PRODUÇÃO E QUALIDADE DE SEMENTES DE FEIJÃO-CAUPI APÓS A DESSECAÇÃO E ARMAZENAMENTO

Abstract

With the increase in cowpea (Vigna unguiculata (L.) Walp.) cultivation, it will be necessary to use herbicides for desiccation, although there are several cultivars with uneven maturity. Thus, the adoption of herbicides to ensure plants uniformity can compromise the physical and chemical quality of seeds after harvest and after storage. The objective of this study was to evaluate the effects of the desiccant herbicides use in cowpea pre-harvest and on the physical and chemical quality of seeds after harvest and after six months of storage. Three experiments were carried out, the first trial in split plot scheme (6x2), the first factor consisting of five herbicides application: 60 g ha-1 of flumioxazin, 2.5 L ha-1 of ammonium glufosinate, 2 L ha-1 paraquat, 100 g ha-1 saflufenacil, 60 mL ha-1 carfentrazone and the untreated control. And the second factor for the seed quality evaluation times: after harvest and 6 months after harvest (6 MA). And the other two trials were arranged equally in subdivided plots (5x2), the second trial consisted of the saflufenacil doses (0, 25, 50, 100 and 150 g ha-1), and the third trial consisted of the herbicide flumioxazine doses (0, 10, 20, 30 and 40 g ha-1), as primary factors, the secondary factor in both trials being the times of assessment. Both with the same evaluation periods. To verify the effects caused by the desiccation of the herbicides, the production components of the crop were evaluated, as well as the physiological quality of the seeds, through germination and vigor tests, such as the first germination count, electrical conductivity, emergence percentage, the emergency speed index, just after harvest and after the storage period. The desiccation of cowpea plants in stage R5, harmed seed damage. With desiccation, it was possible to anticipate the cowpea harvest, using paraquat, doses of 150 g i.a ha-1 of saflufenacil and 40 g i.a ha-1 of flumioxazin. The paraquat allows to anticipate the harvest in ten days, compared to the untreated area, however, this herbicide promoted lower yield, weight of a thousand seeds and normal seedlings of accelerated aging. Whereas seeds treated with paraquat were those with the highest water absorption rate. Seed yield, thousand seed weight, seed classification were not influenced by flumioxazin doses and their use allowed to anticipate the harvest by three days. For each gram of saflufenacil, a reduction of 2.05 kg ha-1 was observed in the cowpea RS, representing 52.15% of losses in the highest dose, in relation to the plots not treated with the herbicide. The cowpea seeds quality is reduced with the use of desiccant herbicides both before and after storage. Ammonium glufosinate compromises the vigor of seedlings, flumioxazin and carfentrazone affect the hue of cowpea seeds.