obtusifolia emergem em todas as profundidades de semeadura, mesmo quando submetidas a diferentes intensidades de radiação solar. As plântulas das espécies S. rhombifolia e S. obtusifolia emergem menos e em menor velocidade em semeaduras entre 8,0 e 12,0 cm de profundidade e se desenvolvem melhor em condições de luz solar plena em semeaduras entre 1,0 e 4,0 cm de profundidade. Portanto, maiores profundidades atrasam o desenvolvimento de ambas as espécies, sendo uma importante informação para o manejo dessas plantas daninhas. campo casualizado repetições 4 0,5 05 0 5 (0,5 10 1 2,0 20 2 40 80 8 8, 120 12 12, 100%, 100 (100% 70 70% 50 30 . solar) Avaliouse Avaliou altura avaliadas S 1, Portanto 0, (0, 2, 100% (100 7 3 (0 (10 ( (1

ABSTRACT Understanding weed emergence and development aspects is essential in decision-making for management strategies. The study evaluated the effects of different sowing depths and light intensities on the emergence and development of the weeds Sida rhombifolia and Senna obtusifolia under field conditions. Each species constituted an experiment, and the experimental design used was completely randomized, with four replications. The treatments were arranged in a 6 x 4 factorial scheme, with the first factor corresponding to the six sowing depths (0.5; 1.0; 2.0; 4.0; 8.0, and 12.0 cm) and the second at four light intensities (100%, 70%, 50%, and 30% of sunlight). The seedling emergence was evaluated daily to obtain the emergence and emergence speed index. The height, time to floral induction, and dry matter of plants at flowering were also evaluated. When submitted to different levels of shading, S. rhombifolia seedlings emerge up to 12.0 cm deep. S. obtusifolia seedlings emerge at all sowing depths, even when subjected to different solar radiation intensities. Seedlings of S. rhombifolia and S. obtusifolia emerge less and slower in sowings between 8.0 and 12.0 cm depth and develop better under full sunlight in sowings between 1.0 and 4.0 cm depth. Therefore, greater depths delay the development of both species, which is important information for managing these weeds. decisionmaking decision making strategies conditions experiment randomized replications scheme 0.5 05 0 5 (0.5 10 1 2.0 20 2 40 80 8 120 12 12. 100%, 100 (100% 70 70% 50 50% 30 sunlight. . sunlight) index height induction shading S deep 8. 1. 4. Therefore 0. (0. 2. 100% (100 7 3 (0 (10 ( (1

RESUMEN: Aun siendo considerado un sistema de cultivo moderno, los sistemas silvopastoriles pueden degradarse rápidamente si no se observan algunos cuidados, principalmente, relacionados con el control de malezas, en las primeras etapas de establecimiento de este sistema. El presente trabajo tuvo como objetivo evaluar el efecto del aprovechamiento de leguminosas forrajeras en la supresión de malezas y en el desarrollo inicial de la Tectona grandis en la implementación de un sistema silvopastoril. Se utilizaron cuatro especies de leguminosas: Arachis pintoi, Stylosanthes guianensis, Vigna unguiculata y Cajanus cajan, que se compararon con tres regímenes de deshierbe: siega, desyerbado a mano y cero deshierbe (parcela sin deshierbe). El experimento se dispuso en un diseño de bloques completos al azar con cuatro repeticiones, y cada parcela experimental consistió en la longitud correspondiente a cuatro plantas teca por cuatro metros de ancho. Las evaluaciones de supresión de malezas se llevaron a cabo al final del período de crecimiento anual, representado por la temporada alta de lluvias en la región. Se identificaron, cuantificaron las especies de malezas y se determinó la materia seca de malezas producidas por las especies encontradas. El desarrollo de las plantas de teca se evaluó midiendo la altura de las plantas, el diámetro del tallo en el cuello de las plantas y en la altura del pecho en un período de dos años. El A. pintoi y los S. guianensis ejercen poca presión competitiva sobre las malezas, pero no interfieren en las variables de crecimiento de la T. grandis.

