Weed suppression with brachiaria in soybean crop

Abstract

Several factors reduce crop yield, including weed occurrence, which can be suppressed by crop rotation. We aimed with this study to analyze the composition of the weedy community after one and three years of distinct crop successions. Soybean was annually planted between October and February in areas previously cropped with one of the following treatments: maize planted in rows spaced in 45 or 90 cm; intercropping maize + Brachiaria ruziziensis; B. ruziziensis alone; and cowpea. Evaluations were carried out 15 days after soybean emergence. After three years, treatments tended to be more infested compared to the first year; the most important weed species was B. pilosa, which after three years was partially substituted by L. nepetifolia and E. heterophylla. Higher diversity coefficients were associated to higher infestation levels because new weed species joined while older species were not completely suppressed. A. hybridus was the most persistent one, being present in both years. Brachiaria planted in the second crop highly contributed for lower weed occurrence in the following soybean crop, and corn planted in rows spaced in 90 cm and cowpea promoted increased weed occurrence.