Manejo de herbicidas no consórcio milho-braquiária e eficácia de controle de plantas daninhas em diferentes regimes de chuva
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Data
2020-10-30
Autores
Ribeiro, Nagilla Moraes
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Universidade Estadual Paulista (Unesp)
Resumo
O consórcio de milho-braquiária tem se consolidado ao longo dos anos como uma técnica viável e produtiva, permite elevada produção de resíduos e tem potencial para reduzir a infestação de plantas daninhas. A aplicação de subdoses de herbicidas seletivos à cultura do milho é uma alternativa para a supressão do crescimento inicial da forrageira, evitando prejuízos tanto no rendimento como na qualidade de grãos. A presença de palha pode influenciar no manejo dos herbicidas pré-emergentes, pode afetar sua transposição para o solo, impactando, por consequência, na eficácia de controle das plantas daninhas. Os estudos sobre manejo e eficácia de herbicidas aplicados sobre palha ainda são escassos, e, em grande parte, têm sido feitos sobre palha de cana-de-açúcar. Diante disso, o objetivo deste estudo foi avaliar os efeitos de subdoses de herbicidas pós‑emergentes no consórcio de milho e braquiária, bem como avaliar a eficácia de diclosulam, flumioxazin e diuron+sulfentrazone na palhada de milho+braquiária e no solo, em diferentes regimes de chuva. Para tal, foram realizados dois experimentos. O primeiro experimento avaliou os efeitos de subdoses de herbicidas pós‑emergentes no consórcio de milho e braquiária. Este estudo foi conduzido em delineamento de blocos ao acaso, com esquema fatorial 3 x 8, sendo três sistemas de cultivos: milho solteiro, consórcio 1 (milho + Urochloa ruziziensis) e consórcio 2 (milho + U. decumbens), e oito tratamentos: atrazine (1500 g i.a. ha-1); atrazine + mesotrione (1500+ 60 g i.a. ha-1); atrazine + mesotrione (1500+ 40 g i.a. ha-1); atrazine + glyphosate (1500 g i.a. ha-1 + 45 g e.a. ha-1); atrazine + glyphosate (1500 g i.a. ha-1+ 22,5 g e.a. ha-1); atrazine + nicosulfuron (1500+ 7 g i.a. ha-1); além de dois tratamentos testemunhas (capinada e não capinada). Os herbicidas foram aplicados no estádio fenológico V6 para o milho, U. ruziziensis no estádio de 5-7 perfilhos e U. decumbens no estádio de 4-6 perfilhos. O segundo experimento avaliou a eficácia de diclosulam, flumioxazin e diuron+sulfentrazone na palhada de milho+braquiária e solo, em diferentes regimes de chuva, na eficácia de controle de Ipomoea hederifolia. O delineamento experimental utilizado foi o inteiramente casualizado, adotado de forma isolada para cada um dos herbicidas diclosulam (35,03 g i.a. ha-1), flumioxazin (25 g i.a. ha-1) e diuron+sulfentrazone (diuron: 455 g i.a. ha-1+ sulfentrazone: 255,5 g i.a. ha-1). Foram avaliados cinco períodos sem chuva após a aplicação dos herbicidas (0, 2, 5, 7 e 10 dias após a aplicação), duas coberturas (com e sem palha do consórcio milho + braquiária) e quatro lâminas de chuvas (0, 10, 20 e 30 mm). Para o primeiro experimento o nicosulfuron proporcionou o menor acúmulo de biomassa seca para as espécies. As subdoses dos herbicidas afetaram o rendimento da palhada. No entanto, a produção de palha do consórcio superou a do cultivo solteiro. Para o segundo experimento o diuron+sulfentrazone apresentou melhor controle na presença de palha do consórcio de milho e braquiária, em relação aos herbicidas diclosulam e flumioxazin. O diuron+sulfentrazone foi eficaz no controle de I. hederifolia, e o diclosulam e flumioxazin não foram eficazes. Conclui-se que o maior incremento de palhada ocorreu no consórcio de milho com U. ruziziensis, e que os diferentes regimes de chuva e a presença de palha afetaram a eficácia do diclosulam e flumioxazin.
