Extension Search / Soil Labs / Colorado
Colorado State University Soil, Water and Plant Testing Laboratory
Colorado State University runs Colorado’s public soil testing program. Send a soil sample and you get back your pH and nutrient levels, and what each number means for your plants.
Lab Details
Colorado State University
Denver, Colorado
- Basic test
- Organic matter
- Nitrate
- Salts
- Micronutrients
- Texture
- CEC
- Lead and metals
Results take 7 to 10 business days after the lab gets the sample.
Open the lab's site for fees, forms and the mailing address.
Test Methods
This lab uses:
- Phosphorus: AB-DTPA. One extract for phosphorus, potassium, nitrate and micronutrients, used on alkaline Western soils.
- Potassium: AB-DTPA. One extract for phosphorus, potassium, nitrate and micronutrients, used on alkaline Western soils.
- Micronutrients: AB-DTPA. One extract for phosphorus, potassium, nitrate and micronutrients, used on alkaline Western soils.
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.
- Nitrate. Nitrate nitrogen in the soil now. Most useful in dry climates, where it carries over winter.
- Salts. Soluble salts (EC), and sodium where salt or poor drainage is a problem.
- Micronutrients. Zinc, iron, manganese and copper, sometimes boron.
- Texture. Sand, silt and clay, which sets how fast water drains and how much the soil holds.
- CEC. Cation exchange capacity: how many nutrients the soil can hold on to.
- Lead and metals. Lead and other metals, worth testing in old yards and near old buildings.
- Takes samples from homeowners, farmers, landscapers and consultants.
- Use the horticulture form for lawns, gardens and trees, and the crop form for field crops. The lab won't run a sample sent on an old form.
- Mail the sample or drop it off in Denver, Monday to Friday. Pay when you submit.
- County Extension offices have sample bags and tools and can help you read the results.
Sources: [1] [2] [3]
Not Tested
- Herbicide or pesticide residue
- Plant disease or insect diagnosis
Out of State
The lab’s site doesn’t say whether it takes samples from other states. Ask before sending one.
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 Colorado Extension office can help you take the sample and read the report.
Results
Other States
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