Abstract Background: Studies of sorption and desorption of herbicides in soils are essential in predicting their transport, bioavailability, and transformation in the soil profile. These studies are also vital to predict the agronomic efficiency of the herbicides in controlling weeds. Objective: In this study, atrazine’s sorption and desorption kinetics were evaluated in samples composed of single and a mixture of horizons from the Red-Yellow Latosol profile. Methods: This was performed by the Batch equilibrium method, and the quantification was carried out using a High-performance liquid chromatography (HPLC). Results: Freundlich isotherms were adjusted appropriately to describe the atrazine sorption. The Kf values obtained varied between 0.188 and 2.592, and the Koc values ranged between 37.76 and 143.81, which corresponded to horizons C and A, respectively. The desorption was only possible to determine in horizon A. The other substrates presented low sorption, and the desorption of the remaining atrazine was not significant, therefore not adjusting to the Freundlich model. The organic matter (OM) was the main attribute to the atrazine sorption in the soil, presenting a high correlation with Kf and Koc values. In the horizon A samples, the Kfd value obtained in desorption was higher than the Kf obtained in sorption, which indicated a low desorption capacity and, therefore, low potential mobility of the herbicide in this soil horizon. Conclusions: It was concluded that the organic matter present in greater quantity in horizon A of the Red-Yellow Latosol has a crucial role in the dynamics of atrazine in the horizons of this soil.

Modern agriculture relies on the massive use of agrochemicals, including herbicides. Despite their effectiveness, a continuous use of herbicides sharing the same target has resulted in the selection of weed biotypes resistant to such chemicals. To cope with this problem, the development of new herbicides is an urgent requirement. In this work we applied the Active compound Derivatization Method (ADM) strategy to develop a new tetraoxane (5), derived from the synthetic auxin 2-(naphtalen-1-yl)acetic acid (NAA). Greenhouse bioassays showed that 5 caused chlorosis, necrosis and leaf epinasty in Cucumis sativa. Furthermore, this compound, at the concentration of 1.25 x 10-5 mol L-1, inhibited the growth of important weeds such as Bidens pilosa, Iponomea acuminate, Solanum americanum and Althernantera ficoidea. For some weeds, the compound effect was higher or comparable to those caused by commercial glyphosate and imazethapyr. In addition, degradation studies revealed that 5 is transformed into NAA. The results also showed that 5 could act as photosynthesis inhibitor and as an auxin herbicide. In summary, we have discovered a new compound that may be a useful lead for the development of a commercial herbicide.

Clomazone exhibits high water solubility, low sorption in soil colloids, and therefore can leach and contaminate deep layers of soil profile and groundwater. In this work, the effect of the incorporation of sugarcane bagasse biochar in leaching and bioavailability of clomazone in red latosol was evaluated. Soil samples amended with 1% (m/m) biochar were placed in different depths (0-1, 0-2.5 and 0-5 cm) on the top of polyvinyl chloride (PVC) columns filled with soil. Clomazone-based herbicide was applied, and rainfall was simulated on top of the columns. A validated chromatographic method, together with a greenhouse bioassay, were used to quantify and to evaluate the mobility and availability of clomazone along the columns. The incorporation of sugarcane bagasse biochar in the superficial layers at the column tops increased herbicide sorption, reduced its leaching and bioavailability in soil and scaled down the environmental risk of clomazone avoiding contamination of underground aquifer reservoirs.

Intercropping is a common practice among farmers in tropical regions of the world and has persisted for years, not only for traditional reasons, but also for certain advantages that helped in its ecological adaptation. In regard to low income farmers with small areas for cultivation, more attention should be given to the cost of production and better land management. Thus, the aim of this work was to determine the best intercropping system of cassava with other crops. The experiment was conducted in an area belonging to the cassava (Manihot esculenta) producers of the Planalto de Minas district in Diamantina, Minas Gerais State, Brazil. The treatments comprised cassava intercropped with maize, beans and dwarf pigeon pea, as well as controls with and without weeding. The dry mass of shoots for maize, beans and dwarf-pigeon pea was affected by the presence of cassava. The productivity of cassava was dependent on cultivar and the intercropped crop. The highest harvest indexes were observed when cassava was intercropped with maize. In a general way, intercropping with maize and beans showed the highest area equivalence indexes and are recommended for the cassava crop.

Intercalar cultivos es una práctica común entre los agricultores de las regiones tropicales del mundo, que ha persistido a lo largo de los años, no sólo por tradición, sino también por la búsqueda de las ventajas que han ayudado en su adaptación ecológica.Cuando se considera a agricultores con pequeñas propiedades de cultivo y bajos ingresos económicos, se debe poner más atención en los costos de producción y en el mejor aprovechamiento de la tierra. Así pues, el objetivo de este trabajo fue determinar el mejor sistema de intercalar la yuca con otros cultivos. El experimento se realizó en un área perteneciente a los productores de yuca (Manihot esculenta) del distrito de Planalto de Minas en Diamantina, Minas Gerais, Brasil. Los tratamientos consistieron en intercalar la yuca con maíz, frijoles y guisantes enano paloma, así como los controles con y sin deshierbe. La producción de materia seca de rebrote de maíz, frijoles y guisantes enano paloma se vio afectada por la presencia de yuca. La productividad de la yuca depende de la variedad utilizada y de los cultivos intercalados. Los mayores índices de cosecha se observaron cuando la yuca se intercaló con maíz. De forma general se puede afirmar que el cultivo de la yuca, intercalado con maíz y frijol, muestra los índices de equivalencia área más altos, siendo el más recomendado para el cultivo de la yuca.