Biomass flow in massai grass fertilized with nitrogen under intermittent stocking grazing with sheep

Marcos Neves Lopes,Roberto Cláudio Fernandes Franco Pompeu,Rodrigo Gregório Da Silva,Thaíse Cristine Ferreira De Carvalho,Luiz Barreto De Morais Neto,Magno José Duarte Cândido,Weberte Alan Sombra,Márcio José Alves Peixoto

doi:10.1590/s1516-35982013000100003

Abstract

This study evaluated the biomass flow of massai grass in regrowth subjected to different nitrogen levels (control - no fertilization; 400; 800; and 1200 N kg ha-1year-1) and under rotational stocking with sheep, in a completely randomized design with repeated measures over time. The leaf elongation rate increased with increasing nitrogen levels (N) and the fourth grazing cycle presented a lower value compared with the others. The stem elongation rate responded linearly with increasing levels of N, but it was not influenced by grazing cycles. The senescence rate of leaves remaining before grazing and after grazing were not influenced by the nitrogen fertilization or amended with successive grazing cycles. The phyllochron was influenced only by the nitrogen fertilization, with a decreasing linear response with nitrogen levels. Quadratic response was observed for the average length of leaves with increasing N levels and the grazing cycle 4 presented the lowest value for this variable. For each kilogram N ha-1 year-1, increases of 0.161 and 0.1604 kg ha-1 day-1 were verified in the herbage growth and accumulation rates, respectively. Nitrogen fertilization favors the biomass flow of massai grass, promoting an expressive increase in the production and accumulation of forage.

Highlights

The maximization of biomass production of forages is a result of satisfactory conditions of the environment and of management, which are relevant for a successful production system
This study evaluated the biomass flow of massai grass in regrowth subjected to different nitrogen levels and under rotational stocking with sheep, in a completely randomized design with repeated measures over time
The similarity in the values of this variable is explained by the method used for the management, using a variable rest period according to the nitrogen level, from the phyllochron determined by Lopes (2010), in a study with this grass subjected to nitrogen levels in a greenhouse

Summary

Introduction

The maximization of biomass production of forages is a result of satisfactory conditions of the environment and of management, which are relevant for a successful production system. The increasing restrictions to the clearing of new areas for livestock generates the demand for forages with high biomass production in response to production factors, especially soil fertility, which is the most manipulatable by man. Within this production factor, nitrogen takes on a key role by promoting positive responses to the biomass flow (Garcez Neto et al, 2002; Alexandrino et al, 2004), production and nutritional value of the forage (Andrade et al, 2003), constituting an essential management practice for the persistence and productivity of forage plants

Objectives

Methods

Results