The relationship between straw and herbicide for controlling Ipomoea sp. in sugarcane ratoon

Background: A new agronomic management is used in sugarcane fields, due to the removal of part of the layer of straw on the soil surface for the cogeneration of energy, culminating in variable amounts of straw. Objective: The objective was to evaluate the population dynamics of weeds in different scenarios of straw removal; to evaluate the weed control and selectivity of sugarcane; to determine the amount of sugarcane straw that must remain in the soil to facilitate weed control in a sugarcane crop. Methods: The main treatments were the following straw amounts maintained on the soil surface: 0, 5, 10 and 15 Mg ha-1. The secondary treatments were: application of sulfentrazone + tebuthiuron and without herbicide. The research was conducted for two years. Results: The main weeds found were two morningglories, I. triloba and I. hederifolia. With the increase in the straw removed from the soil, the density and dry mass of the weeds rised. The control percentage was close to 100% and the sugarcane was selective for the herbicides used. For both crop years evaluated, the absence of straw and herbicides showed inferiority in sugarcane productivity. Conclusions: The sugarcane straw removal for the energy cogeneration industry would be feasible with the removal of 5 Mg ha-1 of straw on soil surface, maintaining a layer of at least 10 Mg ha-1.