Use a soil probe to test how well irrigation dispenses into your landscape. Photo: Courtesy University of Florida/Creative Commons

Take the Test: Use a Soil Probe

If you want to create a healthy, thriving landscape full of beautiful plants, you need to know how to use an important soil management tool: a soil probe. 

Irrigation is essential to keep your landscaping green and growing. But to do so, you need to know as much as possible about your soils. One way is to use the Jar Test.

You should also use a soil probe. A soil probe lets you determine a lot more information about the soils in your landscaping. It helps you learn whether your irrigation water is successfully reaching the roots of your plants, or even if it soaks in too deep past the reach of plant roots.  

Without a good picture of your soil profile, you can’t answer questions about effective irrigation. Variability across your landscape could result in different types of soils in different areas, or in soil layers extending different depths.  

A good soil probe will help you figure out when irrigation water has reached the right depth for landscaping plants. It is a simple process with the right tools. 

When your soil is moist, a soil probe should go into the ground easily. Your soil probe will stop when it hits hard, dry dirt and won’t go further.  

How Low Should Your Irrigation Go?  

If your probe stops, it could be hitting a rock, so you may want to reposition it a few inches away and try again. If you are confident you’ve just hit dry soil, put your fingers around the probe at the soil surface, and pull it out. Measure the depth in inches to learn how deep your irrigation penetrates the soil. 

To properly irrigate your plants, understand the depth of their roots. Trees send their roots much deeper into the soil than shrubs, and shrubs have deeper roots than bedding plants like annual and perennial flowers or vegetables.  

Most plants will do fine as long as the top foot of soil is filled with water when you irrigate. Shrubs should be irrigated to a depth of two feet, and trees irrigated to a depth of three feet.  

You can purchase a soil probe at any general hardware story or gardening center. A basic soil probe costs between $30 and $80, but there are high-tech probes costing up to $300.  

This article was inspired by the 71-page Sustainable Landscapes Program guidebook available at SustainableLandscapesSD.org. Hardcopies are available free of charge at the Water Authority’s headquarters, 4677 Overland Ave., Kearny Mesa. The Water Authority and its partners also offer other great resources for landscaping upgrades, including free WaterSmart classes at WaterSmartSD.org.