Estratégias de uso de pastagens naturais: dinâmica vegetacional e desenvolvimento de novilhas de corte

Abstract

The objective of this study is to evaluate the effect of grassland intensification strategies in the productivity and structure of the pasture, grassland composition and on body development of heifers. Strategies evaluated were: Deferred natural grassland (DEFERRED): Natural grassland fertilized with Lime, phosphorus, and potassium (FERTILIZATION); Fertilized natural grassland with overseeding of ryegrass and clovers (LEGUME); Fertilized natural grassland with overseeding of ryegrass and nitrogen fertilization (NITROGEN). The evaluated animals were Braford beef heifers, keeping at the experimental area from 08/05/2015 to 12/13/2016, under continuous stocking at a forage allowance of 12%. The experimental design was a randomized block design with repeated measures over time with two replications. The forage accumulation rate and the average daily gain differed between strategies in winter and spring, with higher values for strategies with species overseeded (LEGUMES and NITROGEN). DEFERRED and FERTILIZATION supported higher stocking rates in the first winter, allowing similar gains per area among all the strategies during the evaluated period. Strategies with species introduction showed reduction (P <0.05) of forage mass of C4 perennial grass groups, decrease of Paspalum dilatatum, Paspalum umbrosum e Axonopus, and increase of undesirable group mass. The Shannon Index was not changed and species richness was lower in the NITROGEN strategy. Only heifers of the LEGUMES and NITROGEN strategies reached puberty. The intensification strategies evaluated alter the floristic composition of the natural grassland, reducing the species richness in the higher levels of N applied.