Introduction to Agriculture, Food, and Natural Resources 1

2 What’s in Soil? Introduction to Agriculture, Food, and Natural Resources Unit 4 – Lesson 4.1 Starting from the Ground Up

3 Soil is… The mineral and organic surface of the earth capable of supporting upland plants. Formed by the environment breaking down parent material over time.

4 Soil Components Soils are made of four main components.

5 Mineral Matter Includes rock and mineral fragments. Fragments are classified by size. Gravel Sand Silt Clay

6 Organic Matter Organic Matter includes things, such as: Plant roots Decaying leaves and other vegetative parts Animals: –Microorganisms (i.e., nematodes and fungi) –Insects (i.e., larva and worms) –Small mammals (i.e., gophers and moles)

7 Air Air provides oxygen for plant roots. Soil air is trapped in pores of the soil. Porosity is a term to define how much open space is available for air and water to be held in the soil.

8 Water Pore space in the soil can also be filled by water. Some soil water is available for plant use. Organic matter can hold more water because it creates pores and may even absorb water like a sponge.

9 Water If a soil has too many or large pores, water drains away and is not held for plant use. If a soil has no pores, the water does not filter through the soil and erosion can occur.

10 References Parker, R. (2010). Plant and soil science: Fundamentals and applications. Clifton Park, NY: Delmar.