Eficácia dos herbicidas imazapic e amicarbazone aplicado em diferentes quantidades de palha de cana-de-açúcar para o controle de plantas daninhas

Abstract

The straw left on the soil surface after the sugarcane mechanical harvest affects directly the weed infestation, due to, among others, the limitation of temperature variation on the seed bank, the formation of a physical barrier which enables weed emergence, and the possible allelopathic effect of the sugarcane straw. On the other hand, the straw also works as a barrier to the herbicide until it is leached into the soil. The objective of this study was to test the effect of herbicides amicarbazone and imazapic applied on different amounts of straw for the control of Luffa aegyptiaca , Ipomoea hederifolia and Bidens pilosa . Two herbicides - amicarbazone and imazapic were tested at three different rates: 1008 g a.i. ha -1 , 1260 g a.i. ha -1 and 1512 g a.i. ha -1 of amicarbazone, and 123.2 g a.i. ha -1 , 154 g a.i. ha -1 and 184.8 g a.i. ha -1 of imazapic, combined with the following amounts of straw: 6 t ha -1 , 8 t ha -1 , 10 t ha -1 and 12 t ha -1 , for both herbicides. The effectiveness of the control was evaluated until 120 days after the date of application. For the species Luffa aegyptiaca , the herbicide imazapic provided an efficient control during the 120 days of evaluation. This species growth showed a positive correlation with the amount of straw on the soil surface. The herbicide amicarbazone effectively controlled Luffa aegyptiaca at all doses, even when associated with higher amounts of sugarcane straw, where this species had a greater development. For the species Ipomoea hederifolia , both herbicides amicarbazone and imazapic showed satisfying control at all doses during the first 120 days, showing no statistical differences between the factors studied. For the species Bidens pilosa , all three doses, associated with all four amounts of straw, for both herbicides, showed above 95% of control in all assessments, with no statistical differences between the treatments.