Citrus such as Satsuma and lemon trees are heavy feeders. In order to produce a generous harvest they require ample amounts of nutrients released in a steady stream throughout their active season. For optimal results, do not fertilize a citrus tree during its first growing season with chemical fertilizers, because they can damage the root system.
Slow Release 10-10-10 Fertilizer
Citrus varieties require large amounts of nitrogen, phosphorus and potassium to bloom and produce fruit. An equal amount of these nutrients can be found in a standard balanced, or 10-10-10, fertilizer. Slow-releasing standard fertilizer is more beneficial for citrus as it ensures that the nitrogen does not wash below the root line. Standard fertilizer should be applied and watered in annually.
Citrus also requires special trace nutrients including magnesium, boron, copper and zinc. These trace elements are found in turf fertilizers. Similar to the balanced fertilizer, these nutrients should be applied and watered in annually. At the time of planting, consider adding mycorrhizal fungi to the soil. Mycorrhizal fungi attach to a plant's root system and enable the roots to gain more nutrients from the soil. This fungi tend to be absent from most urban soils. Finally, if the tree's soil is above a pH of 7, then iron must be added to the soil annually. Iron supplement tablets can be found at all garden stores.
Fish emulsion fertilizer contains all the necessary ingredients for proper fertilization of citrus. Because of the slower breakdown of organic fertilizers, fish emulsion must first be added at least one growing season before the tree is planted to ensure the soil has all the necessary nutrients at the time of transplant. Since organic fertilizers are gentler on a tree's root system, they can be added twice annually for an even more beneficial supplementation. Organic fertilization of citrus should occur when the tree is first budding and when the tree's harvest is complete.