Soil Testing



Students will understand how to analyze a soil test. Students will be able to amend soil according to soil test results. Students will be able to identify the major elements in the soil and the significance of each element, as well as the relationship between elements.


What is soil? Why is soil health important? What is balanced soil?


Soil testing materials, Soil test results, Amendments, Measuring tape, Scale, Paper cups, Cultivators


Activity 1: Soil Test Analysis


Review soil knowledge. Ask students, “What is balanced soil? What does it mean to have healthy soil? Elements in the soil

Students identify main elements (beyond NPK!). Make list on board Connection between plants and soil? -Bacteria!

Discussion: “Why is healthy soil important?”- Human health. Introduce William Albrecht – he made the connection between healthy soil and healthy people. This was a radical idea!Explain “nutrient density” Global warming/Climate change -Carbon sequestered in the soil: organic matter dictates how much water the soil can take in, and how much Carbon the soil can hold.

Explain that soil samples were collected from the school garden and were sent to be analyzed. We have the results, and we are going to explore them together and figure out what we need to do to make our garden grow the best food for our school!

Ask students, “how do we know how much we can amend the soil/how much fertilizer we can add? Is there such a thing as too much fertilizer?”-Gas tank analogy- Soil percolation dictates how much it can hold

Activity: In small groups, students analyze the soil test results. (The ideal levels for each element should be listed on the test. If not, post the ideal levels on the board) In their journals, students respond to the following questions:

Which elements are too high? (Discuss the issue of phosphorus on the island.) What can we do to lower levels of certain elements? Which elements are too low? Find relationships between elements (do you see any patterns when one element is high another is low and vice versa?)

Calcium and Boron, Sulfur and Magnesium, Potassium and Calcium

Introduce cations How do we amend these? What can we use as fertilizers? Are there other ways to amend the soil? (Refer to cover cropping lesson and/or compost tea lesson, if possible)

Epsom Salts = Mag Sulfate, Borax = Boron, Lime for acidic soil, Kelp meal = micronutrients, Sea salt = micronutrients

What about the micronutrients? Explain that there are 60-90 micronutrients that we also have to pay attention to – it’s not just about N, P, and K! Where can we find most of these nutrients? Hint: it’s surrounding the island (salt water)

Activity 2: Garden Bed Amendments


Introduce the history of New England soil – pH levels and acid rain. Ask students to list plants that like acidic soil. “Do the vegetables in our school garden like acidic soil? How can we balance the pH?”


Explain to students that it is their job to figure out how to make the soil in the garden beds the best it can be, to grow the best food for the school. Break students into small groups and assign each group a different area/bed. Hand out results from each area. In order to figure out how much of each amendment they are going to need, students must first do the math:

     -Area of bed  

     -Rate per acre of each amendment (usually ton/acre)  

     -There are 43,560 sq feet in an acre  

     -2,000 lbs. in a ton  

Using this ratio, students find their amendment measurement:

2000 lbs/ 4,560 sq feet = x/ (your garden’s sq feet)

If lbs. is too large a measurement, convert to ounces using this measurement:

16 oz/1lb = x/(your garden’s boron lbs)

Students present their findings to the class.

Next, students measure the correct amount of each amendment for their bed, in paper cups.

Finally, students go out to the garden and scratch their fertilizer into the soil using cultivators.

Students record their amendments in their journals, and in the garden binder for future students to see what they’ve done.


Cover cropping lesson

Compost and Compost Tea lesson

Soil texture and percolation