SUMMARY: Even when considered a modern cultivation system, silvopastoral systems can be rapidly degraded if some cares, mainly related to weed control, are not observed at the early stages of establishment of this system. The present work had the objective of evaluating the use of forage legumes on weed suppression and on the initial development of Teak (Tectona grandis) when implementing a silvopastoral system. Four legume species were used, namely: pinto peanut (Arachis pintoi), Brazilian stylos (Stylosanthes guianensis), cowpea (Vigna unguiculata) and pigeon pea (Cajanus cajan), which were compared with three weeding regimes: (i) mowing, (ii) hand weeding, and (iii) zero weeding (unweeded plot). The experiment was laid out in a randomized complete-block design with four replications. Each experimental plot consisted of the length corresponding to four Teak plants by four meters in width. Weed suppression assessments were carried out at the end of the annual growing period, represented by the high rainfall season in the region. Weed species were identified and quantified. The weed dry matter produced by found species was determined. Teak plants development was assessed by measuring plants height, stem diameter at the plants neck and breast height in a 2-year period. Pinto peanut and Brazilian stylos put little competitive pressure on weeds, although they produced the largest quantities of organic matter and available nitrogen in the soil and did not interfere in the growth variables of the teak component.

RESUMO Informações sobre o impacto dos herbicidas no solo baseado no crescimento de espécies bioindicadoras são extremamente úteis no desenvolvimento de estratégias de gerenciamento de culturas. O objetivo deste estudo foi avaliar o potencial de lixiviação do S-metolachlor em precipitações pluviométricas naturais em um Latossolo (Oxisol) de textura média, através do uso de plantas bioindicadoras. Adotou-se o delineamento experimental inteiramente casualizado, com quatro repetições e os tratamentos dispostos em esquema fatorial 3 × 8 [três índices de precipitação ocorrida no ambiente antes da coleta das amostras (50, 91 e 131 mm) e oito profundidades no perfil do solo (0-0,03; 0,03-0,06; 0,06-0,09; 0,09-0,12; 0,12-0,15; 0,15-0,20; 0,20-0,25; 0,25-0,30 m)]. Colunas de PVC foram introduzidas mantendo a integridade original do solo durante a amostragem, após o acúmulo de precipitação natural estipulado. As colunas foram separadas por seção longitudinal para a semeadura das espécies bioindicadoras (pepino, alface, capim-marmelada e sorgo). Os sintomas de fitotoxicidade nas plantas bioindicadoras foram avaliados adotando-se a escala visual de fitotoxicidade entre 0 e 100%, aos 5, 7, 9 e 11 dias após a semeadura. As respostas das espécies bioindicadoras ao efeito residual do S-metolachlor foram variáveis e dependeram da precipitação. Em um Latossolo de textura média, as maiores concentrações de S-metolachlor ocorrem em profundidades que variam entre 0 e 0,06 m. A profundidade máxima de lixiviação detectada foi de 0,12-0,15 m com 131 mm de precipitação. Por apresentar sintomas de fitotoxicidade em maiores profundidades, o pepino foi a espécie mais sensível à presença de S-metolachlor em Latossolo de textura média.

ABSTRACT Information about the impact of herbicides in the soil based on the growth of bioindicator species is extremely useful in developing crop management strategies. Therefore, this study aims to evaluate the leaching potential of the herbicide S-metolachlor under different natural precipitations in medium-textured Oxisol using bioindicator plants. A completely randomized experimental design was adopted, with four replicates and treatments arranged in a 3 × 8 factorial scheme [three indexes of precipitation occurred in the environment before the collection of the samples (50, 91, and 131 mm) and eight depths in the soil profile (0-0.03; 0.03-0.06; 0.06-0.09; 0.09-0.12; 0.12-0.15; 0.15-0.20; 0.20-0.25; 0.25-0.30 m)]. PVC columns were used, maintaining the original soil integrity during sampling after accumulating the stipulated natural precipitation. Longitudinal sections separated the columns to sow the bioindicator species (cucumber, lettuce, Alexander grass, and sorghum). The phytotoxicity symptoms of bioindicator plants were evaluated, adopting a phytotoxicity visual scale between 0 and 100%, at 5, 7, 9, and 11 days after seeding. The responses of the bioindicator species to the residual effect of the herbicide S-metolachlor were variable and depended on the rainfall level. Generally, in a medium-textured Oxisol, the higher values of concentration of S-metolachlor occurs in depths ranging between 0 and 0.06 m. The maximum leaching depth detected was 0.12-0.15 m with 131 mm of precipitation. Cucumber was the most sensitive species to the presence of S-metolachlor in an Oxisol of medium-texture since it presents symptoms of phytotoxicity at higher depths.

