EFFECTS OF GLYPHOSATE ON GROWTH, YIELD AND WOOD QUALITY OF <em>EUCALYPTUS</em> <em>UROGRANDIS</em>

Abstract

This paper aimed to understand glyphosate behavior on Eucalyptus urograndis plants with different ages in the field. Understanding these effects is essential to improve weed management and plant protection in eucalypt, since glyphosate spraying is the cheapest, fastest, most efficient and most used weed control method. Glyphosate was sprayed at 1, 3, 5, 7 and 9 months after planting using 0, 36, 72, 144, 288 and 432 g acid equivalent (ae) of glyphosate ha^-1. One month after planting, glyphosate doses up to 72 g ae ha^-1 caused irreversible damage. Plants sprayed with glyphosate 5, 7 and 9 months after planting showed high recovery capacity. Accidental drift of glyphosate up to nine months after planting did not reduce the eucalypt growth parameters and wood volume. Only plants sprayed with higher doses (much larger than an accidental drift) showed reductions in wood volume. Thus, a dosage of almost twice more glyphosate is needed to cause reductions in the wood volume of older plants. However, trees sprayed at nine months after planting showed no reductions in productivity, even when sprayed with the higher dose of glyphosate. The spraying of glyphosate five months after planting did not affect the lignin content, holocellulose or basic density of the wood.