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Transcript
BELL RINGER 1.9.14 • What makes up soil? • What is topsoil (take a guess!)? • What is the average amount of topsoil (in inches)? • What is soil used for? (name two different reasons) 1 Introduction to Soil 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, gas (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 • Minerals: nutrients and physical makeup 4 Briefly explain the process of soil origin. • All soil originated as rocks. • Soils are formed by weathering of 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 microorganisms. 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. 1. Parent material 2. Climate 3. Variation in the earth’s surface (topography) 4. Plant & animal life 5. Time 10 11 Parent Material • Parent rock from which a soil is formed has a significant effect on its qualities. • Parent materials influence the formation of soils by their rates of weathering, the nutrients that they supply, and the particle sizes that they contain. • The less developed a soil is, the more influence that the parent material has on its characteristics. • Mineral particle size has a great effect on the properties of soil in the field. 12 Climate • Climate is a dominant factor in the formation of soils. • The major components of climate that affect soil are precipitation and temperature. • With low rainfall an accumulation of lime may occur ,so these soils are usually alkaline. • In areas of high rainfall there is intense weathering and leaching resulting in acid soils. 13 Climate continued • Erosion of sloping lands removes developing layers of soil and deposits them down slope. • Erosion, leaching and weathering are more intense and take place over a longer period each year in warm and humid areas. • Climate also has an indirect affect on soils by its action on vegetation. • Changes in temperature affect the rate of physical/chemical weathering. Rates of chemical reactions increase as temperature increases, if sufficient water is also present. 14 Topography • Topography (the lay of the land) influences drainage and runoff. • The profile on gentle slopes will be generally deeper, sustain more luxuriant vegetation, and contain more organic matter than soil profiles on steeper slopes. • In our hemisphere, mountains often affect the climate and in turn the soil. The western side of a mountain range often receive more rain and have more developed soil vs. the drier east side of a mountain. 15 Living Organisms • The activity of living plants and animals (macro and microorganisms) has major significance on the development of soil. • Microorganisms help develop soils by decomposing organic matter and forming weak acids that dissolve minerals faster than would pure water. • • Fibrous root systems of grasses have a distinctly different effect on soils than do the coarser roots of trees. • Lichens, which are a combination of algae and fungi, are often the first plants that grow on weathering rocks. 16 Time • It requires time, up to about a million years, to form soils. • Rocks like granite are extremely hard to decompose. Softer rocks such as limestone take less time. • As soils age they differentiate into defined profiles consisting of three different layers (A horizon, B horizon and C horizon). • Horizons tend to develop faster under humid, warm, and forested conditions. • A recognizable soil profile may develop in as few as 200 years or, under less favorable conditions, take several thousand years to develop. 17 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 18 Water in the soil • Infiltration: process of water soaking into the soil (surface downward) • Percolation: water movement downward through soil and rock (below the surface) • Permeable: quality of soil that allows for both infiltration and percolation – then it is said to be permeable 19 Living Organisms in the soil • Forms of life: – Earthworms – Insects – Bacteria – Fungi – Other organisms 20 Bacteria & Fungi Jobs • Break down organic matter and release nutrients 21 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 22 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 23 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 24 What is Topsoil? • Topsoil is the upper, outermost layer of soil, usually the top 2 inches (5.1 cm) to 8 inches (20 cm). It has the highest concentration of organic matter and microorganisms and is where most of the Earth’s biological soil activity occurs. 25 Importance? Commercial application? • Importance: Plants generally concentrate their roots in and obtain most of their nutrients from this layer. • Commercial application: A variety of soil mixtures are sold commercially as topsoil, usually for use in improving gardens and lawns. • Erosion: A major environmental concern known as topsoil erosion occurs when the topsoil layer is blown or washed away. Without topsoil, little plant life is possible. 26 Evaluation • When starting a gardening project, it is very crucial to check whether or not the soil is satisfactory. Following are the desired levels of Topsoil nutrients: Category Desired Results pH Level 5.8 to 6.2 Phosphorus (P) Index of 50 Potassium (K) Index of 50 Calcium (Ca%) 40-60 % Magnesium (Mg%) 8-10% Base saturation (BS%) 60%-80% 27 Soil uses in agriculture • • • • Cropland Grazing land Forest Water structures • Agriculture depends on soil to grow food, fiber, and ornamental plants. 28 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 29 Exit Slip 1. List 3 factors that are responsible for soil development. 2. What are the four components of soil? 3. How does water move in the soil? 4. What living organisms are found in the soil? 5. How do plants use soil? 30