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Thursday, December 6, 2012

The Truth About Deep Root Fertilization of Trees and Shrubs


Q. Is deep root fertilization a good way to fertilize our African sumac tree, purple sage bushes and the purple plum tree?  I’ve seen advertisements from some landscapers for this process.  


Where are the roots of trees and shrubs growing
in a lawn?
A. There is nothing special or magical about deep root fertilization from landscapers or done by yourself. If done properly, and many do not, the fertilizer is injected into the soil at the depth of the roots. This is usually only a few inches beneath the surface of the soil.

            Deep root fertilizer applications have made a name for themselves mostly where trees and large shrubs are growing in a lawn. By applying it beneath the surface of the lawn, high rates of fertilizer are applied without damaging or killing the lawn or causing the lawn to have dark green spots of tall grass where the fertilizer is injected. The rates of fertilizer applied is quite high so the “saltiness” of the fertilizer (all fertilizers are salts of some sort) would normally kill the grass if that fertilizer is applied directly to the lawn.

These are the brown spots in your lawn that will occur
if you drop fertilizer on one spot or place it too shallow
under the lawn. It should be 6 to 8 inches under the surface.
            Also, lawn grasses are fertilizer “hogs”. Because of their fibrous root system they take fertilizer, nitrogen in particular, easily and quickly from the soil thus robbing it from deeper rooted trees and shrubs. By placing a complete fertilizer (one containing all three elements, nitrogen, phosphorus and potassium) several inches beneath the soil surface, it places the slower moving phosphorus and potassium right at where the roots are feeding.

            Commercial companies will usually use a liquid fertilizer and inject it with what is called a “soil needle” or deep root feeder. This is a probe that is connected to a tank on the back of a truck containing a fertilizer solution. A hose comes from the tank through a pump and, under high pressure, the liquid fertilizer is injected into the soil.

Granular fertilizer placed next to a bubbler in wood mulch so
the fertilizer will be moved to the roots by the water
coming from the bubbler.
            Real fancy units will allow the operator to squeeze the handle on the injector (a probe with holes in it to allow the fertilizer solution to injected into the ground) and inject a precise amount of fertilizer solution with each injection. The operator can inject the soil in dozens of places under the tree very quickly an be on his or her way.

            You will know if they are doing it correctly by how deeply they push the injector. If they push it too deeply, the fertilizer will be placed beyond the plant roots and a large amount will be wasted. If they don’t push it deep enough and it is in a lawn, then you may have burn spots in the lawn. Burn spots are usually less of a problem in the winter months.

            You can do deep root fertilize your own trees and shrubs by using tree and shrub fertilizer stakes and pounding them into the soil beneath the soil surface a few inches. You can also do it by irrigating the lawn and, while the soil is still moist, pushing a shovel into the soil in spacings about two feet apart under the canopy.

Fertilizer stake. The plastic cap is placed over the fertilizer
stake so that it does not shatter when pounded into the
wet soil under a tree near the source of water.
            The shovel is pushed into the soil all the way, pushed forward so that the slit cut by the shovel is open, and dropping some fertilizer into the open slit. You then pull the shovel out and push the slit closed with your foot. Irrigate immediately after you are finished.

            If your trees are in a desert landscape with drip irrigation then the whole idea of deep root fertilizer comes into question. When trees and shrubs are watered by drip irrigation then I would question whether deep root fertilizer applications are necessary. All the fertilizer will be “pushed” by watering from the drip emitters.

            Roots of trees and shrubs in a rock or desert landscape will not grow like they would in a lawn. Instead, with drip irrigation, roots grow profusely near the emitters and do not go “searching” for water or grow toward water. They are not psychics.

            With drip emitters is best to drop your fertilizer in slits next to the emitters or use tree fertilizer stakes at the emitters.

12 comments:

  1. Please get Fukuoka's books. Why are you fertilizing something you put in your mouth with chemical fertilizers? The whole point of growing your own food is to avoid chemicals in your food. Trees, if watered properly (see the other post I made) do not need to have deep fertilization. Do trees in the forest get fertilized? No. Are they healthy? Most all are. Keep them mulched well with straw and hay; water infrequently but deeply. Mimic the forest environment. I have 37 fruit trees and not one gets fertilized other than duck poop in the spring. But they all are mulched well and that breaks down and creates a beautiful ecosystem for your trees - full of lovely beneficial microorganisms. Let Nature do the work - Nature knows much more than we do what each beautiful living plant needs. Mankind always has to be thinking they know more. They don't.

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  2. trees in the forest have tons of organic matter breaking down into nutrients leaves (leaf compost) sticks , decaying trees ect..Its a great theory to as you say "mimic mother nature" however an inch or 2 of mulch will not supply enough nutrients for trees

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  3. I visited the link you gave me above because I don't know who they are. They say they are industry professionals and have certified arborists. Professionals like this will be able to diagnose what the problems might be and either tell you how to correct it yourself or do it for you. People like this you pay for their knowledge and experience. It is up to you whether you want them to do it or do it yourself. Sometimes they have access to treatments that you do not have or techniques that you don't know how to do. Professionals like this should be able to figure out what what the problem is with your tree and tell you how to fix it or fix it themselves.

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  4. Fertilizer solution, duck poop, natural decay, and your own body, is all chemicals. The molicules are the same. Nature doesn't care.

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    Replies
    1. Do you take a Multivitamin. I do. Most people do. it Just like you or I, your tree and shrubs will benefit from nutrients that may be lacking in its diet.

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    2. deep root for sure help newly planted tree after little eastablishing root system in a new landscape area where soil condition is different than its orignal place as nutrient help to permote eco system in close climate

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  5. I think that deep fertilization is something that I should look into. My plants have really needed help the past few summers, and extra fertilization might do it. However, I might also try some tree injections. http://www.schulhofftlc.com/tree-shrub-care/tree-injections/

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  6. We found this article very informative. We have recently added this to our collection of services. We live in an area that is part of an ancient esker so the soil tends to be rocky. Trees need all the help they can get. What's good for the environment is good for all of us! Thanks for a great article.

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  7. when you using this method of fertilization, what should be the concentration of the fertilizer applied? Is it applied directly in granular form or applied after dilution. Otherwise wont the feeder roots burn?

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    Replies
    1. The fertilizer is added directly in concentrated form. There is a high concentration where it is applied but is diluted quickly as it spreads from this point and pushed in every direction by applied water. Similar principle as tree roots growing in a sewer line or septic tank. But yes if you use a quick release fertilizer of any kind, organic or conventional, it will burn the roots in a small area where it is applied. Thats why I included the picture of the brown spot in the lawn.

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    2. The fertilizer is added directly in concentrated form. There is a high concentration where it is applied but is diluted quickly as it spreads from this point and pushed in every direction by applied water. Similar principle as tree roots growing in a sewer line or septic tank. But yes if you use a quick release fertilizer of any kind, organic or conventional, it will burn the roots in a small area where it is applied. Thats why I included the picture of the brown spot in the lawn.

      Delete