When is liming needed?

Most crops will produce satisfactory yields within a pH range of 5.5-7.5, though micronutrient deficiencies (except molybdenum) become more likely above pH 6.8. Some, such as soybeans and alfalfa, don't grow well below pH 6.0. Others, such as pineapple, rice, coffee, potatoes, sweet potatoes, and watermelon, are more tolerant of acid soils than other crops.