Ground Up Approach

By Certified Arborist: Dane S. Shota

Dr. George Schmitz, my soil professor at California Polytechnic University Pomona said, "Everything starts from the soil, that is number one, everything else is secondary". In most instances that is what I see in the field where if a tree is diseased or with insect infestation the soil is too wet, dry, deficient or overly abundant of an element(s).

There are three types of tree growth: inhibited, normal and accelerated. When not enough water and fertilizer are given, tree growth is " inhibited". Insects and diseases would be prevalent and if severe, death of the trees would occur. " Normal" growth is when the right amount of fertilizer and water are given which allows the tree to "Harden off". Thus the tree is able to ward itself from most insects and diseases. If too much water and fertilizer were given, tree diseases would be prevalent again. When watering is severe, oxygen to the root is eliminated and root rot would occur and death may follow.

Trees, shrubs, and ground cover have different root depths and water requirements. Most often they are irrigated the same. That is when the problems can and most likely occur. Trees need to be watered deep and less often. Shrubs require less depth however more often. Ground covers are generally shallow rooted and require frequent shallow watering.

Approximately ninety-five percent or more of the decline of trees and plants are due to stress by not enough or too much watering. Watermark sensors measure the moisture by centibars; the lower the reading the wetter the soil is and the higher the reading the dryer the soil is. The range of tensiometric sensor ranges from 0 to 80 centibars. This is made for stationary use, protected by value boxes. Irrigation involves climate, shade, slope, soil texture, and plant water usage.

The watermark sensors can monitor all of these conditions. These sensors are the best that I found to monitor moisture to ensure the main aspect of plant health. Watermark moisture sensors have twice the range then tensiometers to be able to monitor the drier moistures in the desert like California.

My college professor Dr. Fred Roth had quoted a study involving the monitoring of tree roots. In this study tree roots were monitored at a one-foot level and another monitor was placed at a two feet level. Tests found that at the one foot and two feet level they were bringing up moisture at the same rate. This disproves the theory of only the first twelve inches called absorbing roots bring nutrients and water to the tree and anchorage roots which are located below the twelve inch mark that only provide anchorage. All existing roots provide necessary absorption of nutrient and water necessary for tree health. That is why it is so important that all roots at least through twenty-four inches should be monitored.

All roots should be moist at time of irrigation and then be able to dry out enough that roots are able to have gas exchange before root rot occurs.

Nursery trees that have just been transplanted have root balls the size of the box it has been in. All the roots contained in the boxes are essential for the tree’s life. Roots that encroach out of the box into the ground and then cut for removal for transport from the nursery to the job site have the optional of decline after planting which is a form of transplant shock.

When irrigating, if part of the root ball does not receive moisture, the tree is not using the maximum potential of the root ball the nursery had created and the nursery grown tree will experience a degree of stress.

Established trees have roots that extended from one to three times the drip line and root depths of twelve inches to three of more feet depending on soil texture, soil toxicities, deep or shallow watering, hard pan etc. At my house I had roots from a Melaleucaleucadendron at a seven feet level. The more roots a tree has the healthier it is, in fact inoculation of fungus and root giving the roots more surface area to absorb more water and nutrients a tree can procure on it’s own especially during drought years.

Fifteen parts per million of zinc will start to eliminate some of your micro flora such as beneficial mycorrhizae and bacteria. Thirty parts per million of zinc will eliminate almost all micro flora.

Certified Arborists recommend mycorrhizae with even testing soil to see if the soil in question is a good media for mycorrhizae.

In field grown trees where trees are planted and harvested as bare root I have noticed the differences of growth in the field. Even though these trees are propagated at the same time the size of the tree would vary from 3/8" to 1 ¼" diameter of the truck. Trees in sandy soil would grow more rapidly than in clay soil.

Yellowing of the leaves known as chlorosis is a lack a nutrient or nutrients that contribute to stunting growth. The range of pH can affect the lack of, normal, accelerated, or toxic amount of nutrients available to the tree.

I can go on and on about soil. In the 1600’s there is documentation on a relationship between the soil and the upper growth of trees. Now we have more technology in the way of soil laboratories and precise tools to monitor moisture since my first soil class. My soil teacher was right in most cases on saying, "Everything starts from the soil and everything else is secondary".

That is why the "Ground Up Approach" is a major key to Plant Health Care (PHC)