The topic of tree fertilization can be a controversial one. I personally have been on both sides of the fence on this debate which tends to have two primary views. One view is , “Trees do well in the woods and fertilization in your yard isn't needed”. The other view is that, “Trees in their natural environment recycle nutrients and your yard the soils and nutrient recycling are far from ideal”. The first view is one that I held before I spent many years studying trees and their responses to supplemental fertilization. I have developed an understanding for the second position after years of careful observation.
Your yard is a harsh place for trees, the soil has been compacted and modified to such an extent that it no longer bears much resemblance to the loamy duff of the forest floor. Forests are harsh environments, but they are places that trees are uniquely adapted to survive and thrive in. Trees exist in communities and grouping that balance nutrient requirements. Unseen battles for scarce nutrients take place in the forest and result in the forest you are looking at. The trees in your yard certainly would not exist as a community naturally in the woods. I no longer think fertilization is “ Snake Oil”. When correctly prescribed, formulated and correctly applied it is one of the most beneficial applications you can make to your trees.
The results of fertilization can only be seen over time in the growth and development of your landscape trees. Any gardener knows that to keep a plant alive you must water and fertilize it as needed and on a regular basis. If you don't they simply struggle and fade away. The basic N-P-K of fertilizer, nitrogen, phosphorous and potassium, come in a variety of formulations and forms. For trees it is important to have a substantial proportion of the nitrogen in a slow release form that is available to the tree on an extended basis.
There are a variety of ways to apply tree fertilization, broadcasting on the surface, drilling and placing granules into the soil, tree spikes, low pressure high volume hose end feeders, and high pressure liquid injection systems. Each has its advantages and disadvantages, having used all of them over the years I do recommend high pressure liquid injection as my method of choice. This method has the advantage of being able to quickly and accurately, both important considerations, deliver the correct blended fertilizer and soil amendments to the root zone. As we have discussed many times in the past most tree roots are in the upper 12 inches of the soil where oxygen and water are available. Soil fertility, micro nutrients,soil pH and root stimulation are only a few of the areas that can be addressed using the correctly formulated soil injection. The important issues of formulation, timing and proper application can be prescribed by an ISA Certified Arborist. If you want your trees to thrive and prosper, contact your ISA Certified Arborist.