The intercropping of corn-brachiaria has consolidated itself over the years as a viable and productive technique, allowing high waste production and has the potential to reduce weed infestation. The application of underdoses of selective herbicides to the corn crop is an alternative to suppress the initial growth of forage, avoiding losses in both yield and grain quality. The presence of induced straw can in the management of pre-emergent herbicides, can affect its transposition to the soil, consequently impacting on the effectiveness of weed control. Studies on the management and effectiveness of herbicides on straw are still scarce, and, to a large extent, they have been carried out on sugarcane straw. Given this, the objective of this study was to evaluate the effects of post-emergent herbicide underdoses in the corn and brachiaria intercropping, as well as to evaluate the effectiveness of diclosulam, flumioxazin and diuron + sulfentrazone in the corn straw + brachiaria and in the soil, in different rain regimes. For this, two experiments were carried out. The first experiment evaluated the effects of post - emergent herbicide underdoses in the corn and brachiaria intercropping. This study was conducted in a randomized block design, with a 3 x 8 factorial scheme, with three cultivation systems: single corn, intercropping 1 (corn + Urochloa ruziziensis) and intercropping 2 (corn + U. decumbens), and eight treatments: atrazine (1500 g a.i. ha-1); atrazine + mesotrione (1500+ 60 g a.i. ha-1); atrazine + mesotrione (1500+ 40 g a.i. ha-1); atrazine + glyphosate (1500 g a.i. ha-1 + 45 g a.i. ha-1); atrazine + glyphosate (1500 g a.i. ha-1 + 22.5 g a.i. ha-1); atrazine + nicosulfuron (1500+ 7 g a.i. ha-1); besides two witnesses (weed and not weed). The herbicides were applied at the phenological stage V6 for corn, U. ruziziensis at the stage of 5-7 tillers and U. decumbens at the stage of 4-6 tillers. The second experiment evaluated the efficacy of diclosulam, flumioxazin and diuron + sulfentrazone on stubble corn+brachiaria and soil, under different rain regimes, on the effectiveness of controlling Ipomoea hederifolia. The experimental design used was completely randomized, adopted in isolation for each of the herbicides diclosulam (35.03 g a.i. ha-1), flumioxazin (25 g ia ha-1) and diuron + sulfentrazone (diuron: 455 g ia ha-1+ sulfentrazone: 255.5 g ai ha-1). Five periods without rain were obtained after the application of the herbicides (0, 2, 5, 7 and 10 days after application), two coverings (with and without straw from the corn + brachiaria intercropping) and four layers of rain (0, 10, 20 and 30 mm). For the first experiment, nicosulfuron provided the lowest accumulation of dry biomass for the species. As underdoses of the herbicides affected the straw yield. However, the intercropping's straw production surpassed that of single cultivation. For the second experiment, diuron + sulfentrazone showed the best control in the presence of corn and brachiaria intercropping straw, in relation to the herbicides diclosulam and flumioxazin. Diuron + sulfentrazone was effective in controlling I. hederifolia, and diclosulam and flumioxazin were not effective. It was concluded that the largest increment of straw occurred in the intercropping of corn with U. ruziziensis, and that the different rain regimes and the presence of straw affected the effectiveness of diclosulam and flumioxazin.
The intercropping of corn-brachiaria has consolidated itself over the years as a viable and productive technique, allowing high waste production and has the potential to reduce weed infestation. The application of underdoses of selective herbicides to the corn crop is an alternative to suppress the initial growth of forage, avoiding losses in both yield and grain quality. The presence of induced straw can in the management of pre-emergent herbicides, can affect its transposition to the soil, consequently impacting on the effectiveness of weed control. Studies on the management and effectiveness of herbicides on straw are still scarce, and, to a large extent, they have been carried out on sugarcane straw. Given this, the objective of this study was to evaluate the effects of post-emergent herbicide underdoses in the corn and brachiaria intercropping, as well as to evaluate the effectiveness of diclosulam, flumioxazin and diuron + sulfentrazone in the corn straw + brachiaria and in the soil, in different rain regimes. For this, two experiments were carried out. The first experiment evaluated the effects of post - emergent herbicide underdoses in the corn and brachiaria intercropping. This study was conducted in a randomized block design, with a 3 x 8 factorial scheme, with three cultivation systems: single corn, intercropping 1 (corn + Urochloa ruziziensis) and intercropping 2 (corn + U. decumbens), and eight treatments: atrazine (1500 g a.i. ha-1); atrazine + mesotrione (1500+ 60 g a.i. ha-1); atrazine + mesotrione (1500+ 40 g a.i. ha-1); atrazine + glyphosate (1500 g a.i. ha-1 + 45 g a.i. ha-1); atrazine + glyphosate (1500 g a.i. ha-1 + 22.5 g a.i. ha-1); atrazine + nicosulfuron (1500+ 7 g a.i. ha-1); besides two witnesses (weed and not weed). The herbicides were applied at the phenological stage V6 for corn, U. ruziziensis at the stage of 5-7 tillers and U. decumbens at the stage of 4-6 tillers. The second experiment evaluated the efficacy of diclosulam, flumioxazin and diuron + sulfentrazone on stubble corn+brachiaria and soil, under different rain regimes, on the effectiveness of controlling Ipomoea hederifolia. The experimental design used was completely randomized, adopted in isolation for each of the herbicides diclosulam (35.03 g a.i. ha-1), flumioxazin (25 g ia ha-1) and diuron + sulfentrazone (diuron: 455 g ia ha-1+ sulfentrazone: 255.5 g ai ha-1). Five periods without rain were obtained after the application of the herbicides (0, 2, 5, 7 and 10 days after application), two coverings (with and without straw from the corn + brachiaria intercropping) and four layers of rain (0, 10, 20 and 30 mm). For the first experiment, nicosulfuron provided the lowest accumulation of dry biomass for the species. As underdoses of the herbicides affected the straw yield. However, the intercropping's straw production surpassed that of single cultivation. For the second experiment, diuron + sulfentrazone showed the best control in the presence of corn and brachiaria intercropping straw, in relation to the herbicides diclosulam and flumioxazin. Diuron + sulfentrazone was effective in controlling I. hederifolia, and diclosulam and flumioxazin were not effective. It was concluded that the largest increment of straw occurred in the intercropping of corn with U. ruziziensis, and that the different rain regimes and the presence of straw affected the effectiveness of diclosulam and flumioxazin.
Descrição
Palavras-chave
Cultivos consorciados, Precipitação, Supressão, Dinâmica na palha, Intercropping, Suppression, Straw, No-tillage system