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Clearfield® technology is an important tool for chemical weed management in rice fields, however, carryover of these herbicides is still a concern for crops in succession. In this study, we aimed to evaluate the impact of the herbicide Kifix® (imazapic + imazapyr) associated with Clearfield® technology of rice crops on ryegrass in succession, as well as on non-Clearfield® rice and soybean grown in rotation, in addition to the control potential of jointvetch (Aeschynomene rudis and A. denticulata) from 2016 to 2018. The experiments comprised the application of Kifix® to Clearfield® rice grown in the first experimental year, evaluating its impact (1st summer) on ryegrass grown the following winter, as well as on soybean, rice and non-Clearfield® rice grown the following summer (2nd summer). The results reported reductions in jointvetch density and infestation as Kifix® doses increased; as well as mild damage from Kifix® residues on ryegrass sown in succession to Clearfield® rice, as well as on non-Clearfield® rice and soybean in rotation to Clearfield® rice. In addition, the possibility of residue accumulation of Kifix® in the soil after repeated applications should be verified in further studies. [ABSTRACT FROM AUTHOR]

Among the weed species infesting soybean, Alexandergrass (Urochloa plantaginea) is highlighted as one of the most competitive. The objective of this work was to determine the periods of interference of Alexandergrass, and is effects, on morphophysiology and yield components of soybean. Treatments were pooled into two groups: the group "convivence" comprised soybean growing among Alexandergrass for increasing periods: 0, 7, 14, 21, 28, 35 and 42 days after emergence (DAE), as well as along all the crop cycle. The "control" group comprised soybean free from competition for the same time lapses. Forty-two DAE, soybean morphophysiology was assessed. There was no effect of the time lpse of Alexandergrass "control" or "convivence" on soybean physiological performance. Plant height, stem diameter, plant dry mass, leaf area and grain yield components of soybean were, however, affected by Alexandergrass. The critical period of interference prevention comprises 26-41 DAE; the period prior to interference is 26 DAE; and the total period of interference prevention is 41 DAE. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]