Revista Brasileira De Herbicidas 2016; 15(1): 97-106

ISSUE Cover

Dynamics of preemergent herbicides in production systems with straw

DOI: 10.7824/rbh.v15i1.441

The use of production management systems with the implementation of cultures in the straw provides many benefits, including protection against soil erosion, increase in organic carbon content, increasing the microbial population, soil moisture conservation and emergence inhibition of some weeds. Given these changes, the preemergent herbicides used in the systems with straw are intercepted before reaching the ground and when leached from the straw they may present differences in their dynamics in the soil. It is important to consider the dynamics of herbicides both in the straw and in the soil, taking into consideration the straw origin, quantity and distribution, as well as the herbicides physicochemical characteristics and the intensity and the period without rain after application of the herbicide. All these factors determine the amount of the herbicide intercepted by straw and its behavior in the soil. Thus, the aim of this review is to understand the dynamic of preemergent herbicides applied in straw and soil in no-till systems, raw sugarcane and minimum tillage. The maintenance of straw on the ground can both intercept and retain the preemergent herbicides applied, reducing their ability to reach the straw layer and causing a reduction in weed control. The longer the time interval between the application and the occurrence of rain or irrigation, the lower the amount of herbicide leached to the soil. Therefore, in crops with soil covered with straw, herbicides that are less vulnerable to losses by volatilization and photodecomposition should preferably be used, in other words, herbicides with higher solubility, low vapor pressure and octanol-water partition coefficient.