RESUMO A presença de plantas daninhas como consequência da degradação de pastagens é um dos principais problemas da pecuária em todo o mundo. Assim, o conhecimento dos aspectos de interferência e do período apropriado para o manejo dessas espécies é essencial para a decisão de aplicar uma determinada medida de controle. Este estudo teve como objetivo estudar a interferência de plantas daninhas sobre os componentes morfoestruturais e na qualidade nutricional do capim Marandu em condições de renovação ou manutenção de pastagem. Os experimentos foram conduzidos em delineamento experimental de blocos ao acaso, com quatro repetições, sendo os tratamentos constituídos por oito períodos crescentes de convivência entre o capim Marandu e as plantas daninhas (0, 15, 30, 45, 60, 75, 90, e 120 dias). A caracterização da gramínea forrageira foi realizada ao final do período de condução do experimento, que correspondeu a 120 dias de convivência, obtendo os principais componentes morfoestruturais e nutricionais da forragem. As plantas daninhas interferem na qualidade morfoestrutural e nutricional de áreas de pastagem com capim Marandu que passam pelo processo de renovação ou manutenção. A digestibilidade in vitro da matéria orgânica do capim Marandu é negativamente influenciada pela presença de plantas daninhas, sugerindo que medidas de controle em áreas de renovação ou manutenção de pastagens devem ser adotadas até 24 e 18 dias de convivência em comum, respectivamente.

ABSTRACT The presence of weeds as a consequence of pasture degradation is one of the main problems facing livestock worldwide. Thus, knowing the interference aspects and the appropriate time for weed management is essential for applying a particular control measure. This research aimed to study the weed interference on the morphostructural and nutritional quality of the Marandu palisade grass in conditions of renewal or maintenance of pasture. The experiments were conducted in a randomized block design, with four replicates and treatments consisted of eight growth periods of coexistence between Marandu palisade grass and weeds (0, 15, 30, 45, 60, 75, 90, and 120 days). Forage grass was characterized at the end of the experimental period, corresponding to 120 days of coexistence, and the main morphostructural and nutritional components were determined. Under the renewal or maintenance process, the weeds interfere in the morphostructural and nutritional quality of pasture areas with Marandu palisade grass. In vitro organic matter digestibility of Marandu palisade grass is negatively influenced by weeds, suggesting that control measures for renewal or maintenance areas should be adopted within 24 and 18 days of coexistence, respectively.

ABSTRACT The presence of weeds in silvicultural systems has been considered one of the main obstacles to the success of projects designed to recover degraded areas. The aim of this study was to evaluate the selectivity of herbicides applied at post-emergence in the initial growth of seedlings of capixingui (Croton floribundus), açoita-cavalo (Luehea divaricata), and guaritá (Astronium graveolens), in the municipalities of Jaboticabal and Junqueirópolis, state of São Paulo. The experimental design was completely randomized, with four replications, and the treatments consisted of herbicides (g a.i.·ha–1) clethodim + phenoxaprop-p-ethyl (50 + 50), sethoxydim (184), quizalofop-p-ethyl (75), nicosulfuron (50), fluazifop-p-butyl (125), fomesafen (225), haloxyfop-methyl (48), bentazon (720), chlorimuron-ethyl (15), in addition to control without herbicide. The characteristics analyzed were: plant height increase and visual phytointoxication at 7, 14, 21, 28, 35, and 42 days after herbicide application. At the end of the experiment, the shoots of the plants were removed to assess shoot dry matter. The herbicides clethodim + fenoxaprop-p-ethyl, fluazifop-p-butyl, and quizalofop-p-ethyl showed selective potential for the species capixingui, açoita-cavalo, and guaritá. The herbicide chlorimuron-ethyl caused mild intoxication symptoms when applied to seedlings of capixingui and açoita-cavalo; also, it was not selective for the guaritá species grown in Jaboticabal. All species showed selectivity to the herbicides sethoxydim, fomesafen, haloxyfop-methyl, and nicosulfuron, as their growth and initial development were not influenced. The herbicide bentazon caused high percentages of injury to açoita-cavalo plants in both cultivation places, but it did not influence the growth and development of the species.

