Don’t Be Talkin’ Dirt About Your Soil!

What do people often say about the soil around their homes?  “I’ve got crummy dirt and can’t grow squat!”, “Horrible dirt!” , “it’s that crappy clay!”… and many other negative comments that I’m sure you can imagine.  I don’t deny that soil characteristics can be a challenging issue.  But understanding what we are working with can improve our experiences in these planting situations.

In my last blog “Happy Hour For Trees”, you may have observed the diagram on the movement of water through different soil types.  In the table below, I’ve described the physical, chemical, and biological, soil properties, and management guidelines.

Soil Primer

There is not enough room to fully expound on this subject.  However, learning about soil basics can aid any horticultural enthusiast in managing their plants.

In general, clay (the most commonly disliked and misunderstood) can be a good soil due to its ability to hold water and minerals, yet it has poor drainage.  Clay needs less irrigation and fertilization than coarser soil types.  Sandy and silty soils require more frequent irrigation and fertilization since they can drain quickly and leach minerals.  Loamy soils are a combination of all soil particles and have some of the best characteristics.

The soil triangle above illustrates how different particles (sand, silt, and clay) are naturally found in a sample, and classify different soil types or textures. Note the loamy soils vary by the percent of sand, silt, and/or clay particles within that sample.  As the percentage of each particle type increases or moves toward each apex of the triangle, its characteristics become more dominant in the sample.

We know that roots require oxygen and moisture to grow, which are held in pore spaces between soil particles.  Macropores hold oxygen (for respiration) and micropores hold water.  If soil is compacted, the pore spaces are crushed, thus reducing available oxygen and moisture to roots.  If poorly drained soils are overwatered and saturated, particularly in clay, oxygen is displaced by the water, and roots die (from anaerobic respiration).  Newly planted trees are commonly killed by overwatering and soil saturation.  Too much water also invites fatal pathogens due to the high moisture environment conducive to root disease.  This can also lead to pest infestation that can finish off a stressed tree.

Easy to use tool & test

To assess your soil texture and moisture, try out this easy to use tool.  With care, a 15” ship auger (can be longer or shorter) on a cordless 18-volt drill is a speedy assistant in analyzing some basic soil conditions.  A piece of cardboard is helpful when drilling into dry soils.

WARNING:

• Wear a glove on the hand that removes the soil from the auger (see below).
• Be careful of underground sprinklers, conduits, and anything else that can be damaged by a drill.
• Hold the drill firmly as it can twist your wrist if not careful.

A photo of the auger test. See video at end of blog for complete demonstration.

Place the tip of the auger on the soil surface and engage the trigger on the drill to the depth being tested.  Pull out the drill and place the the auger in the gloved hand while reversing the direction of the drill.  Soil will come off the drill into the gloved hand.  WARNING: A sharp drill can cut your gloved hand.  Be extremely careful!

Dump the small soil sample into the ungloved hand and feel for moisture and texture.  If there is no soil on the auger bit, then it is lower in moisture or may be dry.  Try using the cardboard by placing it on the ground and drilling through the cardboard and then into the soil.  A sample should move up the auger and onto the surface of the cardboard.  Dump that sample into the ungloved hand and add drops of water to determine the soil texture.

Gritty soil is sandy, sticky soil is clay, and a smooth texture indicates the presence of silt particles.  It is likely that your soil is a combination of these types.  A feel test can help you discern the dominant characteristic, but takes some practice.  This link may help you master the feel test.

Easy to do test

Here’s another easy experiment you can do to help determine how your soil drains.  The perk test requires a small hole, a few inches in diameter or greater, to the depth that you wish to test.  Fill the hole with water and watch to see how fast it drains.  Note that drainage can be variable throughout your property.

Irrigation frequency and how it is applied, should be based on the results of the perk test.  Quick drainage directs a need for more frequent irrigation, with greater water output, but for short periods of time.  Slow drainage directs a need for infrequent irrigation with a low output of water. Use a drip system or soaker hose that applies droplets of water for a longer period of time.

A photo of the perk test. See the video at the end of the blog for a complete demonstration of the perk test.

Monitoring moisture with a probe, auger, or shovel after watering, will be required to determine the irrigation frequency and application method that works best for your soil.  Also keep in mind that some trees adapt to the natural rainfall cycles and do not need year round water.  Get to know the characteristics your soil and the water needs of the plants in your landscape.

To have the best success in your landscape, learn about your soil and the needs of the trees and other plants.  Start focusing on proper management and you may stop talkin’ dirt about your soil!

How can I help you with your trees?

Treemendously yours,

Bill Spiewak

Auger Test Video

Perk Test Video

Soils Feel Test Video