Soil is made up of tiny particles of rock, plant, and animal matter. Soil acidity can be expressed using the pH scale. The pH scale ranges from 0 to 14. Soils with pH above 7 are basic. Soils with pH below 7 are acidic. A soil with a pH of 7 is neither acidic nor basic, but is neutral. The pH and water absorption of soil help to determine which plants will grow well in it. The pH of soil helps to decide which minerals are available for plants. Most plants grow best in soil with a pH of 6.5. Erosion is controlled by how well the soil retains water. In this activity, you will measure the pH of soil and measure how well soil samples absorb water.


  • Measure the pH of soil samples.
  • Determine the amount of water retained by soil samples.
  • Compare soil samples.