RESUMO As plantas daninhas são um dos fatores ecológicos que afetam diretamente no custo da produção agrícola. Assim, compreender os aspectos de emergência e desenvolvimento dessas espécies é essencial na tomada de decisão para estratégias de seu manejo. Objetivouse avaliar, em condições de campo, o efeito de diferentes profundidades de semeadura e de diversas intensidades luminosas na emergência e no desenvolvimento das plantas daninhas Acanthospermum australe (Loefl.) Kuntze e Ipomoea grandifolia (Dammer) O’Donell. Cada espécie constituiu um experimento e o delineamento experimental utilizado foi o inteiramente casualizado, com quatro repetições. Os tratamentos foram dispostos em esquema fatorial 6 x 4, seis profundidades de semeadura (0,5; 1,0; 2,0; 4,0; 8,0 e 12,0 cm) associadas a quatro intensidades luminosas (100%, 70%, 50% e 30% da luz solar) obtidas por meio de sombrites. Avaliou-se diariamente a emergência das plântulas para obtenção da emergência e do índice de velocidade de emergência. A altura/comprimento das plantas, o tempo até a indução floral e a matéria seca das plantas no florescimento também foram avaliadas. As plantas de A. australe e I. grandifolia emergem sob intensidades luminosas de 100, 70, 50 e 30% de radiação solar e, em semeaduras de até 12,0 cm de profundidade. No entanto, a espécie A. australe é a única afetada pela intensidade luminosa, profundidade de semeadura e pela interação destes dois fatores em todas as avaliações realizadas. A redução das intensidades luminosas acarreta menor desenvolvimento de plantas de I. grandifolia.

ABSTRACT Weeds are one of the ecological factors that directly affect agricultural costs. Thus, understanding the emergence and development of these species is essential for the decision-making on weed control strategies. This study aims to evaluate the effect of different sowing depths and luminous intensities under field conditions on the emergence and development of the Acanthospermum australe (Loefl.) Kuntze and Ipomoea grandifolia (Dammer) O’Donell. Each species constituted one experiment, and the completely randomized design with four repetitions was adopted. The treatments were arranged in a 6 x 4 factorial scheme, with six sowing depths (0.5; 1.0; 2.0; 4.0; 8.0; and 12.0 cm) associated with four luminous intensities (100%, 70%, 50%, and 30% sunlight) obtained using shade cloths. The emergence of seedlings was evaluated daily to obtain the emergence and the emergence speed index. Plant height(length), the period until flower induction, and the dry matter of plants during flowering were also analyzed. A. australe and I. grandifolia emerge under the luminous intensities of 100, 70, 50, and 30% of solar radiation and in sowings depths up to 12.0 cm. Nevertheless, A. australe is the only one affected by luminous intensity, sowing depth, and the interaction between both factors in all the analyzes conducted. Luminous intensity reduction leads to lower development of I. grandifolia.

ABSTRACT Auxin-based herbicides, such as 2,4-dichlorophenoxyacetic acid (2,4-D), are lethal to plants at higher doses, but can enhance plant growth at nontoxic concentrations. The stimulating effect of low doses of a substance considered toxic is known as hormesis. This study used dose-response curves to assess the hormesis effect of low doses of 2,4-D choline salt herbicide on soybean (Glycine max (L.) Merr.) biometric variables with distinct growth habits at different phenological stages. A completely randomized experimental design with seven replicates was used, and the treatments consisted of six fractions of the average dose indicated on the label of 2,4-D choline salt formulation: 0 (control), 0.068, 0.684, 6.84, 68.4 and 684 g ae ha-1 applied at the plant’s phenological stages second node with fully developed leaves (V2) or fifth node with fully developed leaves (V5). The plants were assessed for their main biometric parameters. The results were analyzed by ANOVA and, when significant, the hormesis model was tested. The maximum effect of hormesis on the main biometric parameters of soybean plants was estimated for doses between 0.20 and 36.01 g ae ha-1 of the herbicide and varies depending on the evaluated phenological stage of the plants. Low doses of 2,4-D choline salt herbicide may increase shoots, roots and total DM when applied at stages V2 and V5 of soybean with determinate growth habit and V2 of indeterminate growth habit. There was no adjustment of the hormesis model for the soybean plant with indeterminate growth habit at stage V5.

