The use of special forms of phosphorus under Pennsylvania orchard conditions has not been documented. It is preferred that applications before the trees are planted, be broadcast and turned under with the previous-crop. This aids in getting phosphorus down into the root z-one of the tree. Potassium Orchard soils low in potassium are rare. The relationship between soil test, tissue test and response of fruit trees to potassium fertilizer have not been adequately determined.
Potassium needs in an established orchard are best determined from leaf analysis.
Mg is too high. Low soil test values frequently are found on very sandy or shelly soils, but such test values usually do not indicate a need for applications of calcium or lime. Needs for calcium or lime are best determined by soil test. The acidity or alkalinity of a soil is measured in terms of RpH.S Fruit trees can be found growing well at pH values ranging from as low as pH 5.0 to as high as pH 8.0. In such soils, manganese can be very toxic to trees, particularly young Delicious apple trees.