ABSTRACT
Citrus is grown throughout the world in tropical and subtropical climates. The crops are grown primarily in a belt between 40° N and 40° S latitude, except at high elevations. Minimum temperature is the limiting factor, though the killing effect varies with variety, rootstock, absolute minimum and its duration, and dormancy of trees. Citrus appears to require the same complement of essential nutrient elements as other fruit trees. Perhaps the most distinctive thing about the nutrition of citrus is the large number of deficiencies of nutrient elements that have appeared under intensive cultivation. Foliage symptoms of deficiencies of N, P, K, Ca, Mg, Mn, Zn, Cu, Fe, B and Mo have been recognized in the field as well as in artificial cultures. Nitrogen is the key element in citrus fertilization and has pronounced effects on the growth and appearance of the tree, fruit production and fruit quality. It is used more extensively than any other fertilizer ingredient in commercial production.
