Fatores abióticos na germinação de sementes, fluxo de emergência de Echium plantagineum L. em diferentes sistemas de manejo

Abstract

Echium plantagineum, popularly known as the purple flower, is considered an annual weed, which infests crops and pastures in the fall, winter and spring periods. Considered an aggressive species of rapid growth, has high capacity competition being classified as a species difficult to control. In addition to presenting adaptation to different environmental conditions. In this sense, the objective was to evaluate the influence of abiotic factors on seed germination, emergence flow and soil seed bank in management systems, and to monitor the germination of seeds stored in different environments. Experiments were carried out in laboratory under controlled conditions to evaluate the effect of light qualities and dormancy overcoming, and influence of solutions with different aluminum concentrations and pH on seed germination. In the field, an experiment was conducted with four tillage systems, with no-tillage and tillage systems, both with and without control of E. plantagineum on ryegrass pasture, which evaluated the monthly emergency flow for 25 months and the soil seed bank. In addition, germination and viability of seeds stored in different environments for 12 months: in soil buried at 20 cm depth, cold chamber and ambient conditions in the laboratory were monitored. When dormancy was not overcome, light quality influenced germination, with higher germination occurring under red light incidence and lower germination in the absence of light. Overcoming dormancy the quality of light did not interfere with germination. It was verified that the presence of aluminum in the substrate presented toxic effect to seed germination, being smaller with the increase of aluminum concentrations. However, germination of E. plantagineum seeds was little affected by substrate pH and was not a limiting factor to germination. In the field experiment it was observed that the emergency flows were concentrated from January to April, with higher intensity in the no-tillage system without E. plantagineum control. The no-tillage system with control presented greater reduction of the soil seed bank, whereas the tillage systems distribute the seeds vertically in the soil profile, with seed bank feeding. Seed storage reduced germination after the fourth month of soil storage and increased dormant seeds. Given this, integrated management strategies such as no-till and presence of soil cover with crop residues, coupled with herbicide control can be efficient in the management of E. plantagineum and reduction of soil seed bank.