Cultivares tetraplóides de azevém (Lolium multiflorum) submetidos a níveis de adubação

Abstract

The cultivation of ryegrass (Lolium multiflorum) is a viable alternative for the southern region, since it has a productive potential in the fall winter periods. However, some management practices, such as height, frequency of cuts and nutrient doses, are of great importance in the determination of crop yield, with fertilization being a determinant factor to maintain the productivity of livestock in grazing systems. The objective of this work was to evaluate the dry matter production as well as the bromatological composition of three tetraploid ryegrass cultivars submitted to fertilization levels. Two experiments were carried out at the Atlântica Sementes S.A. experimental station in Piraí do Sul, PR, located at the geographic coordinates 24° 36' 45" S and 50° 00' 27" W, at 1078m altitude. The soil of the experimental areas is classified as Red Yellow Latosol, clayey. The cultivars of Azevém (Lolium multiflorum) tetraploid were Bar HQ, Barjumbo and Potro. The treatments for experiment 1 corresponded to three levels of nitrogen fertilization in coverage, being: 0N = 0 kg ha¯¹ of N, 60N = 60 kg ha¯¹ of N, 100N = 100 kg ha¯¹ of N and the treatments for experiment 2 corresponded to two levels of NPK base fertilization (8:20:15), being 0NPK = 0 kg ha¯¹ NPK and 300NPK = 300 kg ha¯¹ NPK. The experimental design was a randomized block with four replications, with each plot presenting an area of 4.25 m². To determine the total dry matter yield, samples were taken of the two successive cuts made in the plots and taken to a forced air circulation oven at 60ºC for 72 hours. For the determination of the bromatological composition the samples passed through the milling process and were sent to the laboratory. The laboratory analyzes were performed at the Laboratory of Bromatology and Animal Nutrition, at the Federal University of Pampa - UNIPAMPA, Campus Itaqui - RS, in which it determined the percentage MS%, MM%, PB%, FDN% and FDA%. The data were submitted to analysis of variance, and the means of the variables were compared by the Tukey test at 5% of the probability of error. For both experiments, the cultivar Barjumbo presented higher total dry matter yield, reaching 15.59 t.ha¯¹ MST in experiment 1 and 16.45 t.ha¯¹ in experiment 2 if it proved to be more productive under conditions and between the cultivars tested. Regarding the nutritional quality of the ryegrass pasture, the cultivar Bar HQ was superior to the other cultivars under the conditions tested, presenting the highest crude protein content and the lowest fiber content.