Produção de forragem e qualidade nutricional de cultivares diploides e tetraploides de azevém anual

Abstract

Annual ryegrass is the cool-season grass forage specie most used in southern Brazil. In recent years, many improved materials developed in other regions of the world, were inserted in the Brazilian market, including, diploid and tetraploid cultivars. The hypothesis of this research is that tetraploid materials, beyond be more productive, present a longer production cycle, allowing a longer use of pasture. The objectives of this research was evaluate the performance of materials under grazing, detecting differences in nutritional quality among cultivars, as well as the difference between diploid and tetraploid, and also the production of total forage. The experiment was conducted under field conditions on experimental design a randomized block design with four replications. It was evaluated twelve genotypes of Annual ryegrass, six diploid (INIA Bakarat, INIA Camaro, La Estanzuela 284, BRS Estações, BRS Ponteio, Nibbio) and six tetraploid (INIA Titan, INIA Scorpio, Winter Star, KLM 138, Barjumbo, Potro). The seeding rate was 20 and 25 kg ha-1 of pure and viable seeds for diploid and tetraploid, respectively. The P and K fertilization was according to the soil analysis. Nitrogen fertilization on cover was 150 kg ha-1. The beginning of the grazing occurred when sward canopy height reached 25 cm, and the stubble was kept at 10 cm. Criolo horses breed (450 kg) were used in mob grazing method to keep the target canopy heights. The variables studied were forage production, crude protein, neutral detergent fiber (NDF) and acid detergent fiber (ADF). In this research was expected to identify diploid materials and / or tetraploid, most promising for the different systems production, managements and forage planning to use in Southwest Paraná. It was significant differences (P<0.05), which tetrapoloid cultivars performed better, presenting longer cycle than diploid ones. In relation to the nutritional quality, NDF contents were statistical different among both grazing and cultivars. In relation to FDA content there were differences among all grazings, whereas among cultivars were differences just in the first and last grazing. The crude protein did not differ significantly (P>0.05) among cultivars, with differences only among grazing, reducing the crude protein with the results from the productive ryegrass cycle.