If the rate of application is insufficient, as indicated by heavy fruit set and by tree performance, additional fertilizer may be applied. However, application of nitrogen after the middle of July is not recommended. Late applications can result in poor fruit color, in prolonged growth into the Fall, and an increased susceptibility to winter injury. Phosphorus Phosphorus is of importance in plant growth as a catalyzing agent in plant metabolic reactions. Its presence is necessary to permit the plant processes to utilize nitrogen.
Seed development is dependent on the element.
Failure of seeds to set often results in abortion of the young fruit and in misshapen fruit. Phosphorus is directly needed in grass growth. Soil levels less than 100 lbs. 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.