How to Test Your Soil

Planting Bed Preparation

A soil test will tell you if the soil in your garden is rich or poor in minerals and nutrients/

Plants depend upon soil nutrients and moisture for growth. If the soil in your garden lacks nutrients, plants will grow poorly or die. The relative acidity or alkalinity affects how soil nutrients become available to plants.

You can test the soil in your garden yourself, or you can send it to a soil testing lab.

Home do-it-yourself soil-test kits test for soil pH (the relative acidity or alkalinity) and major soil nutrients–nitrogen, phosphorus, and potassium. DIY soil-testing kits do not test for micronutrients or organic matter content. The advantage of a DIY kit is that you can test individual beds and get immediate results.

Professional laboratory tests—from a commercial lab or from your state Extension Service–provide more information than home tests, usually pH, nitrogen, phosphorus, and potassium levels, values for secondary mineral elements and micronutrients, and also a report on organic matter in the soil. Professional lab tests cost more time and money than DIY tests.

How to Take a Soil Sample

Take a soil sample on a dry day. Use a clean trowel or spade or a soil sampling probe—a length of pipe with a sharp to pierce the soil.

  1. Dig a hole six to eight inches deep.
  2. Take a thin slice of soil about an inch thick from the straight side of the hole. Trim the slice into thirds along its length—use the center or inner slice for the test.
  3. You can test each planting bed or take half-dozen samples from around the garden equally distant apart. Mix the samples in a plastic bucket; take your sample from this mix. (If you know your garden has very different types of soil in different areas of the garden, test each section separately.)

How to Test the Soil

Home soil test kits commonly use pH-sensitive paper or film or water-soluble powder. Once you have a soil sample, add mineral-free distilled water to make a slurry then dip in the pH-sensitive paper or add a bit of your sample to the pH-sensitive powder (just follow the instructions that come with your soil test kit).

Compare the color of the paper or solution to those on the chart provided with the kit. Your soil will fall between a pH of 4.5 and 8.5. A chart with the kit will tell you if your soil requires amendments to change the pH or additional fertilizer for the plants you want to grow.

When to Test Your Soil

Test the soil periodically throughout the growing season. It is especially important to test before planting in Spring and when preparing your planting beds for the next season in Fall. If plants are not growing well, a soil test may tell you how you can help.

Related Articles on Soil Preparation:

Understanding Soil pH

Adjusting Soil pH

Vegetable Plant Nutrients: Sources and Deficiencies

Soil: Making the Kitchen Garden

How to Improve Clay Soil

Autumn Soil Care

Written by Stephen Albert

Stephen Albert is a horticulturist, master gardener, and certified nurseryman who has taught at the University of California for more than 25 years. He holds graduate degrees from the University of California and the University of Iowa. His books include Vegetable Garden Grower’s Guide, Vegetable Garden Almanac & Planner, Tomato Grower’s Answer Book, and Kitchen Garden Grower’s Guide. His Vegetable Garden Grower’s Masterclass is available online. has more than 10 million visitors each year.

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