Understanding the basic aspects of the biology of weeds may substantially improve the construction of more suitable strategies for their control, as well as help develop non-chemical control tools. This work aimed to evaluate the effect of sowing depth and soil cover on Alternanthera tenella emergence. Treatments consisted of a 7x2 factorial scheme, with seven depth levels (0, 1, 2, 3, 4, 5 and 10 cm) and two soil cover levels (with and without straw mulch). Straw mulch was provided by the aerial parts of black oat (Avena strigosa), simulating a soil cover equivalent to 2 t ha-1. Sowing was performed in PVC columns (50 seeds per column). Plant emergence was recorded daily up to 28 days after sowing. At the end of this period, total emergence percentage and emergence speed index (ESI) were calculated for each treatment. Emergence of A. tenella was affected by soil depth above which seeds were placed. Both in the presence and absence of black oat straw mulch, emergence was reduced in depths > 4 and 5 cm, respectively. There was no emergence for seeds placed at a 10-cm depth Seeds placed at soil surface presented emergence speed index equal to or higher than other depths, regardless of soil cover.
joyweed; seedbank; straw mulch