Extension Search / Soil Labs / Rhode Island

Soil Testing in Rhode Island

Rhode Island’s land-grant university doesn’t run a soil lab for the public, so samples go to a private lab. Extension says which tests to ask for, so your numbers match the state’s fertilizer guidelines.

Private Labs

Ask the lab for these tests:

Basic test
Organic matter

URI Master Gardener soil testing has more on sampling and reading results.

Test Methods

Ask the lab for:

Phosphorus: Modified Morgan. A weak extract used in the Northeast. It gives much lower numbers than Mehlich-3.
Potassium: Modified Morgan. A weak extract used in the Northeast. It gives much lower numbers than Mehlich-3.

UConn and UMass both run the Modified Morgan test.

Labs pull nutrients out of soil with different chemicals, and each one gives a different number for the same soil. 20 ppm on one test and 20 ppm on another don’t mean the same thing, so check which test your report used before you compare it to a chart.

Tests

Basic test. pH, phosphorus and potassium, usually with calcium and magnesium. Enough for most gardens and lawns.
Organic matter. How much organic matter the soil holds, which sets how much nitrogen it releases.

URI Master Gardeners test soil pH free from March through October.
For a full nutrient test, URI points to the UConn and UMass labs, which take mailed samples from Rhode Island.

Sources: [1] [2]

Sample Tips

Take 10 or more small cores across the area and mix them in a clean bucket. One spot tells you about one spot.
Sample gardens and lawns about 6 inches deep, below any mulch or thatch.
Keep beds that are grown differently, like a lawn and a vegetable garden, as separate samples.
Wait a couple of months after fertilizing or liming, so the test reads the soil and not the last bag.
Use the same lab and the same tests each time, so the numbers compare from year to year.

Your county Rhode Island Extension office can help you take the sample and read the report.

Results

Once the report comes back, type the numbers into the soil test calculator to see what to add for your bed or lawn. The soil test guide walks through each line of the report.

Other States

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