Banco de sementes e manejo de azevém em culturas agrícolas

Abstract

In Rio Grande do Sul (Brazil), the annual ryegrass is a fodder plant used for animal feed, and it is also considered an important weed in crops during the cold period of the year. Three works were conducted, the first work (I) was conducted in two years, it was evaluated the effects of these soil cropping systems and of crop rotation in the reduction of the population and the anual ryegrass seed bank. In the second work (II) the objective was to evaluate the suppressor potential of winter crops on the annual ryegrass and also their contribution in reducing the seed bank. The experiment was conducted in two agricultural years, the used winter crops were wheat, black oat, rye, barley, canola, vetch, wild turnip and the fallow is with ryegrass (control) and in the subplots, treatments with and without control (chemical or mechanical) of annual ryegrass. The third work (III) was conducted in order to evaluate the potential of herbicides in the quality reduction of ryegrass seeds in wheat. The methyl iodosulfurom herbicides were applied (5 g of active ingredient (a.i.) ha-1 in wheat tillering; glufosinate (350 g ai ha-1 in pre-harvest physiological maturity) of wheat; combination of these two herbicides and control treatment (control); and evaluated the weight of a thousand seeds, germination and vigor of ryegrass and wheat. The results demonstrated that the systems with rotation of winter and summer crops reduce the population of ryegrass, regardless the tillage system being direct or conventional. The crop rotation is effective in reducing ryegrass seed bank, regardless the cultivation system being direct or conventional highlighting the crop rotation systems that include maize in the summer (I). The use of winter crops is an important tool in the management of annual ryegrass, with the reduction in the plant height, dry matter and lower replenishment of soil seed bank; and among winter crops stand out radish, rye and vetch (II). In ryegrass the two treatments with application of glufosinate ammonium in pre-harvest grain, reduce the weight of a thousand seeds, germination and seedling vigor. In wheat, the use of glufosinate ammonium in pre-harvest, associated with methyl iodosulfurom applied at the beginning of tillering, reduces the seed vigor, however, without affecting germination (III).