To cultivate tobacco successfully, it is important to have soil that is rich in specific nutrients. Option 1, calcareous matter, refers to soil that contains calcium carbonate. While this may have some benefits for plant growth, it is not specifically required for tobacco cultivation. Option 2, nitrogen, is a crucial nutrient for all plants, including tobacco. However, it is not the primary nutrient that makes the soil suitable for tobacco cultivation. Option 3, organic content, refers to the amount of organic matter present in the soil. Organic matter can provide nutrients and improve soil structure, but it is not the key factor for tobacco cultivation. Option 4, potash, is the correct answer. Potash, or potassium, is an essential nutrient for tobacco plants. It helps to regulate water movement, enzyme systems, and overall growth and development.