WEED COMPOSITION IN AUTUMN-WINTER CROPS AND SOYBEAN IN SUCCESSION

Chemical management and the predecessor culture directly influence the occurrence of weeds in the agricultural system. The study aimed to evaluate weed infestation in autumn-winter crops and soybean in succession desiccated with glyphosate. The design used was randomized blocks, with plots measuring 3 x 5 m, with the following treatments: 1 (brachiaria); 2 (cowpea bean); 3 (corn intercropped with brachiaria), and 4 (corn). All areas were desiccated with 2 L ha-1 of glyphosate. The weed species community changed from winter cultivation to soybean cultivation. According to the predecessor crops, absolute infestation and weed composition are modified in soybean crops. Weed diversity in corn-brachiaria intercropping areas in winter was different concerning occurrence in the same area in summer in soybean cultivation. Brachiaria and corn grown intercropped with brachiaria have lower weed diversity in soybean in succession. The corn-brachiaria intercropping integrated with the use of glyphosate reduced weed diversity in soybean. There was only one weed species in the soybean crop in which there was a corn-brachiaria intercropping as a predecessor crop.O manejo químico e a cultura antecessora influenciam diretamente a ocorrência de plantas daninhas no sistema agrícola. Objetivou-se nesta pesquisa avaliar a infestação de plantas daninhas em culturas de outono-inverno e na soja em sucessão dessecadas com glyphosate. O delineamento utilizado foi em blocos casualizados, com parcelas medindo 3 x 5 m, com os seguintes tratamentos: 1 (brachiaria); 2 (feijão-caupi); 3 (consorcio milho com brachiaria) e 4 (milho). Todas as áreas foram dessecadas com 2 L ha-1 de glyphosate. A comunidade de espécies daninhas sofreu alterações do cultivo de inverno para o cultivo da soja. A infestação absoluta e a composição de plantas daninhas são modificadas na cultura da soja em função de culturas antecedentes. A diversidade de plantas daninhas nas áreas de consorcio milho-braquiária no inverno foi distinta em relação ocorrência na mesma área no verão no cultivo da soja. Braquiária e consorcio milho-braquiária apresentam menor diversidade de plantas daninhas na soja em sucessão. O consorcio milho-braquiária integrado ao uso do glifosato reduziu a diversidade de plantas daninhas na soja. Na cultura da soja em que havia como cultura antecessora consorcio milho-braquiária ocorreu apenas uma espécie de planta daninha

WEEDS IN SOYBEAN CROP AFTER ANNUAL CROPS AND PASTURE

The use of crop practices to reduce the weed community is an ally to integrated weed management. Given this, the study aimed to identify a composition and weed infestation in a soybean area under different predecessor crops implanted in different years. The experiment was carried out in the 2019/2020 harvest in Dourados, MS. The experimental design was a randomized block with nine treatments. The treatments were composed of autumn-winter crops. The area with predecessor cultivation: corn-Brachiaria intercropping; cowpea beans; single corn; an area with predecessor cultivation of Brachiaria as pasture for one year; two years; three years; four years; five years, and six years. All treatments were followed by soybean cultivation in the 2018/2019 harvest and an intercropping with corn and Brachiaria in the 2019 off-season harvest. There was a difference in the absolute weed infestation between the evaluated areas. Treatments with corn and cowpea had greater weed infestation. However, areas with pasture or intercropping with corn and Brachiaria showed less infestation, especially in areas with Brachiaria grown in the off-season for more than two years. The weed species composition differs between the areas evaluated. The implantation of a corn-Brachiaria intercropping in the off-season under a crop rotation system, especially in areas with Brachiaria grown in the off-season for more than four years, reduces the weed infestation

Efeito do sistema de cultivo e manejo do solo no estabelecimento de soja em terras baixas/ Effect of the growing and soil management system on soybean establishment

Objetivou-se com o trabalho avaliar a resposta das plantas da soja implantada em diferentes sistemas de cultivo e manejo do solo, no estabelecimento da cultura em terras baixas de clima temperado. Quatro tratamentos de manejo de solo foram avaliados em condições de terras baixas, em áreas de arroz, para implantação da cultura da soja: camalhão escarificado (CE), onde implantou-se a soja no sistema sulco-camalhão construído em solo previamente escarificado; sulco-camalhão (C), com plantio de soja em camalhão construído em solo não escarificado; escarificado (E) com plantio de soja em solo escarificado mas sem sulco-camalhões; e convencional (Convencional), com plantio de soja em sistema usual, sem camalhão ou escarificação do solo. Foram avaliados a área foliar, altura, diâmetro do caule e conteúdo de água das plantas. As avaliações foram efetuadas quinzenalmente da emergência à maturação dos grãos. A utilização de camalhão e escarificação favorecem o crescimento e desenvolvimento da planta, diminuindo o estresse causado pelo encharcamento do solo e permitindo melhor ambiente para o desenvolvimento do sistema radicular das plantas

Efeito da época de preparo do camalhão no desenvolvimento de plantas de soja em terras baixas/ Effect of the time of preparing the camalhão on the development of soybean plants

