Studies were made in 1982-1994 at the Experimental Station for tobacco in Voicesti, Vilcea, Rumania, using Oriental tobacco in crop rotation with organic, mineral and mixed fertilization. The cultivars and crop rotations for different periods were as follows: cv. Djebel 123 (oats-tobacco-corn-bean) for 1982-85; cv. Djebel M 83 (oats-tobacco-corn-corn) for 1986-89; and cv. Djebel 252 (oats-tobacco-corn-corn) for 1990-94. Fertilization with well-decomposed organic fertilizers, at rates of 5-15 t/ha increased yield considerably as compared to the non-fertilized check, and with better results than with chemical fertilizers. With a 4-year crop rotation, the yields of the non-fertilized check were quite high, 913 kg/ha cured leaf for cv. Djebel 123, 1115 kg/ha for cv. Djebel M 83 and 1078 kg/ha for cv. Djebel 252. Increasing rates of organic or mixed fertilizers did not degrade the quality of cured tobacco, the percentage of superior and class I tobacco being respectively, 23.8-30.1% and 42.6-48.0% for cv. Djebel 123, 11.2-30.1% and 42.6-60.8% for cv. Djebel M83 and 11.1-23.1% and 46.2-52.6% for cv. Djebel 252. After 12 years of experimentation, the 4-year crop rotation visibly improved the alluvial soil of Voicesti, the non-fertilized variant showing high enzymatic activity. The chemical composition of the unfermented tobacco revealed a correlation between the low values of analysed reference points at small doses of fertilizers and higher values at higher doses and for low quality grades. However we do not consider that higher values indicate a worsening of the chemical composition related to organic or mixed fertilization.