Systems of soil preparation and the control of perennial weeds in Brachiaria decumbens

The aim of this work was to study the influence of some soil preparation systems on weed population and vigor, and on the formation of the Brachiaria decumbens pasture. The treatments consisted of various combinations of disc ploughs, harrows (24 ") and levelling harrows. The best results for weed control and pasture establishment were those that reached the deeper soil layers, corresponding to the following implement combinations: ploughs + levelling harrows, ploughs + harrows, harrows + harrows, harrows + levelling harrows, or only harrows. Among the systems of deeper soil preparation, those that involved the use of the plough were slightly more efficient than the rest. The systems of superficial soil preparation with levelling harrow, or without soil preparation (no tillage) were not efficient in either weed control or pasture establishment. Differences among the results due to the soil preparation systems were evident for both weed species. Generally, B, bongardii was more sensitive to deeper soil preparation than R. martiana. The economic analysis of the soil preparation systems followed by one herbicide treatment showed that the systems which included at least one deep operation are more economic.