RESUMO Operações sucessivas de corte são os principais custos na manutenção de gramados. O dispêndio com os cortes leva à busca por alternativas para o manejo mecânico. O presente estudo teve por objetivo estudar os efeitos de doses do herbicida imazapic aplicado isolado ou em associação com imazapyr, como regulador de crescimento das gramas Tifton 419 e Esmeralda. Adotou-se o delineamento experimental de blocos casualizados, com quatro repetições e os tratamentos constituíram de quatro doses do herbicida imazapic isolado (35; 70; 105 e 140 g i.a. ha-1) e três doses da associação de imazapic + imazapyr (7,875 + 2,625; 15,57 + 5,25 e 23,625 + 7,875 g i.a. ha-1) em duas aplicações sequenciais para ambas as espécies. Avaliaram-se os sintomas visuais de injúria, a altura do dossel, a altura e o número de inflorescências e a matéria seca total das aparas. As aplicações de imazapic isolado ou em associação com imazapyr foram efetivas na redução de todas as variáveis morfológicas da grama Tifton 419. O imazapic aplicado isolado ou associado ao imazapyr proporcionou controle satisfatório do crescimento e da quantidade de matéria seca das aparas da grama Esmeralda, no entanto, algumas doses desse herbicida aumentaram o número de inflorescências presentes nos gramados.

ABSTRACT Successive mowings are the major maintenance cost of lawns. These costs have led to the search for alternatives to mechanical management. This study aimed to determine the effects of imazapic herbicide doses applied alone or combined with imazapyr as a growth regulator of Tifton 419 and Zoysia grasses. The experimental design was randomized blocks with four replicates, and the treatments consisted of four doses of herbicide imazapic applied alone (35; 70; 105 and 140 g a.i. ha-1) and three doses of imazapic + imazapyr mixture (7.875 + 2.625; 15.57 + 5.25 and 23.625 + 7.875 g a.i. ha-1) in two sequential applications on both grass lawns. Visible injury symptoms, canopy height, height and number of inflorescences, and total dry matter of clippings were determined. Applications of imazapic alone or combined with imazapyr effectively reduced all morphological variables of Tifton 419 grass. Imazapic applied alone or mixed with imazapyr provided adequate control of growth and quantity of dry matter of Zoysia grass clippings. Still, with some application doses of this herbicide, the number of inflorescences present in the lawns increased.

Abstract Background: Weeds are one of the ecological factors that affect the agricultural economy permanently. Thus, understanding the weed emergence and development is essential in decision making for management strategies. Objective: This study aimed to evaluate the effect of different sowing depths and light intensities on the emergence and development of the weed species Euphorbia heterophylla and Desmodium tortuosum under field conditions. Methods: Each species consisted of an experiment carried out in a completely randomized design with four replications. Treatments were arranged in a 6 × 4 factorial scheme, with six sowing depths (0.5, 1.0, 2.0, 4.0, 8.0, and 12.0 cm) associated with four light intensities (100, 70, 50, and 30% of the solar light intensity) obtained with shading screens. Seedling emergence capacity was evaluated daily to obtain the percentage of emergence and the emergence rate index (ERI). Plant height, time to floral induction, plant dry matter during flowering were also evaluated. Results: Seedlings of E. heterophylla emerged under all solar radiation conditions and sowing up to 12.0 cm deep, while seedlings of D. tortuosum showed no emergence only at 12.0 cm deep with light intensities below 70%. The 100% solar radiation condition provided higher total and daily dry matter accumulation in E. heterophylla plants, while D. tortuosum plants showed higher values for both variables under 70 and 50% incidence of solar radiation. Conclusions: The full sunlight condition provided the best development of E. heterophylla plants. Different levels of lightness and sowing depths interfere the emergence and the development of D. tortuosum plants.

RESUMO O déficit hídrico é um fator limitante, pois desencadeiam diferentes adaptações fisiológicas e anatômicas que tem efeitos deletérios nas plantas o que pode afetar a seletividade dos herbicidas e ocasionar perdas às culturas agrícolas. O objetivo deste trabalho foi avaliar a ação do herbicida chlorimuron-ethyl, pulverizado em diferentes estádios de desenvolvimento da soja, cultivar convencional e transgênica, sob diferentes manejos de água no solo. A dose de 20 g i.a. ha-1 do herbicida chlorimuron-ethyl foi aplicada em dois estádios fenológico (V2-primeiro trifólio aberto e V4-terceiro trifólio aberto) de duas cultivares de soja: MG/BR 46 Conquista (convencional) e BRS Valiosa (RR), sob três condições hídricas no solo (-0,03; -0,07 e -0,5 MPa). Avaliou-se a fitointoxicação e altura de plantas aos 3, 7, 14 e 21 dias após a aplicação do herbicida. Ao final do estudo, determinou-se a massa seca da parte aérea, massa seca das raízes e nodulação do sistema radicular por meio do número e massa seca de nódulos. Constatou-se que, em condição de déficit hídrico as plantas de soja apresentaram uma menor fitotoxicidade visual quando submetida à pulverização do herbicida chlorimuron-ethyl. Além disso, o uso do herbicida chlorimuron-ethyl reduziu o crescimento e a biomassa das plantas de soja, afetando também a nodulação da cultura. A cultivar transgênica BRS Valiosa RR mostrou um melhor desempenho quando submetida a uma condição de escassez hídrica moderada (-0,07 MPa) para sustentar a fixação biológica de nitrogênio.

