Produção e valor nutritivo de pastagens de tifton 85 sobressemeadas com azevém e inoculadas com Azospirillum brasilense

Abstract

The inoculation of plants with Azospirillum brasilense associated with chemical sources of nitrogen fertilizer can increase the efficiency of nitrogen use and reduce the amount used. In forage systems whose base is bermudagrass (Cynodon dactylon (L.) Pers.), studies on the effects of A. brasilense are scarce. In this sense, it was evaluated the production, nutritive value of forages and the response of the animals in pastures based on Tifton 85 bermudagrass in association with ryegrass (Lolium multiflorum Lam.), “BRS Ponteio” and inoculated with A. brasilense and fertilized with doses of nitrogen fertilizer, grazed by lactating cows. Three forage systems were evaluated: (i) Tifton 85 + A. brasilense + 180 kg N ha-1 year-1; (ii) Tifton 85 + 230 kg N ha-1 year-1 and (iii) Tifton 85 + 280 kg N ha-1 year-1. The experimental design was completely randomized, with three treatments (forage systems), three repetitions (paddocks) and repeated measures over time (grazing cycles). Forage samples were collected before and after grazing to evaluate the responses of plants and animals. The inoculation of A. brasilense in pasture, based on Tifton 85 bermudagrass, mixed with ryegrass, (plus 180 kg of N ha-1), shows a positive effect when compared to the pasture fertilized with 230 kg of N ha- 1, in the response of plants and animals. The inoculation with A. brasilense resulted in savings of 70 kg N ha- 1 year-1 (40 kg N ha-1 in winter and 30 kg N ha-1 in summer). The nutritional value and the responses of the animals did not differ between the forage systems. A better result in forage production was obtained in the pasture with a higher dose of nitrogen fertilizer.