Recebido para publicação em 16.7.2015 ABSTRACT -Weeds have the potential to dramatically interfere in cassava cultivation, reducing its productive potential; however, there are few studies on the selective herbicides in this crop. Therefore, the objective was to evaluate in this work the selectivity and efficiency of sulfentrazone in cassava crops grown in sandy and clayey soils. Two experiments were carried out: The first one was carried out in sandy soil conditions in the conventional system; and the second one was carried out in clayey soil conditions in the no-tillage system. The experimental design was a randomized block with four replications. The treatments consisted in doses of 250, 500, 750 and 1,000 g ha -1 of sulfentrazone, and weeded and non-weeded controls. Sulfentrazone application in cassava crops has linearly reduced the production of roots in a proportion of 0.0153 and 0.0107 t ha -1 at each increment in grams of the active ingredient, respectively. It was concluded that sulfentrazone was not selective for cassava crops grown both in sandy and in clayey soil; however, it was highly effective in weed control in both soils.
Competition with weeds is one of the obstacles to achieve high yields in jatropha harvest. The chemical method is an alternative weed control due to its high efficiency, readiness and economy, when compared to other methods. However, products recommended for this crop are scarce. This study aimed at evaluating the effects of pre and post-emergence clomazone formulations at the initial development of jatropha. Two experiments were conducted under a randomized blocks design, in a 2 x 5 factorial arrangement, with four replications, consisting of the combination of two clomazone formulations (encapsulated suspension and emulsifiable concentrate) and five doses (0 g ha-1, 250 g ha-1, 500 g ha-1, 1,000 g ha-1 and 2,000 g ha-1). The dry matter of the plants was reduced both in the pre-emergence and post-emergence applications. Net photosynthesis was not affected by the application of clomazone in both formulations. The encapsulated suspension formulation is less phytotoxic than the emulsifiable concentrate formulation for pre and post-emergence applications. However, both formulations negatively affect the early development of jatropha plants.
This experiment aimed to study the effects on grain and forage productivity in dual-purpose wheat cv. BRS Tarumã under cutting handlings and nitrogen fertilization. The experiment was conducted in area of Rhodic Hapludox in the city of Marechal Cândido Rondon, Paraná State, in a randomized block design with 12 treatments and four replications. The treatments consisted of surface nitrogen levels (0, 60, 120 and 180 kg ha -1 ) and number of cuttings accomplished (0, 1 and 2). The topdressing was split in two applications for handling of just a cutting (27 and 65 days after sowing -DAS), and three applications for handling with two cuttings (27, 65 and 96 days after sowing -DAS). Data were subjected to analysis of variance (p≤0.05). The use of one or two cuttings and the comparison between the first and second cuttings were done by F test (5%) whereas nitrogen doses were studied by regression analysis. For all variables, there was significant interaction of nitrogen doses in surface and the number of cuttings. Grain yield and its yield components were responsive to levels of nitrogen fertilization in surface as well as forage production and its quality, but the same factors were reduced with the use of cuttings. This handling increased the dry matter content and crude protein in grains.
Resumo Objetivou-se avaliar o perfil metabólico de 24 ovinos Santa Inês, machos, com peso vivo médio inicial de 20±1,25 kg, submetidos à restrição alimentar seguida de realimentação em confinamento, distribuídos em quatro tratamentos com 0, 20, 40 ou 60% de restrição alimentar. Dois ensaios foram desenvolvidos, um referente à restrição e outro à realimentação. Para tanto, foi utilizado delineamento experimental inteiramente ao acaso, com quatro tratamentos e seis repetições. Observou-se na fase de restrição alimentar que houve um decréscimo linear para as concentrações bioquímicas de ureia, glicose, GGT e fósforo; contrariamente, a concentração de colesterol aumentou linearmente ao final do período restritivo. A restrição alimentar influenciou negativamente nas concentrações de triglicerídeos e creatinina, diferentemente, os valores de proteínas totais e albumina apresentaram aumento significativo com o período restritivo. Já na realimentação, observou-se comportamento linear decrescente para ureia, glicose, GGT e magnésio. No segundo ensaio, verificou-se que as concentrações de proteínas totais, globulina e creatinina apresentaram diferença (P<0,05) entre os períodos de coleta. Os níveis de restrição alimentar afetaram o metabolismo proteico e interferiram também no metabolismo energético e mineral e a realimentação resultou em alteração no metabolismo proteico e energético.
The objective of this work was to evaluate the effect of weed competition on the accumulation of nitrogen and phosphorus in the leaves and on the dry weight of the roots of cassava (Manihot esculenta) in the conventional and no-tillage systems, in two crop cycles. The experiments were carried out in a randomized complete block design, with split-split plots and four replicates. The plots consisted of conventional tillage or no-tillage; the split plots, of the competition or not with weeds; and the split-split plots, of the evaluation periods (0, 25, 50, 75, 100, 125, 150, 175, 200, and 225 days after planting/pruning). In the first cycle, weed competition reduced the accumulation of nitrogen in 82.6 and 81.3% and of phosphorus in 65.7 and 85.3% under conventional tillage and no-tillage, respectively. In the second cycle, the reductions in the accumulation of nitrogen were of 41.1 and 52.4% and of phosphorus of 44.1 and 52.6%, in conventional tillage and no-tillage, respectively. The root dry weight of cassava grown with weed competition showed reductions of 15.8 and 11.2% under conventional tillage and no-tillage, respectively, only in the second cycle. Weed competition reduces the accumulation of nitrogen and phosphorus in the leaves of cassava in the conventional and no-tillage systems in both crop cycles, but reduces the dry matter of cassava roots only in the second cycle.
