Johnsongrass is a plant with great aggressivity, beeing considered as a noxious weed. lts occurency has increased in soybean areas in Brazil, and this fact demands a broad knowledge related to its biology. With the mean purpose to study how to overcome its dormancy using chemical treatments, such as potassium nitrate and sulfuric acid, a laboratory and greenhouse experiments were conducted. In the experiment no. 1 the treatments were: seeds treated with potassium nitrate under the folIowing concentration of 0.5, 1.0 and 1.5% and scarification by concentrated sulfuric acid during periods of 1, 5, 10 and 15 minutes after which germination test was conducted. In the experiment no. 2 the evaluated treatments were: sulfuric acid scarification for 5, 10, 15, 20, 25 and 30 minutes after which seeds were germinated. ln the experiment no. 3 the treatments were the same as in the experiment no. 2 but seeds were germinated in plastic crispers with soil as substrate. From the results of experiment no. 1 it was observed that potassium nitrate didn?t improve the germination of Johnsongrass seed, but sulfuric acid overcame seed dormancy with best scarification period of 15 minutes. In the experiment no. 2 and 3 a limiting period for acid scarification was observed, which lies between 10 to 15 minutes, after which germination will be reduced.