Effects of slash burning and fertilizer application on Eucalyptus grandis replanting in sandy soils of northeastern Entre Ríos.

The rate of clearcut of Eucalyptus grandis plantations in northeastern Entre Ríos surpasses 5,000 ha per year. Most of these areas are tended for a 2nd or 3rd rotation through their coppice. Replanting with improved genetic material, however, is an alternative for improving productivity. Slash disposal after harvesting constitutes a problem with no easy solution; slash burning is frequent and facilitates the replanting. This paper presents the results of two trials on eucalypt replanting; one compares the growth of eucalypt on two sites where the slash was burned and with the slash left in windrows. Diameter and basal area growth in the plots where the slash was windrowed were superior to the plots with the slash burned at age 3 yr; the burned plots also had a high defoliation after a long dry period. In the second experiment, the site was burned and a fertilizer trial was established after the replanting. A significant response to diammonium phosphate was found, with the fertilized plots growing 40% more in basal area than the control (5.60 vs. 3.96 m2.ha-1). The burning of the slash has potential negative effects on the soils and should be avoided in sandy soils; fertilization at time of planting may counteract these effects but long term studies are needed in order to evaluate the effects of slash burning plus replanting on the sites of the region.

Keywords: replanting, E. grandis, slash burning, fertilization.