Volume of the syrup and the concentration of fire retardants in prescribed burnings in an eucalyptus area in the Cerrado-Amazon transition

Abstract

The chemical firebreaks consist of bands with applications of fire retardants and are used in the indirect combat of forest fires. Despite its efficiency, the lack of practical use recommendations restricts the application and effectiveness of the products. This paper evaluated the efficiency of fire retardants in controlled burning in area of 6.0 years old of the Eucalyptus urograndis (Eucalyptus grandis x Eucalyptus urophylla) (clone H13) by applying different concentrations of product and volumes of the syrup, after 1.0h of retardants application. Two commercially fire retardants (Phos-Chek WD881® and Hold Fire®) and an alternative (hydro retainer polymer - Nutrigel®) were tested with five concentrations each and volumes of the syrup of 0.5; 1.0 and 2.0 L m-2 (only water and without application syrup were the references). The fire behavior was evaluated through fire propagation speed, flame length (and their respective reduction rates) and the fuel material remaining and consumed. For all the retardants, the increase of volumes of the syrup promoted reduction of fire behavior variables, being recommended an application of syrup equivalent to 2.0 L m-2. The efficiencies of the Phos-Chek WD881® and of Hold Fire® presented increasing linear models with increased concentration improved retarder efficacy, however, the Nutrigel® presented efficiency with quadratic response to increased concentrations. The ideal concentration varied according to the product, recommended 1.0 mL L-1; 1.5 mL L-1; 0.0060 g L-1 for Phos-Chek®, Hold Fire® and Nutrigel®, respectively.