The aim of this work was to evaluate different dormancy overcoming methods of weed seeds of cultivated pastures in the Amazon region. The following methods were studied: Thermal scarification in hot water (800C) for 4, 8 and 12 minutes; chemical scarification in sulfuric acid for 5, 10, 15 and 20 minutes and potassium nitrate in the concentrations of 0.1, 0.2 and 0.3%. The seeds that did not overcome dormancy in these methods were put to germinate in the presence of kinetin (20, 40, 60 and 80 ppm) and gibberelic acid ( 150, 300, 450 and 600 ppm). Germination was monitorated during fifteen days, with daily counting and elimination of germinated seeds. Thermal scarification in water was not a satisfactory procedure once it reduced germinability in relation to the control treatment. Scarification with sulfuric acid gave very good results. However, there were diferences according to the time of immersion. The seeds germination of Cassis occidentalis, Stachytarpheta cayennensis, and Hyptis mutabilis were affected by potassium nitrate. Effects on seed germination of H. mutabilis were the most expressive. Solanum crinitum seeds responsed positively only to the different levels of gibberelic acid reaching a high value of germination at 600 ppm.
Sulfuric acid; hot water; potassium nitrate; kinetin; gibberelic acid