Ecofisiologia de produção forragem de azevém cv. BRS Integração sob diferentes intensidades de desfolhas em diferentes momentos fenológicos

Abstract

The objective of this study was to evaluate the morphophysiological responses of an early cultivar (BRS Integração) of annual ryegrass (Lolium multiflorum Lam.) subjected to different defoliation intensities at different phenological moments of the crop. The experiment was conducted at the Terras Baixas Experimental Station of Embrapa Clima Temperado (31°80’S and 52°40’W), in the municipality of Capão do Leão/RS. The defoliation intensities were 0% (close to the ground), 25% and 50% of the plant height at the pre-defoliation moment, which were managed with a single defoliation frequency, the time required for the expansion of two leaves (2F). The 4 phenological moments resulted from the 1st; 2nd; 3rd and 4th regrowth. The experimental design was randomized blocks in a 3x4 factorial scheme (3 intensities x 4 moments) with 3 replications. The data were subjected to analysis of variance and the means were compared by Tukey's test (p<0.05). At the time of the first regrowth, there was adequate structure and high harvest of live blades in the less intense defoliation (50% of the plant height). The more intense defoliation (close to the ground) provided a higher forage harvest only at the time of the first cut, but the crude protein and structure were worse. In the second regrowth, there were no differences in the amount of forage harvested. The high proportion of live blades harvested in the less intense defoliation remained, but the structure and nutritional value were better in the intermediate defoliation. In the third and fourth regrowths, the best structure and nutritional value occurred in more intense defoliations (0% and 25%); especially due to the greater control of internode elongation. However, among the most intense, intermediate defoliation allowed for a greater forage harvest, since there was less death of fewer tillers in relation to the most intense defoliation (close to the ground). Intermediate defoliation also presented a greater forage harvest in comparison to the least intense defoliation (50%). Thus, the intermediate defoliation intensity determines the best morphophysiological responses, from the forage aspect, of the early cycle annual ryegrass, since it concomitantly provides a high quantity of harvested forage with high protein value at the different defoliation moments.