Efeito do espaçamento entre linhas e de corte na produção de sementes de Brachiaria brizantha cvs. Marandu e Xaraés

Abstract

This experiment was conducted at EMBRAPA Beef Cattle, in Campo Grande, MS, from November/2004 to August/2005 and its objective was to evaluate the dynamics of Brachiaria brizantha cvs. Marandu and Xaraés seeds production submitted to different spacings and with or without defoliation. The experimental design used was a complete randomized blocks in a split-split-plot arrangement and the t test was used for averages comparison (p < 0,05). The treatments were conducted in two cultivars of B. brizantha, Marandu and Xaraés, that were allocated to the portions, defoliation (with or without defoliation) allocated in the subpportions and three spacings among lines (0,4; 0,8 and 1,2 m) allocated in the subsubportions. In this arrangement, three repetitions were done. It was evaluated the average number of tillers/m2 in two different physiologic stadiums; the average number of inflorescences/m2 in two different moments of reproductive period; the total number of inflorescences/m2, the racims/inflorescences number; the percentage of reproductive tillers, the total amount of dry mass acumulation by hectare; the amount of pure seeds produced by hectare; the percentage of physical purity of the seeds; the percentage of no-fertile florets (straw) and the weight from 1000 seeds. The seeds production of the evallueted cultivars answered in a similar way to the evaluated factors (cutting plants and spacing among lines), being recommended for both the seedling in the spacing of 1,2 m and the cutting plants at 10 cm of height to 54 DAE. The cultivars differed among themselves at seeds production, tillers production, inflorescences, percentage of reproductive tillers, percentage of physical purity, percentage of no-fertile florets and in the weight of 1000 seeds. The cutting plants influenced positively the number of tillers and of inflorescences/m2 and the percentage of physical purity of the seeds. However, the cut did not influence the production of pure seeds directly, although it has promoted increments in the tillers production and inflorescences from both cultivars.