Introduction to Soils

1. Introduction to Soils The most important natural resource around the earth!

2. What is soil? Defined as: • Mineral & Organic material that supports plant growth on the earth’s surface • Mixture of particles of rock, organic materials, living forms, air, water

3. What soil resources help in supporting life? • Oxygen: needed for adequate root growth • Temperature: soil absorbs heat from the sun – loses heat to atmosphere (plant growth and seed germination) • Water: plant growth • Carbon: organic matter • Nutrients: minerals

4. Briefly explain the process of soil origin. • All soil originated as rocks. • Powerful forces act on the rocks to break them down into smaller fragments. • Water penetrates the cracks in the rock and when it freezes the water acts as a wedge to split the rock.

5. Soil origin cont. • Rivers, glaciers, landslides and avalanches cause rock particles to grind against each other wearing them down. • Chemicals mix with water to further break the rocks down. • Plants began to grow in the weathered rocks and as they die, they add organic matter to the soil which attracts soil micro-organisms.

6. Soil origin cont. • When this happens, the soil is capable of supporting plant life and can then truly be called soil.

7. What does the term weathering mean? • Weathering is the processes that occur to break down rock into soil. This process includes water freezing, thawing, landslides, wind and chemical action.

8. What is parent material? • Rock material that has undergone some weathering and change, but not enough to be called true soil, as it is not capable of sustaining plant life.

9. List the 5 factors responsible for soil development. • Parent material • Climate • Variation in the earth’s surface (topography) • Plant & animal life • Time

10. Components of Soil • Mineral Matter: about 45% of soil (partially decomposed rock material (sand, silt, clay) • Organic Matter: about 5% of soil (partially decomposed plant & animal matter) • Air: about 25% of soil (constant fluctuation as soil is dry and wet) • Water: about 25% of soil

11. Water in the soil • Infiltration: process of water soaking into the soil • Percolation: water movement downward • Permeable: quality soil allows for both infiltration and percolation – then it is said to be permeable

12. Living Organisms in the soil • Forms of life: • Earthworms • Insects • Bacteria • Fungi • Other organisms

13. Bacteria & Fungi Jobs • Break down organic matter and release nutrients

14. Earthworm & other soil organism jobs • Improve soil tilth • Ease at which soil can be worked • Create openings in soil as they tunnel • Enhances drainage and improves air exchange

15. Plants use soil • Anchorage – roots • Water – absorbed through roots • Oxygen – all living organisms need oxygen -plants release oxygen during photosynthesis and consume oxygen during respiration -good soil aeration needed for below ground plant parts to get oxygen

16. Plants use soil cont. D. Nutrients – of the 16 essential nutrients for plant growth – 13 are obtained from the soil -root hairs absorb the nutrients dissolved in soil water

17. Soil uses in agriculture • Cropland • Grazing land • Forest • Water structures • Agriculture depends on soil to grow food, fiber, and ornamental plants.

18. Nonagricultural uses of soil • Recreation: playgrounds, sports fields, jogging paths, golf courses, parks, campgrounds • Foundations: buildings have to have solid base • Waste Disposal • Building materials