Very sandy soils lacking sufficient clay and organic matter are quite prone to nutrient deficiency. Landscape plants in such soils often exhibit deficiency symptoms without a regular fertilizer maintenance program. Fertilizer application is likely to help newly planted trees and shrubs reach their landscape potential. Fertilizing also benefits trees and shrubs which have undergone partial or complete defoliation by insects and diseases, or stress caused by digging or trenching in the root zone. Appropriate fertilizer application may stimulate recovery from winter injury.
Soil tests can determine the levels of phosphorus and potassium in soils.
Very low readings of these two minerals may indicate the need to add these nutrients to a fertility program. In most cases, potassium and phosphorus reserves tend to be sufficient for woody plants- only a straight nitrogen fertilizer will be required. Research indicates that nitrogen may be the only nutrient which will cause a growth response in woody landscape plants. Many fertilizer formulations are available, but since woody plants generally respond only to nitrogen application, it would be appropriate to use formulations consisting only of nitrogen or ones in which nitrogen was the predominant mineral. Lawn fertilizers without weedkillers are acceptable for fertilizing woody landscape plants.