ABSTRACT Water deficit is a limiting factor for the soybean yield; it triggers different physiological and anatomical adaptations that have deleterious effects on the plants and can affect the selectivity of herbicides, causing production losses. In this context, the objective of this work was to evaluate the action of the chlorimuron-ethyl herbicide when applied at different stages of soybean plants, using conventional and transgenic cultivars, and different soil water potentials. A rate of 20 g ha-1 of the chlorimuron-ethyl herbicide was applied to two soybean cultivars (MG/BR46-Conquista - conventional, and BRS-Valiosa-RR - transgenic) at two phenological stages (V2 - first fully expanded trifoliate leaves, and V4 - third fully expanded trifoliate leaves), using three soil water potentials (-0.03 MPa, -0.07 MPa, and -0.5 MPa). Phytotoxicity, and plant height were evaluated at 3, 7, 14, and 21 days after the herbicide application. The shoot dry weight, root dry weight, and root system nodulation were evaluated. The soybean plants had lower phytotoxicity when subjected to application of chlorimuron-ethyl under water deficit conditions. The use of chlorimuron-ethyl reduced the growth and biomass of soybean plants and affected the plants' root system nodulation. The transgenic cultivar (BRS-Valiosa-RR) presented better performance when subjected to a moderate water deficit (-0.07 MPa), which contributes to biological nitrogen fixation.

RESUMO: O solo é o destino final da maioria dos herbicidas utilizados no sistema agrícola e, sendo esta relação dinâmica, eles podem permanecer na solução ou ser carregados no perfil do solo, podendo atingir o lençol freático. O objetivo deste trabalho foi avaliar o potencial de lixiviação do herbicida tebuthiuron por meio de plantas bioindicadoras e após a ocorrência de precipitações pluviométricas naturais, em solos com texturas franco arenoso (Latossolo Vermelho-Amarelo) e argiloso (Neossolo Litólico). O delineamento experimental foi o inteiramente casualizado em um esquema fatorial 3 x 8 com quatro repetições, sendo três níveis de precipitação pluviométrica (30-40, 60-80 e 100-120 mm) e oito de profundidade do perfil do solo (0-3, 3-6, 6-9, 9-12, 12-15, 15-20, 20-25 e 25-30 cm). As coletas das amostras ocorreram após a aplicação do herbicida tebuthiuron nas doses de 750 e 600 g ha-1 para o solo argiloso e arenoso, respectivamente, e posterior acúmulo das precipitações. Para a coleta das amostras foram introduzidas, no perfil do solo, colunas de PVC com 30 cm de altura e 15 cm de diâmetro. As colunas foram retiradas cuidadosamente escavando-se ao seu redor, mantendo a integridade original do solo durante a coleta. Posteriormente, as colunas foram separadas com corte longitudinal, para a semeadura das espécies bioindicadoras pepino (Cucumis sativus L.) e alface (Lactuca sativa L.). Para as avaliações das plantas bioindicadoras nas colunas, adotou-se a escala de notas de 0 a 100% de fitotoxicidade, aos 5, 7, 10 e 12 dias após a semeadura. A mobilidade do herbicida tebuthiuron mostrou-se reduzida em ambos os tipos de solo estudado, independentemente da precipitação pluvial, e as plantas de pepino mostraram-se mais adequadas para serem utilizadas como espécie bioindicadora.

