Reunion _ a geologically recent volcanic island located in the Indian Ocean _ has soils with andiques characteristics. They are rich in organic matter, clay (80% of amorphous substances or allophans), chlorine and magnesium but have poor saturation rates, exch. K, and CEC. They produce dark-air-cured tobacco with poor burning properties. In these soils with stable structure and high permeability (K = 4 x 10ex-3 cm), chlorine is easily leached by over-irrigation. So, 8 irrigations of 100 mm (check : 6 of 50) increase the burning capacity of : 200% for lugs (15 vs. 3s), 130% for middle leaves (7 vs. 3 s), 50% for tips (3 vs. 2 s). Thus, yield (3.0 t/ha) and quality (95/120) are not decreased. Leaf contents of chlorine, magnesium, nitrogen and nicotine are reduced. Potassium is more easily absorbed. A high potassic fertilization on tobacco (up to 1200 K20/ha) has no effect upon its burning capacity. On the other hand, a post-effect trial of increasing doses of potash u pon preceding culture, made over a period of 4 years, has shown that : _ 1200 K20/ha/year on sugar cane (for 400 of exportations) raised exch. K from 0.5 to 3.3 meq; _ the growing of tobacco that followed (yield 3.5 t/ha and quality 105/120) showed noteworthy potassium contents and burning capacities : 7% and 18 s for lugs 5.5% and 10 s for middle leaves 4% and 4 s for tips.