Understanding Soil: Composition, Parent Materials, and Properties, Slides of Botany and Agronomy

Download Understanding Soil: Composition, Parent Materials, and Properties and more Slides Botany and Agronomy in PDF only on Docsity! Soil Characteristics Docsity.com Soil • a layer of natural materials on the earth’s surface containing both organic and inorganic materials and capable of supporting plant life. Docsity.com Soil • Ideal soil should contain about 50% solid material and 50% pore space. • About half of the pore space should contain water and half of the space should contain air. Docsity.com Soil • Inorganic material consists of rock slowly broken down into small particles. • The organic material is made up of dead plants and animals varying in stages of decay. Docsity.com Soil • The percentages of the four main soil components varies depending on the kind of vegetation, amount of mechanical compaction, and the amount of soil water present. Docsity.com Parent Material • Minerals are solid, inorganic, chemically uniform substance occurring naturally in the earth. • Some common minerals for soil formation are feldspar, micas, silica, iron oxides, and calcium carbonates. Docsity.com Parent Material • Rocks are different from minerals because they are not uniform. • There are three types of rocks, igneous, sedimentary, and metamorphic. Docsity.com Parent Material • Igneous rocks are those formed by the cooling of molten rock. • Sedimentary rocks are those formed by the solidification of sediment. Docsity.com Parent Material • Loess deposits are generally thought of as windblown silt. • Alluvial and marine deposits are water borne sediments. • Alluvial deposits are left by moving fresh water. • Marine deposits are formed on ancient ocean floors. Docsity.com Parent Material • Organic deposits are partially decayed plants that live plants are able to root and grow in. • These are found in swamps and marshes. Docsity.com Weathering • When minerals are exposed to weather, they begin to break down into smaller pieces. • This is mostly done by heating and cooling of the minerals and rock. Docsity.com Weathering • Ice can also speed up the weathering process on rocks. • If a rock has a crack that can fill up with water, when the water freezes, it can literally crumble the rock into small pieces. Docsity.com Weathering • Rocks can also be broken down by mechanical grinding such as wind blowing sand at high speeds or glaciers causing rocks to grind each other. Docsity.com Weathering • New soil is continually being made, but it takes a long time to create new soil and if it isn’t managed properly, soil can be eroded away quicker than it can be made. Docsity.com Organic Matter • There are two types of organic matter. • Original tissue is that portion of the organic matter that can still be recognized. • Twigs and leaves covering a forest floor are good examples. Docsity.com Organic Matter • Humus is organic matter that is decomposed to the point where it is unrecognizable. • The brown color you sometimes see in soil is a good example. Docsity.com Organic Matter • Purposes of organic matter: affects the soil structure by serving as a cementing agent, returns plant nutrients to soil (P, S, N), helps store soil moisture, makes soil more tillable for farming, provides food (energy) for soil microorganisms, which makes the soil capable of plant production Docsity.com Soil Physical Properties • Slope is defined as the angle of the soil surface from horizontal. • It is expressed as the % of rise over run. Docsity.com Soil Physical Properties • Slope effects the productive potential in numerous ways: Rain runoff, soil erosion, the use of farm machinery, and contour farming. Docsity.com Soil Physical Properties • Texture refers to the proportions of sand silt and clay in the soil. • Course-textured soils are and sandy and do not hold water well, while fine-textured soils contain clay and tend to hold more surface moisture. Docsity.com Soil Physical Properties • A field used for crop production that has little or no erosion can continue to be used for crops. • But a severely eroded field may need to be turned into pasture where it is always covered. Docsity.com Soil Physical Properties • Topsoil and subsoil thickness refer to the depth of those layers that are available for plant production. • Thin topsoil and/or thin subsoil can greatly limit crop production Docsity.com Land Capability Classification • Land capability class categorize the productive potential of the soil. • The classes generally range from class 1, the best land for agricultural production, to class VIII, the least productive. Docsity.com Land Capability • Class II is just as good, but it may have some limitations such as sloping land or slight erosion. Docsity.com Land Capability • Class III can still be cultivated, but it has some severe limitations. • The land may have moderate slope, erosion or a shallow root zone. Docsity.com Land Capability • Class IV has severe limitations, but can still be cultivated with good management practices. Docsity.com Land Capability • Class VII has some severe limiting properties. • It may be very steep or be severely eroded and have deep gullies Docsity.com Land Capability • Class VII may be very course. • This can be turned into pasture but grazing must be controlled. • It can also be used as forest or recreation. Docsity.com Land Capability • Class VIII has one or more extreme limitations. • It should be left in its natural state for recreation and wild life. • It has little agriculture value. Docsity.com