ABSTRACT: The last destination of most herbicides used in agricultural systems is the soil. This is a dynamic interaction; herbicides can remain in the soil solution or be carried through the soil profile, reaching the water table. The objective of this work was to evaluate the leaching potential of the tebuthiuron herbicide using bioindicator plants grown in an Oxisol of sandy loam texture and in an Entisol of clay texture, after the occurrence of natural rainfall events. A complete randomized experimental design was used, in a 3×8 factorial arrangement, with four replications. The treatments consisted of three accumulated natural rainfall depths (30-40, 60-80, and 100-120 mm) and eight soil profile layers (0-3, 3-6, 6-9, 9-12, 12-15, 15-20, 20-25, and 25-30 cm). Soil samples were collected after the tebuthiuron herbicide application - 750 for clayey soil, and 600 g ha-1 for the sandy loam soil -and the rainfall events. PVC pipes with length of 30 cm and diameter of 15 cm were introduced into the soil profile for sampling. The pipes with soil columns were carefully removed by digging around them, to maintain the soil original integrity during collection and, subsequently, cut longitudinally for sowing the bioindicator species - cucumber (Cucumis sativus L.), and lettuce (Lactuca sativa L.). Then, the phytotoxicity in the bioindicator plants grown in these soils were evaluated at 5, 7, 10, and 12 days after sowing, using a grading scale of 0 to 100%. The mobility of the tebuthiuron herbicide was low in both soils, regardless of the rainfall depth, and the cucumber was the most suitable plant species to use as a bioindicator.

RESUMO A utilização de espaçamento de fileira dupla na cultura da soja é recente e constituem-se em uma nova tecnologia de produção de soja no Brasil e no mundo, com isso, a interferência de plantas daninhas pode ser diferentes em relação ao cultivo de linhas simples. Assim, o objetivo deste trabalho foi avaliar a interferência de plantas daninhas na cultura da soja em função do espaçamento de semeadura. O delineamento experimental utilizado foi em blocos casualizados e os tratamentos foram dispostos em esquema fatorial (2x16): dois espaçamentos, um espaçamento de fileira dupla [(0,20 x 0,20 m) x 0,67 m] e um espaçamento convencional de fileira simples (0,45 x 0,45 m) e dezesseis períodos de manejo de plantas daninhas, sendo oito períodos de controle em que a soja foi mantida livre das plantas daninhas por períodos crescentes de 7; 14; 21; 28; 35; 42; 49 e 145 dias após a sua emergência e oito períodos de convivência, quando a cultura foi mantida na presença da comunidade infestante pelos mesmos períodos. O Período Anterior a Interferência foi menor no espaçamento em fileira dupla (8 dias) quando comparado ao espaçamento simples (18 dias). O Período Total de Prevenção da Interferência foi de 36 e 31 dias para o espaçamento em fileira dupla e simples, respectivamente, sendo que a emergência de plantas daninhas após este período não reduziu a produtividade, porém o Período Crítico de Prevenção à Interferência foi maior no espaçamento em fileira dupla (28 dias) em comparação ao da fileira simples que foi de 13 dias. O espaçamento em fileira dupla apresentou uma produtividade de grãos superior ao de fileira simples.

ABSTRACT The use of double row spacing on soybean crop is recent and consists of a new soybean production technology in Brazil and worldwide, so weed interference may be different in relation to single crop row. Thus, the objective of this work was to evaluate the weed interference in soybean crop in function of sowing spacing. The experimental design was randomized blocks and treatments were arranged in a factorial (2x16): two spacings, a double row spacing [(0.20 x 0.20 m) x 0.67 m] and a conventional single row spacing (0.45 x 0.45 m) and sixteen periods of weed management, being eight control periods in which soybean was kept free of weeds by increasing periods of 7; 14; 21; 28; 35; 42; 49 and 145 days after emergence and eight coexistence periods, when the crop was maintained in the presence of the weed community for the same periods. The Critical Timing of Weed Removal (CTWR) was lower in the double row spacing, with eight days, compared with single spacing that was of 18 days. The Critical Weed-Free Period (CWFP) was of 36 and 31 days for double and single row spacing, respectively, and the emergence of weeds after this period did not cause damage to the productivity, but the Critical Period of Weed Control (CPWC) was higher in double row spacing (28 days) compared to the single row, which was of 13 days. The spacing in double row had a higher grain yield than the spacing in single row.

