Dynamic of herbicides applied in preemergence on sugarcane straw under different water regimes

Abstract

Maintenance of mulch on the soil surface can reduce the potential for weed infestations, and may affect transposition of the herbicides, the dynamics of wetting and washing the straw by rainwater. The study had as objectives evaluate the dynamics of the herbicides diuron, tebuthiuron and metribuzin in different water regimes with and without straw, and point out the main relationships between the presence or absence of straw removal of herbicides by rainwater and influence on the effectiveness of weed control. The experimental design was a completely randomized in factorial 6X3X2, with four replications, they were tested six levels for the rain factor (control, 0, 5, 10, 20 and 20 +20 mm), three herbicides (diuron 2000 g a.i. ha^-1), metribuzin (1920 g a.i. ha^-1) and tebuthiuron (1200 g a.i. ha^-1), and two quantities of straw (0 and 10 ton ha-1). One day after application, straw was removed from the vessels and Ipomoea grandifolia and Cucumis sativus species were sown in pots, evaluating the control at 15 and 30 and 10 and 21 days after application, respectively. Diuron was less effective in the treatments with straw compared to tebuthiuron and metribuzin. The straw significantly affected the weed control by herbicides in the absence of rain, and a rain of 20 mm was sufficient to cause leaching of the herbicides into the soil making them available for absorption by the plants and to promote excellent levels of control thereof.