Crop Response to Soil Acidity Factors in Ultisols and Oxisols: I. Tobacco

Abstract Yields of tobacco (Nicotiana tabacum L.) on three Ultisols in Puerto Rico increased with liming up to about pH 5.0. There was a highly significant inverse relationship between yield and exchangeable Al. Maximum yield was generally reached as exchangeable Al approached 0 and at base saturation values of around 60%. Yields on an Oxisol increased with liming to about the same pH and base saturation level, although only traces of exchangeable Al were found. Leaf analysis indicated that Mn toxicity was a probable factor in the Oxisol. Tobacco root growth, studied in one of the Ultisols, was directly affected by low soil pH. Al toxicity appeared to be the chief cause of restricted growth but Ca deficiency was a possible contributing factor.