-This study has aimed to evaluate selectivity and efficiency in weed control of flumioxazin and S-metolachlor in 'Baianinha' cassava crops. The experimental design was randomized blocks with four replications. Treatments consisted in doses of flumioxazin of 50, 75, 100 and 125 g ha -1 a.i. and doses of S-metolachlor of 960, 1920, 2880 and 3840 g ha -1 a.i., besides weeded and unweeded controls. Treatments application was carried on 10/11/2013, 13 days after planting (DAP) and cassava cuttings presented underground sprouts measuring 3.0 to 4.5 cm. Flumioxazin at the highest dose provided 61.5% reduction of weeds biomass while S-metolachlor at the highest dose reduced 63.7% in the weeds biomass. Both herbicides have not promoted phytointoxication and have not altered roots yield and starch content of cassava plants. In conclusion, the herbicides were selective for 'Baianinha' cassava and efficient in weed control. However, control level increased with increments of doses assessed. Keywords: herbicides; Manihot esculenta; weeds; selectivity Resumo -Objetivou-se avaliar a seletividade e a eficiência no controle de plantas daninhas do flumioxazin e do S-metolachlor na cultura da mandioca 'Baianinha'. O delineamento experimental utilizado foi de blocos casualizados com quatro repetições. Os tratamentos consistiram nas seguintes doses do flumioxazin 50, 75, 100 e 125 g ha -1 i.a. e as doses do S-metolachlor foram 960, 1920, 2880 e 3840 g ha -1 i.a., além de uma testemunha sem capina e outra capinada. A aplicação dos tratamentos foi realizada em 11/10/2013, 13 dias após o plantio (DAP) e a maniva apresentava brotos subterrâneos com 3,0 a 4,5 cm. O flumioxazin na maior dose proporcionou 61,5% de redução da biomassa das plantas daninhas, enquanto que o S-metolachlor na maior dose reduziu 63,7% na biomassa de plantas daninhas. Ambos os herbicidas não promoveram fitointoxicação e não alteraram a produtividade de raízes e teor de amido das plantas de mandioca. Concluiu-se que, os herbicidas foram seletivos para a mandioca 'Baianinha' e eficientes no controle das plantas daninhas. Entretanto, o nível de controle aumentou de acordo com incrementos das doses avaliadas.
The study aimed to determine the interference periods of weeds in cassava ‘IAC 90’ cultivated in different cycles and cropping systems. An experiment was conducted in the period 2014/15 (1st cycle) and another was conducted from the pruning of cassava plants in the period 2015/16 (2nd cycle). The experimental design was a randomized block design with split-split plots and four replicates. The plots represented the cropping systems (conventional and no-tillage) and the split-split plots corresponded to the periods with and without coexistence with weeds (0, 25, 50, 75, 100, 125, 150, 175, 200 and 225 days after planting or pruning - DAP/DAPr). In the 1st cycle, there was no interaction between the cropping systems and the coexistence periods and, therefore, based on the acceptable losses of 5% in the root and starch yield of 'IAC 90' cassava, the PCPI was estimated between 20 and 212 DAP and 14 to 214 DAP, respectively. In the 2nd cycle, the CPPWI ranged from 17 to 176 DAPr and 30 to 216 DAPr based on the root and starch yield obtained in the conventional method, respectively. While in no-tillage, the estimated CPPWI ranged from 18 to 198 DAPr and 9 to 218 DAPr based on root and starch yield, respectively. In general, the data indicate that conventional weed management should be carried out in a more intensified way than in no-tillage. In addition, CPPWI based on starch losses can avoid losses in root production.
-Weeds interfere dramatically in the productive potential of cassava; however, information regarding herbicides that are selective to crops is still scarce. Thus, the aim in this study was to assess the initial growth of IAC 90 cassava plants after the application of sulfentrazone at different stages of germination of cassava in clayey and sandy soils. Three experiments were simultaneously deployed: the first experiment consisted in the application of sulfentrazone in the non-germinated stage of cassava cuttings; the second one in the stage of germinated cassavas cuttings (0.9 cm shoots); and the third one in applications in the stage of cassava cuttings with buds emerging (6.5 cm shoots and emerging from the soil). For each experiment the experimental design in randomized blocks was used in the 2 x 5 factorial arrangement with four replications. The factors were composed of two soils (sandy and clayey) and five doses of sulfentrazone (0, 250, 500, 750 and 1,000 g ha -1). It was found that depending on the herbicide dose, development stage of the buds of cassava cuttings and the type of soil, damage can occur in the initial development of the IAC 90 cassava plants. The greatest potential of sulfentrazone selectivity has occurred in applications in the nongerminated cassava cuttings stage and in doses lower than 500 g ha -1in the clayey soil.Keywords: herbicide, Manihot esculenta, protox inhibitor, selectivity. RESUMO -As plantas daninhas interferem drasticamente no potencial produtivo da mandioca
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