Evaluating Garden Soil
On this page find information about the nutrients plants need to grow and how to test garden soils for both nutrients and its acid-alkaline balance, including:
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- Sources, services, and do-it-yourself kits for performing garden soil testing.
- A step-by-step demonstration of how to collect a representative sample of soil from your garden.
- A step-by-step demonstration of performing a soil test with a chemical-reagent test kit.
- The mineral and non-mineral components of good garden soil and their role in soil texture and water drainage.
About Soil Tests
Perform soil tests as needed to measure its rate of drainage, levels of nutrients available for plants, and pH, or acid-alkaline balance. They’re all factors that influence the growth of your vegetables.
Many nurseries and garden centers provide testing services or referrals to soil laboratories. They’ll help you assess your garden’s soil and recommend any necessary amendments. Some also offer reliable home test kits.
If you choose a soil laboratory, follow its detailed instructions on how to gather your soil sample. Protect it from contamination during gathering, handling and transport.
Step-By-Step Instructions
Collecting Samples and Testing Soils
To perform soil tests yourself at home, gather a garden trowel, gloves, a clean glass jar into which soil samples may be placed, distilled water, the soil test kit or laboratory instructions, and then follow these easy steps:
How to Test Garden Soil with a Soil Test Kit
Dig a hole at the planting site. Using a clean container, collect a small amount of soil from the hole’s side, 3–4 in. (75–100 mm) below the surface. For large gardens thoroughly mix soil from different locations to create a representative sample of the area, or evaluate each area separately.
Using part of the sample of moist soil, squeeze it in your fist, then open your hand. If it feels gritty and falls apart when poked with a finger, the soil contains excess sand. If it holds together, roll it between your forefinger and thumb to produce a cylinder-shaped rope of soil. If it breaks before reaching 1/2-in. (12-mm) long, the soil has ample silt or loam. If the soil reaches 1 in. (25 mm) or more before breaking, the soil contains excess clay.
Measure relative amounts of three soil nutrients—nitrogen, phosphorus, and potassium—using a home soil test kit. Follow package instructions, which vary according to the specific kit. Always use distilled water when testing soil.
Determine your soil’s acid-alkaline balance using the pH test in the soil test kit. Use distilled water and follow all the package instructions for best results.
Electronic meters also check soil pH. Verify the meter’s accuracy and calibration by testing cow’s milk—it should read in the range of 6.5–7.0 pH. Thoroughly clean the probe each time before using it to test a soil sample.