A general recommendation for apple trees is listed in table 1. Ammonium sulfate is the nitrogen formulation most recommended for orchards in New Mexico because it acidifies the soil somewhat. Although temporary, this action can make available some minor elements for use by apple trees. Amount of N recommended for apple trees. Any formulation of nitrogen fertilizer is converted to ammonium, then to nitrate, before it is absorbed by the tree's root system.
Nitrates are water soluble and can be easily leached out in irrigation water.
The best way to apply nitrogen and other fertilizers is through drip irrigation, where nutrients are carried close to the root system and recommended rates can be evenly distributed throughout the season. Surface broadcast application of nitrogen and other nutrients, with subsequent soil incorporation by discing, will always have some losses, first through volatilization, then through leaching. Splitting fertilization rates throughout the year may prevent most leaching losses, but may not be practical. In many cases, apple trees' perennial root system permits absorption of enough nutrients from soil that would be deficient for annual or seed crops. Apple trees growing in sandy soils, however, usually require potassium applications.