Introduction to Soils 1 What is soil Defined

Introduction to Soils 1

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 2

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 3

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. 4

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 microorganisms. 5

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

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. 7

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. 8

List the 5 factors responsible for soil development. 1. Parent material 2. Climate 3. Variation in the earth’s surface (topography) 4. Plant & animal life 5. Time 9

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 10

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 11

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

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

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 14

Plants use soil A. Anchorage – roots B. Water – absorbed through roots C. 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 15

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 16

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

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 18