Objetivou-se com o presente estudo avaliar o estabelecimento e o desempenho de crescimento de plantas de soja, quando cultivadas em sistema de sulco-camalhão, preparado antecipadamente ou na hora da semeadura, em terras baixas de clima temperado. O experimento foi conduzido a campo, na área experimental da Embrapa Clima Temperado, Estação Experimental Terras Baixas, no município do Capão do Leão-RS, em delineamento experimental em blocos casualizados, com parcelas dispostas em faixas, com seis repetições. Os tratamentos constaram da época de preparo do camalhão. Os camalhões antecipados (tratamento 1 - TCA), foram construídos em abril de 2018, com camalhoeira, sendo imediatamente semeado a lanço o azevém cv. BRS Ponteio, na densidade de 15 kg ha?1 de sementes. Previamente a semeadura da soja, a área foi dessecada com 1440 ge.a. ha?1 de glyphosate, e a semeadura foi realizada com semeadeira Vence Tudo. Os camalhões confeccionados concomitantemente ao plantio (tratamento 2 - TCFH), foram feitos pela própria semeadeira, que possuía pé de pato específicos para tal operação. Foram avaliadas a área foliar, diâmetro do caule, altura de planta e conteúdo de água das plantas de soja em função dos dias após emergência (DAE). As avaliações foram efetuadas quinzenalmente da emergência à maturação dos grãos. A soja semeada no camalhão feito concomitante à semeadura apresentou melhor desenvolvimento vegetativo, comparativamente ao plantio sobre sulco-camalhão antecipado, principalmente aumentando a área foliar e diâmetro de caule. Supõe-se que condições diferenciais de adensamento e fertilidade do solo e consequente desenvolvimento radicular possam ter contribuído para esse resultado, mas isso deve ser investigado em maiores detalhes futuramente para confirmar ou refutar esses resultados

Competitive ability of canola (Brassica napus var. oleifera) hybrids with black oat (Avena strigosa) in a subtropical environment

The objective of this study was to assess the competitive ability of canola (Brassica napus var. oleifera) hybrids in competition with black oat (Avena strigosa) in a subtropical environment. The experiments were conducted in a greenhouse where canola hybrids ‘Hyola 61,’ ‘Hyola 76,’ ‘Hyola 433,’ and ‘Hyola 571’ were tested individually for their competitive performance with black oat. The plant proportion between black oat and the canola hybrid was changed (100%:0%; 75%:25%; 50%:50%; 25%:75%; and 0%:100%) while keeping the total population of plants constant (20 plants plot‑1). Photosynthesis rate (μmol m-2 s-1), internal CO2 concentration (μmol mol-1), and transpiration rate (mol H2O m-2 s-1) were assessed using an infrared gas analyzer 55 days after emergence. Leaf area (m2 m-2) and dry matter (g m-2) were also assessed on the same day. The data set was analyzed by the replacement series method for competition studies. There was evidence of intense competition between canola and black oat, independent of plant proportion. The competitive ability of canola was distinct among hybrids; Hyola 571 performed better than the others in the competition against black oat. Choosing the most competitive hybrid, such as Hyola 571, helps maintain high canola grain yield levels in areas infested with black oat

Competitive ability of bean cultivars with Urochloa plantaginea

The objective of this work was to evaluate the competitive ability of carioca bean cultivars BRS FC104, BRS FC402, IAC Imperador, IAC Milênio, IPR Tangará, and SCS Riqueza in the presence of Alexandergrass (Urochloa plantaginea) in different proportions of plants in association. The experiments were carried out in a greenhouse in a completely randomized design with four replications. The treatments were arranged according to the proportions of beans and Alexandergrass plants: 100:0, 75:25, 50:50, 25:75, and 0:100 or 40:00, 30:10, 20:20, 10:30, and 0:40 plants per pot. The competitiveness of the species was analyzed using diagrams applied to replacement experiments and also through relative competitiveness indices. At 30 days after crop emergence, leaf area (LA), height (HP), diameter (DP), and shoot dry mass (SM) of the plant shoots were measured, as well as variables related to the physiology of the species. There was competition among carioca bean cultivars in the presence of Alexandergrass regardless of the proportion of plants, causing decreases in DP, LA and SM. Basically, there is competition for the same environmental resources between beans and Alexandergrass. Highlights: There is competition between bean and Alexandergrass, for the same environmental resources; There is varietal difference - IAC Imperador and SCS 205 Riqueza are the most competitive ones; The escape to competition is the best approach to guarantee yield in Alexandergrass-infested fields.The objective of this work was to evaluate the competitive ability of carioca bean cultivars BRS FC104, BRS FC402, IAC Imperador, IAC Milênio, IPR Tangará, and SCS Riqueza in the presence of Alexandergrass (Urochloa plantaginea) in different proportions of plants in association. The experiments were carried out in a greenhouse in a completely randomized design with four replications. The treatments were arranged according to the proportions of beans and Alexandergrass plants: 100:0, 75:25, 50:50, 25:75, and 0:100 or 40:00, 30:10, 20:20, 10:30, and 0:40 plants per pot. The competitiveness of the species was analyzed using diagrams applied to replacement experiments and also through relative competitiveness indices. At 30 days after crop emergence, leaf area (LA), height (HP), diameter (DP), and shoot dry mass (SM) of the plant shoots were measured, as well as variables related to the physiology of the species. There was competition among carioca bean cultivars in the presence of Alexandergrass regardless of the proportion of plants, causing decreases in DP, LA and SM. Basically, there is competition for the same environmental resources between beans and Alexandergrass. Highlights: There is competition between bean and Alexandergrass, for the same environmental resources; There is varietal difference - IAC Imperador and SCS 205 Riqueza are the most competitive ones; The escape to competition is the best approach to guarantee yield in Alexandergrass-infested fields