How can we maintain healthy soil?
Soil science is very interesting. The complexities of ions, pH levels, nutrient uptake and soil horizon are indeed as diverse as they are complex. The health and micro-diversity of the soil greatly contributes to the health of trees. Soil maintenance is often overlooked when it comes to tree health and maintenance and the problems we see above ground are often linked to the important organisms, nutrients and water cycles below the surface. Soil science is a profession of its own but I would like to take a moment to identify a few helpful tools and practices homeowners can make to improve the soil and assist in tree health and vigor.
Whats pH all about?
pH means potential Hydrogen. It specifies how acidic or basic (alkalinity) a given solution is. Soils that measure low in pH are acidic (0-7) and those that measure high in pH have greater alkalinity (7-14). Most soils fall between 4.5-10. A pH with 7 is neutral. Once mixed with water a soil pH test will measure the hydrogen+ ion concentration within the soil sample. Once we know if a soil is either more acidic or basic we then can better understand what nutrients are available for uptake.
Nitrogen (N), Phosphorus (P), and Potassium (K) are some of the main macro nutrients that many trees and plants need to survive. However many micro nutrients are just as important to maintain the health and vigor of a tree. Even though your soil may have high levels of macro nutrients available, if the pH is reading high levels of acidity or alkalinity these nutrients may not be available for uptake or possibly the tree will uptake too much of this nutrient and instead have an adverse effect. Once you determine soil’s pH, consider conducting a soil nutrient test on macro nutrients such as N, P, K.
STEP ONE: Conduct a pH soil test.
STEP TWO: Conduct a Soil Nutrient test.
Companion Planting
Companion planting has many benefits to our landscapes. Companion planting is used to support benefits between plants such as fixing nitrogen, encouraging pollinators, promoting biological controls and maintaining diversity in our gardens and yards. There are many resources available on this topic. We encourage you to consider companion planting in your garden and landscape objectives. Find companion plants that support healthy micro-ecosystems. Each site is different so make sure the plant is suitable for the desired location. An example of a good companion plant is Comfrey Symphytum officinale. This medicinal herb has vigorous growth, favors well-draining but moist soils, full-to-part sun and is well suited for bringing nutrients deep in the soil closer to the surface.
Incorporating native trees and plants that are suited for the site can assist in building better soil texture and structure. Roots provide aeration and water to be trapped within the soil particles. Allowing plants and trees to take up nutrients.
As we build diversity in our landscapes we promote many biological controls against unwanted pests. When we have a landscape full of one species this is called mono-cropping. In the event of a disease or pest, the plants can be extremely vulnerable to attack. With diverse plants combating against pests and pathogens your landscapes and gardens are better equipped to face these attacks while maintaining health and vigor in the soil and in their companion plants.
Composting and Organic material
As tree workers we obviously find ourselves in peoples yards all across the city. One thing that we have noticed with clients that have landscapers who “clean” their yards weekly by removing every last leaf, needle or twig, will often as us “why does my tree look so sick”?
Trees and plants need organic material to thrive. When trees drop their leaves in the fall they are fertilizing the soil within the drip line. The richest soil horizon for growth is the “organic” horizon. So it’s no surprise that the best promoter of plant growth is the amount of organic material within the soil. The soil around Portland, Or is high in clay. Soils high in clay are difficult for root growth and proper water drainage. Organic material helps build a more suitable structure for available nutrients, water and air. We encourage and promote either building a compost bin or wheel to collect organic debris from your yard and allow the compost to fertilize your trees and plants throughout the year.
STEP THREE: Collect and spread compost to plants and trees.
The strength of soil is dependent on so many factors—some outside of our control—such as long periods of drought. Plants play an essential role in maintaining soil health. These few items listed above can have large impacts on building a healthy soil profile. In short, knowing the condition of your current soil structure and continually adding organic matter will improve and maintain your soil. So next time you start to see some wilting or discoloration on your tree remember to look down and start digging.
