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Crops Investigation #4

Goal:

The goal of this activity is to teach the students basic soil chemistry and to test for nutrients.

Objectives:

Students will be able to test for potassium, nitrogen, and phosphorus, and measure pH.

Standards Met:

Overview:

Soil nutrients are necessary for successful plant growth.  This activity examines the macronutrients available in local soils.  This information will be used in determining the "best" soil to farm.

Materials:

Resources:

Actions:

Prior to the lesson:

  1. Students will analyze the physical characteristics of their soil samples.
  2. Students will plot the location of their soil sample on a map of their county.

During the lesson:

  1. Have students make "soil tea" from their individual soil samples by placing approximately 15 mL of soil in 30 mL of water.  Stir well with spoons or popsicle sticks.  Allow this to stand for 30 minutes.  
  2. While the "soil tea" is seeping, conduct either a lecture or discussion of soil chemistry.  This should include the following information:  1) soils can be classified as topsoil, the first 8-10 inches, or subsoil, located beneath the topsoil.  2) Soil types are generally determined using physical properties and the proportion of sand, silt, and clay they contain.  What physical properties did we talk about in the last lesson?  What were the physical properties of your soils?  Which soil had the most clay?  Sand?  Silt? 3) Farmers, gardeners, and earth scientists are also interested in the nutrients contained in the topsoil.  These include macronutrients (nitrogen, phosphorous, potassium) and micronutrients (calcium, sulfur, boron, magnesium, iron, manganese, copper, and zinc).  What makes nutrients important?  How do you think they are used by plants? Soil composition varies by the amount and availability of these nutrients.  A soil with very good physical characteristics may not be good for growing things because it is deficient in a vital nutrient.  Which nutrients do you already know are important for crops?  Which nutrients do you think soils in our area might be deficient in? In addition to nutrients, we are also concerned about pH.  Who can explain pH to us?  How do you think pH affects plants? We will be looking at macronutrient content of our soils today.
  3. Have students don safety equipment:  aprons, gloves, and goggles.
  4. After the "soil tea" has seeped for 30 minutes, put students into their project groups and have each group test their soils for macronutrients.  This is done by filling the test side of each nutrient tester to the fill line, then adding the contents of the appropriate test capsule, placing the lid on, then shaking the tester until the capsule contents have dissolved in the soil tea.  Wait 5 minutes, and then "read" the results from each test.  This whole step (4 students testing 4 properties of 4 samples) should take 25-30 minutes to complete.
  5. Have students record their results in their science notebooks and on the classroom county maps (one map should be potassium, one phosphorous, one nitrogen, one pH).  Make sure they label their results on the county map with their initials. 
    6.  

Extensions:

  1. Conduct tests for micronutrients.
  2. Conduct tests for calcium content. 

Assessment:

Notebooks will be checked for completeness. Complete notebooks will receive 10 points. Incomplete notebooks will be downgraded according to the policies of individual classrooms.

Reflection:

Please write a reflection after you teach this lesson to help us make improvements. Reflections should be e-mailed to j.okeefe@moreheadstate.edu and c.wymer@moreheadstate.edu. If you also complete student reflections, please include these as well.