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Testing Your Soil: Why and How

Why have your soil tested?

Applying the wrong kinds of fertilizer can harm your crops and be a costly waste of money.  It can also affect our coastal waters and drinking water by washing into streams or leaching into groundwater.   Also, failing to correct soil problems or apply enough of the right types of fertilizer to your crops can result in poor yields and wasted effort.

Have your soil tested:

  • To find out if there are unseen problems
  • To find out if you should add fertilizer
  • To find out what kind of fertilizer you should use
  • To find out how much fertilizer you should apply

Basic Soil Analysis provides information about the pH of the soil, which tells you how acidic or alkaline your soil is, and about the available nutrient levels in the soil.

Specialized Soil Analysis can provide information on soil salinity, Nitrogen levels, organic Carbon levels, and micronutrient levels. You can also request testing for Aluminum levels or the presence of heavy metal contamination. Finally, you can test the particle size distribution which indicates the proportion of sand, silt and clay particles in your soil.

How do I Take a Soil Sample?

For complete directions, consult the CTAHR publication “Testing Your Soil: Why and How to Take a Soil-Test Sample” at the following link.

http://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-9.pdf

  • Bring in 2 cups of soil in a zip lock bag
  • If you have different soil types in different areas, bring in separate samples
  • Bring a sample from the top 4 inches for lawn, from the top 8 inches for tilled fields or garden plots,  and two separate samples of the top 8 inches AND the 8 inch to 24 inch zone for tree crops.

The Agricultural Diagnostic Service Center charges a small fee for soil analysis. Bring your sample to the Cooperative Extension Service at 875 Komohana Street in Hilo. Copies of the fee schedule are available at the CES office or they can be found online at the following link.

http://www.ctahr.hawaii.edu/Site/ADSC.aspx

The results of analysis will be sent to you by mail, along with an interpretation.

Kendal Lyon, Hawaii Island Master Gardeners