Effect of Tillage Intensity on Herbicide Efficacy and Eucalyptus spp. Productivity

Abstract

Weed interference in Eucalyptus must be eliminated early before treetop closure. In Uruguay, weed control in the planting rows is done with preemergent herbicides. This practice, that is performed in conjunction with rigorous soil preparation to ensure herbicide effectiveness, entails high production costs and erosion risks. We studied the effect of the type of within-row tillage (1) one pass of a heavy offset disk harrow, 2) two offset disk passes including a tooth harrow in the second pass, and 3) the same treatment followed by mounding of the rows) on preemergent herbicide efficacy and growth of Eucalyptus (a hybrid clone of Eucalyptus grandis x Eucalyptus globules). The herbicides evaluated were: oxifluorfen 240 g/ha; oxifluorfen 480 g/ha; isoxaflutole 150 g/ha; sulfentrazone 300 g/ha; sulfentrazone 400 g/ha; diclosulam 42 g/ha + 1800 acetochlor g/ha; acetochlor 1800 g/ha; oxifluorfen 240 g/ha + acetochlor 1800 g/ha. There was no interaction between preemergent herbicide effectiveness and tillage on total weed cover. The best treatments for selective weed control on the Eucalyptus grandis x Eucalyptus globulus hybrid clone were isoxaflutole (150g/ha) and oxifluorfen (240g/ha) + acetochlor (1800g/ha).