- Describe how plants use N, P, and K
- Perform basic soil tests
When we created the flagship Edible Learning Lab in Buffalo, WY we thought we hit the lottery when the City graciously gave us two front end loader buckets full of top soil. It was relatively clean, not many root balls, rocks, or other undesirables.
We hauled the soil in 5-gallon buckets from the mound in the parking lot to the raised planters in the basement. It took 2 days. And our planters looked amazing! But after the first watering the soil compacted and formed a crust on the surface. We noticed just how fine the composition was so we set out during one class to analyze the composition and test the nutrient levels.
The soil lacked any discernible organic matter and the nutrient tests were disappointing. Nitrogen levels were fine, but both potassium and phosphorus were depleted.
The class added vermiculite and perlite for structure, mixed in a few gallons of coffee grounds from our local coffee shop, and tossed in a thin layer of compost. We retested and all levels are much better. It will be an ongoing process, building and testing, and something that the Students can now do with very little guidance.
Tools & Materials
- Soil testing kit
- Soil samples
Introduction (10 minutes)
Begin the lesson with a review of how plants use nitrogen, phosphorus, and potassium. Explain the importance of these nutrients for plant development and where it comes from.
Activity (20 minutes)
As a class, perform tests to determine pH, nitrogen, phosphorus, and potassium levels. Have the Students gather the samples and follow the instructions included with your soil testing kit. Record the findings.
Discussion (10 minutes)
What can we do to increase the nutrient levels? Why should we test samples from different locations in the planters? Why should we test each planter and not just one?
Assessment (5 minutes)
Use the following questions to assess the Students before and after the lesson. Tally the responses of the group in the Assessment Tracking Log for comparison:
- By a show of hands, how many of you have ever tested soil before?
- Now that you know how to test soil, how many of you think you could do it yourself?
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