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.
Leaf analysis will help determine if potassium fertilizer applications are needed. Mild potassium deficiency is similar to nitrogen deficiency, causing yellowish-green leaves. A severe deficiency will cause foliage necrosis, especially with scorched leaf margins, similar to soil salt build-up symptoms. Apply 150-200 lb of potassium per acre every other year if a deficiency occurs. Although no specific research has been conducted, it is believed potassium and phosphorus fertilizers can be soil-incorporated before planting at a rate of about 200 lb per acre.