Resumen En un latosol localizado en Sinop, Mato Grosso, Brasil se evaluaron los efectos de la infestación de las principales malezas de la zona (Hyptis suaveolens, Senna obtusifolia y Sida rhombifolia), en diferentes edades después de la siembra, en la producción y algunas características morfogénicas de la gramínea forrajera Brachiaria brizantha (ahora: Urochloa brizantha) cv. Marandu. Los tratamientos fueron dispuestos en un delineamiento experimental de bloques al azar con 4 repeticiones y consistieron en los períodos de convivencia: 0, 15, 30, 45, 60, 75, 90 y 120 días después de la emergencia de la gramínea. Al finalizar cada uno de estos períodos se realizó una evaluación fitosociológica de la comunidad infestante y se eliminaron las malezas utilizando un herbicida. Al término del período experimental se evaluaron los principales parámetros morfogénicos del pasto, así como la producción de materia seca. Los resultados mostraron un efecto negativo de las malezas en la altura de planta y el número de rebrotes, así como en la producción de materia seca de hojas y tallos. La presencia de las malezas redujo la producción del pasto en todos los tratamientos, variando de 50% (competencia durante los primeros 15 días) hasta 74% (120 días). Por tanto las medidas de control de las malezas deben ser adoptadas durante las 2 primeras semanas de convivencia con el pasto Marandu.

Abstract The present study evaluated the effects of different periods of coexistence among the main weeds and Marandu brachiaria grass (Brachiaria brizantha, now Urochloa brizantha) in newly sown pasture. The experiment was conducted in a randomized block with 4 replications, with treatments being 8 coexistence periods: 0, 15, 30, 45, 60, 75, 90 and 120 days after emergence. A phytosociological assessment of the weed community was carried out at the end of the coexistence periods, and weeds were eliminated from the appropriate treatment using herbicide. Key morphogenic parameters of the forages were assessed at the end of the experimental period and dry matter production was determined. Results indicated that the presence of weeds had negative impacts on the main morphogenic components, such as plant height, number of tillers and production of leaf and stem dry matter. The presence of weeds reduced productivity in Marandu, with 15 days competition being sufficient to reduce forage production by approximately 50%, suggesting that weed control measures should be adopted within 15 days following emergence of seedlings of Marandu and weeds.

RESUMO O comportamento invasivo do picão-preto (Bidens pilosa L.) em áreas de cultivo se deve à sua adaptação ecológica e regeneração agressiva, alicerçada na germinação das sementes. Objetivou-se, com a presente pesquisa, conhecer o efeito de diferentes procedências e temperaturas na germinação de sementes de B. pilosa. As sementes foram coletadas em Entre Rios do Oeste, PR, Botucatu, SP, Capão Bonito, SP, São Joaquim da Barra, SP, Sertãozinho, SP, Selvíria, MS, Barra do Garças, MT, Areia, PB e Manaus, AM e avaliadas quanto ao teor de água, massa de 1000 sementes, índice de velocidade de germinação e germinação conduzida a 10, 15, 20, 25, 30, 35, 40 e 45 ºC e avaliada aos 60 dias. O delineamento experimental adotado foi o inteiramente casualizado em esquema fatorial 9 x 8 (procedências x temperaturas) com quatro repetições e as médias foram comparadas pelo teste de Scott-Knott. A germinação, o vigor e a massa de sementes de B. pilosa dependem do local de procedência. Temperaturas superiores a 35 °C são letais às sementes. A temperatura de 15 ºC permite a máxima germinação das sementes em menor tempo da quase totalidade das procedências.

ABSTRACT The invasive behavior of beggarticks (Bidens pilosa L.) in cropped areas is due to its ecological adaptation and aggressive regeneration, which is dependent on seed germination. The objective of this research was to verify the effects of B. pilosa seed origin and temperature on seed germination. The seeds were collected in Entre Rios do Oeste, PR, Botucatu, SP, Capão Bonito, SP, São Joaquim da Barra, SP, Sertãozinho, SP, Selvíria, MS, Barra do Garças, MT, Areia, PB and Manaus, AM. The seeds were evaluated regarding moisture content, 1000-seed weight, germination speed index and germination at 60 days (normal seedlings, dormant seeds and dead seeds) at the temperatures of 10, 15, 20, 25, 30, 35, 40, and 45 ºC. The replicates were distributed according to a completely randomized design in a 9 x 8 factorial arrangement (seed origin x temperature) with four replicates. The means were compared by the Scott-Knott test. B. pilosa seeds germination depends on seed origin. Temperatures higher than 35 ºC are lethal to the seeds. The temperature of 15 ºC allows maximum germination in the shortest time whichever the seed origin.