Identifying the competitive ability of corn hybrids and the economic injury level (EIL) caused by Urochloa plantaginea is important for the adoption of integrated management of this weed. This work aims to evaluate the interference and EIL of U. plantaginea infesting corn hybrids. Treatments included the corn hybrids Syngenta Status VIP3, Syngenta SX8394 VIP3, Pioneer P1630H, Pioneer 30F53 YH, and Dow 135021, as well as 12 densities of U. plantaginea for each hybrid. We used a rectangular hyperbolic model to describe the relationship between corn grain productivity loss and the explanatory variables — plant density (PD), dry mass (DM) of the aerial parts, ground cover (GC), and leaf area (LA). EIL was determined using grain productivity, control cost, corn price, and herbicide efficacy. The rectangular hyperbolic model provides a satisfactory estimate of grain productivity loss regarding the interference of U. plantaginea in corn culture. The hybrids Pioneer 30F53 YH and Pioneer P1630H presented better competitiveness and higher EIL. Sowing the hybrids Pioneer P1630H, Pioneer 30F53 YH, and Dow 135021 increased EIL, justifying the adoption of control measures for U. plantaginea at higher densities.
This work is related to the project of Scientific Initiation of the second author. Universidade Federal da Fronteira Sul 1,
Para contornar os casos de plantas daninhas resistentes ao glyphosate torna-se necessário o uso de herbicidas com outros mecanizamos de ação. Objetivou-se com o trabalho avaliar a eficácia e a seletividade de herbicidas aplicados isolados ou em mistura de tanque para o manejo de plantas daninhas infestante da soja resistente ao glyphosate. Os tratamentos foram aplicados de forma sequencial, em pré-emergência: clomazone (900 g ha-1 i.a.); flumioxazin (50 g ha-1 i.a.); diclosulam (35,02 g ha-1 i.a.); s-metolachlor (1152 g ha-1 i.a.); sulfometuron + chlorimuron-ethyl (18,75 + 18,75 g ha-1 i.a.); pendimethalin (1250 g ha-1 i.a.); sulfentrazone (250 g ha-1 i.a.); sulfentrazone + chlorimuron-ethyl (250 + 20 g ha-1 i.a.); imazethapyr + sulfentrazone (100 + 250 g ha-1 i.a.) e imazaquin (150 g ha-1 i.a.) e em pós-emergência sobre esses mesmos tratamentos usou-se o glyphosate (1080 g ha-1 e.a.). Em pós-emergência aplicou-se de modo isolado o glyphosate (1080 g ha-1 e.a.) e misturados ao tanque do pulverizador com glyphosate (1080 g ha-1 e.a.), imazethapyr (100 g ha-1 i.a.), clethodim (96 g ha-1 i.a.) e chlorimuron-ethyl (20 g ha-1 i.a.), mais as testemunhas infestada e capinada. A área experimental estava infestada com uma porcentagem de 75% de plantas de papuã (Urochloa plantaginea) e 25% com plantas de milhã (Digitaria ciliaris), nas densidades médias de 133 e 45 plantas m-2, respectivamente. Aos 14 e 21 dias após a aplicação dos tratamentos (DAT) a aplicação de glyphosate + [sulfometuron + chlorimuron-ethyl] ocasionou fitotoxicidade à soja de 67 e 62% respectivamente. Para o controle de milhã e papuã essa mesma mistura apresentou índice de 88% aos 21 DAT, sendo que o controle para os demais tratamentos ultrapassou os 91% em todas as épocas avaliadas. Todos os tratamentos avaliados ocasionaram controle das duas plantas daninhas maior que 91%, exceto o glyphosate + [sulfometuron + chlorimuron-ethyl]. As associações dos herbicidas ao glyphosate ocasionaram controle das plantas daninhas e foram seletivas a soja, com exceção do sulfometuron + chlorimuron-ethyl, que apresentou menor controle e elevada fitotoxicidade. Alguns herbicidas prejudicaram os componentes de rendimento da soja, porém somente a mistura de sulfometuron + chlorimuron-ethyl apresentou diminuição da produtividade de grãos.
-The objective of the study was to assess the relative competitive ability of canola hybrids in the presence of turnip (Raphanus sativus) and ryegrass (Lolium multiflorum) in different ratios of plants in the mixture. The experiments were conducted in a greenhouse, in a completely randomized design with four replications. Treatments were arranged in ratios of canola against turnip or ryegrass: 100:0, 75:25, 50:50, 25:75 and 0:100. Competitive analysis of the species was accomplished by means of diagrams usually applied to replacement series and also by the relative competitiveness indices. Fifty days after the emergence of the species, measurements of leaf area and shoot dry mass were performed. There was a competition between canola hybrids and weeds, with reduction for all variables. There was a differential competitive ability among canola hybrids in the presence of turnip and/or ryegrass. Canola hybrid Hyola 433 was more competitive in the presence of turnip than Hyola 61, 76 and 571 CL. Hyola 61, 76, 433 and 571 CL do not differ in terms of competition ability when growing with ryegrass.Keywords: Brassica napus, Raphanus sp., Lolium multiflorum. RESUMO -Objetivou-se com este trabalho avaliar a habilidade competitiva relativa de híbridos de canola na presença de biótipos de nabo (Raphanus sativus) e de azevém (Lolium multiflorum), em diferentes proporções de plantas na associação. Os experimentos foram instalados em casa de
-Among the weeds that cause interference with the growth and development of barley the turnip stands out, especially by the high competitive ability for the resources available in the environment. The research objective with the study was to evaluate the competitive ability of barley cultivars to live with a turnip biotype. Experiments were installed in a greenhouse, in the experimental outlining of randomized blocks designed with four repetitions. The treatments were arranged in replacement series, consisting of proportions of barley plants and turnip: 100: 0, 75:25, 50:50, 25:75 and 0: 100% which was equivalent to 20: 0, 15: 5, 10:10, 5:15 and 0:20 plants per pot. The barley was represented by BRS Cauê, BRS Elis and MN 610 and the competitor by turnip. The competitive analysis was made through diagrams applied in replacement experiments, among with use of relative competitiveness indices. The leaf area (AF) and the dry mass of the aerial part (MS) were evaluated at 50 days after the emergence of the species. The results show that there was competition between barley varieties with the turnip with mutual damage to the species involved in the community. Turnip negatively modified the AF and the MS of BRS Cauê, MN 610 and BRS Elis demonstrating higher competitive ability for the means of the resources. The interspecific competition causes greater damage to the AF and the MS species than the intraspecific competition. Thus, the turnip control is recommended the turnip control even when present at low densities of plants infesting the barley. Keywords:Hordeum vulgare, Raphanus sativus, competitive interaction. : 100:0, 75:25, 50:50, 25:75 e 0:100%, o que equivaleu a 20:0, 15:5, 10:10, 5:15 RESUMO -Entre as plantas daninhas que ocasionam interferência no crescimento e no desenvolvimento da cevada, destaca-se o nabo, em especial por apresentar elevada habilidade competitiva pelos recursos disponíveis no meio. Diante disso, objetivou-se com este trabalho avaliar a habilidade competitiva de cultivares de cevada ao conviverem com um biótipo de nabo. Foram instalados experimentos em casa de vegetação, no delineamento experimental de blocos casualizados com quatro repetições. Os tratamentos foram arranjados em série de substituição, constituídos por proporções de plantas de cevada e do nabo
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