These data show that relatively small amounts of nutrients applied to the soil are removed by citrus fruit. The larger amounts of these nutrients tied up in plant parts, particularly those in the leaf tissue, are eventually returned to the soil. For the most part, phosphorus, calcium, magnesium, zinc, manganese, copper, and iron will be adsorbed by the soil particles and are not easily displaced from the soil. Conversely, these elements may not always be readily available to the plant. Availability of most of these cations to a plant is highly dependent upon soil hydrogen ion concentration. Nitrogen compounds, being water soluble, move readily in the soil and are quite easily leached out, usually in the form of nitrates, although in some instances leaching losses of ammonium have been reported. It is imperative that nutrients be applied only as needed, since larger applications may be considered as “soil-polluting,” and may find their way into underground water supplies used for human consumption.

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