Densidades de semeadura de cultivares de azevém diploide ou tetraploide

Abstract

Among the ryegrass genotypes that are classified through their ploidy, it can be highlighted that there are two groups, diploid and tetraploid ryegrass. Seed densities proposed for these cultivars are around 20 to 25 kg ha-¹ of pure and viable seeds, values that for the agronomic characteristics of the cultivars can be variable. In order to indicate the most adequate density for each ploidy level, 5 densities and two ryegrass cultivars were tested. The experiment occurred at the coordinates 29°09'33.9"S 56°33'15.2" W, with climate classified as cfa, and the soil being a Plinth soil argiluvic dystrophic. The experimental design was of randomized blocks in plots of 5 lines by 5 m in length, with 4 blocks, and the treatments were 5 sowing densities that are: D1 – 5 kg ha-¹; D2 – 12,5 kg ha-¹; D3 – 25 kg ha-¹; D4 – 37,5 kg ha-¹; D5 – 50 kg ha-¹, and the cultivars, a diploid: BRS Ponteio, and a tetraploid: Potro®. The dry matter yield (kg DM ha-¹), the dry matter accumulation rate (kg ha-¹ day-¹) and the morphological composition (% DM) were evaluated. The data were submitted to analysis of variance and after the Tukey test the probability of 5%. There was no effect of the interaction between cultivars and densities, so the quadratic model and the segregated regression for ryegrass densities independent of the cultivar were adjusted. By the segmented regression it was observed that densities above 15.37 kg ha-¹ do not differ for DM production. For the accumulation rate it was observed that there was interaction (P <0.001) between cultivars and densities in the first cut, where there was density effect only to cultivar BRS Ponteio and that the best (P <0.001) density was 25 kg ha-¹, leads to an earlier grazing. It was verified that the density of 15 kg ha-¹ should be used when total dry matter production is objectified. In order to anticipate the use of forage, the cultivar BRS Ponteio with 25kg ha-¹ should be used. For the best forage quality, the cultivar Potro® should be used.