Ecofisiologia da produção de forragem e de sementes de azevém anual sob desfolha

Abstract

The aim of the study was to evaluate the impact of defoliation frequency on the structural characteristics of plants for both forage production and seed production. The yield responses of different cultivars of annual ryegrass (Lolium multiflorum Lam.), BRS Ponteio and BRS Estações, were related to environmental variables, especially the thermal sum, to verify the morphophysiological dynamics of the plants. The present study was conducted in the field, in southern Brazil, at Embrapa Clima Temperado (ETB). Structural characteristics (number of tillers and leaves, average length of the live fraction of the leaf, heights of the last blade and ligule and leaf layer) were evaluated using the marked tiller technique; forage yield, structural components (blade, sheath plus stem and dead material), nutritive value of the harvested forage (crude protein and fiber insoluble in neutral detergent), yield and physiological quality of the seed (germination, purity, weight of a thousand seeds, emergence field, accelerated aging, root and shoot weight and length). Defoliation during the vegetative period provided forage harvesting of high nutritional value and did not affect the structure of the plant for seed production. The seeds produced showed greater weight. Defoliation soon after intense internode elongation (mid-September) determined very different structures after defoliation, however, yield and seed quality remained high. The main change in the plant, verified at the time of seed harvest, was the increase in the number of basic tillers. However, these tillers presented smaller structural variables (number of leaves, average length of the live fraction of the leaf, heights of the last blade and ligule and leaf layer). Subsequent defoliation determines drastic reductions in plant structure and, above all, in seed yield. In general, the two cultivars studied showed seeds with high physiological quality, even when subjected to high frequency of defoliation, which occurred even after the flowering of the plants.