CROP ROTATION AND TILLAGE EFFECT ON THE WEED SEED BANK IN LOWLANDS

Abstract

On the rice crop, weed species more adapted to the production system appear in greater incidence in the area, thus, crop rotation can be an alternative to help reduce the weed seed bank. In this sense, the objective of this work was to evaluate the dynamics of the barnyardgrass (Echinochloa spp.) and alexandergrass (Urochloa plantaginea) seed banks in lowlands, in response to crop rotation and soil management. Rice, soybean and sorghum crops were used under conventional tillage and no-till system, cultivated in strips. Barnyardgrass and alexandergrass seed banks were evaluated after two years of cultivation, in the top 0-5 and 5-10 cm layers of soil. Barnyardgrass and alexandergrass seed bank densities were higher in continuous sorghum cultivation compared to rice cultivation. There was no difference of the seed bank between different soil layers, except for alexandergrassin continuous sorghum cultivation. The continuous sorghum cultivation in lowlands, without the use of a post-emergence herbicide, increases barnyardgrass and alexandergrassseed bank.