Citrus is an important crop in Florida, which accounts for nearly 70% of the total U.S. production. Traditionally, citrus acreage was distributed predominantly in the central ridge area where the soils are mainly Entisols, characterized by deep and well-drained Vadose zone. However, due to successive freezes, citrus production has gradually moved south where the soils are Spodosols or Alfisols, which are generally shallow and poorly drained. Current recommendations on soil pH control and management of mineral nutrition for commercial citrus production were developed on the basis of studies conducted on deep, sandy ridge soils. With more highly diversified citrus production in recent years because of the move southward, it is necessary to take a critical look at existing production recommendations as basis to propose modifications and additional studies as needed.

On some rootstocks including Sour orange, citrus can grow and produce well on soils ranging in pH from 5.5 to 7.5. The current recommendation on target soil pH for citrus production is 6.0 and for most soils, and 6.5 for soils containing toxic amounts of Cu. Maintaining the soil at pH above neutrality can result in problems associated with micronutrient availability, particularly with trifoliate and trifoliate hybrid rootstocks. In addition, irrigation with high CaCO₃ groundwater causes further increase in soil pH. Many long-term ridge citrus groves evidence accumulation of soil and foliar-applied Cu. Although Cu toxicity can be alleviated by maintaining soil pH above 6.5, even the critical or threshold soil pH for minimizing Cu toxicity has not yet been established. Further research is also needed to evaluate the role of Ca in the alleviation of Cu toxicity, and to assess whether Ca amendments other than lime can also be effective. In this respect, gypsum may play a major role. However, further studies must be conducted to understand effects of gypsum-induced leaching of other cations, such as K and Mg, from topsoil on the tree growth and fruit production. With the availability of abundant gypsum in Florida, and the low Ca status of some virgin Florida soils, the use of gypsum for citrus production in situations where raising the soil pH is not necessary should be explored.

This review focuses on the soil pH, Ca, and Mg requirements for citrus. Particular emphasis is given to data gaps and the need for additional studies.