Soils PP.ppt.pdf

Soil Management Terms See your first pages in handout Why soils are important Plants grow in and on soil Plants support animal life Plants and animals support human life World population is rapidly increasing and/or has inadequate nutrition Supply of productive soils in limited Improved soil managem...

Soil Management Terms See your first pages in handout Why soils are important Plants grow in and on soil Plants support animal life Plants and animals support human life World population is rapidly increasing and/or has inadequate nutrition Supply of productive soils in limited Improved soil management could feed more people How is soil related to plants Media for seed germination Media for support of plants Storehouse of plant nutrients Storehouse of water for the plant Soil – the top layer of the. Earth’s crust, which is suitable for the growth of plant life Leached – certain elements have been washed out of the soil. Parent Material – the horizon of unconsolidated material from which soil develops. Horizon - layer Profile – a cross sectional view of soil. Residual Soil – parent material formed in place. Alluvial Deposit – soils transported by streams. Colluvial Deposit – soils deposited by gravity. Permeable - permitting movement. Capability Class – soil classification indicating the most intensive but safe land use. Capability Subclass – soil group within a class designated by a small letter. Capability Unit – soil group within a subclass. Clay – smallest of soil particles; less than 0.002mm. Silt – intermediate soil particles; 0.05-0.002 mm. Sand – largest soil particle; 1 to 0.05mm. Topsoil – desirable proportion of plant nutrients, chemicals, and living organisms located near the surface that supports good plant growth. Subsoil – a soil layer that corresponds to the b-horizon that is composed almost entirely of mineral with generally large chunky soil structure. Bedrock – the area below horizon C consisting of large soil particles.Also the place Fred Flintstone lived. SOILS MANAGEMENT What factors affect soil formation? 1. Structure of original parent material A. Residual Igneous – molten materials (granitic) Metamorphic – pre-existing rocks combined with heat and pressure (quartzite) Sedimentary-sediments deposited by wind, water or ice (limestone) What factors affect soil formation? B. Transported Wind (loess) Water (alluvial) Glaciers (glacial drift) Gravity (colluvial) What factors affect soil formation? 2. Decomposition by weathering A. Physical Weathering Wind Plants and animals Heating and cooling- Increase temperature = Increase chemical reactions and Increase in growth of microorganisms and plants Freezing and thawing Wetting and drying rainfall What factors affect soil formation? B. Chemical Weathering Rxn’s of water, O2 and CO2 B. Chemical Weathering C. Biological Weathering Micro-organisms help decompose rocks What factors affect soil formation? 3. Cover of vegetation and organisms A. Plant (linches, mosses, grasses, etc.) B. Animal (bacteria, fungi, mammals, birds, man) What factors affect soil formation? 4. Slope and Drainage A. Hillsides Thin top soils erode easily Reduced plant growth Lower organic matter Less leaching What factors affect soil formation? B. Flat Lands Deeper topsoil More veg. High organic matter Greater leaching Percolation – water soaks in and moves through soil the Permeable – permits water movement Wet soil = little or no air = reduced microorganism soil. action = slower forming Composition of Soil A. Solids (50%) Mineral matter -45% Organic Matter & living organisms-5% B. Pore Space (50%) Water (25%) Air (25%) Composition of Soil Benefits of Organic Matter Makes soil porous Supplies nitrogen and other nutrients to plants Holds water in the soil Furnishes food for soil organisms SOIL TEXURE & STRUCTURE Coarse-textured (sandy) soil — loose and single-grained soil. Medium-textured (loamy) soil — a relatively even mixture of sand, silt, and clay. Fine-textured (clay) soil — usually forms very hard lumps or clods when dry; plastic when wet. Structure — refers to the tendency of soil particles to cluster together and function as soil units. Aggregates — soil units containing mostly clay, silt, and sand particles held together by a gel-type substance formed by organic matter. Crumbs — aggregates. SOIL PARTICLES Mineral matter — nonliving items such as rocks. Clay — smallest of soil particles; less than.002 mm. Silt — intermediate soil particles;.05 to.002 mm. Sand — largest soil particles; 1 to.05 mm. TYPES OF SOILS Residual soils parent material formed in place. Alluvial deposits soils transported by streams. Lacustrine deposits soils deposited by lakes. TYPES OF SOILS Loess deposits soils deposited by wind. Colluvial deposits soils deposited by gravity. Glacial deposits soils deposited by ice. SOIL HORIZONS Horizon — layer. O horizon — the soil layer that is on the surface that is composed of organic matter and a small amount of mineral matter. A horizon — soil located near the surface that is made up of desirable proportions of mineral and organic matter. B horizon — soil below the A horizon or topsoil and generally referred to as subsoil. C horizon — soil below the B horizon; it is important for storing and releasing water to the upper layers of soil. Bedrock — the area below C horizon consisting of large soil particles. Subsoil — a soil layer that corresponds to the B horizon that is almost entirely composed of mineral matter with generally large chunky soil structure. Topsoil — desirable proportion of plant nutrients, chemicals, and living organisms located near the surface which support good plant growth. Characteristics of deep & Shallow soils Deep Unrestricted plant growth Increases potential plant growth Less susceptibility to lodging Higher yields Easier to cultivate Wide variety of crop uses Shallow Restricted root growth Potential plant growth is restricted Increases chance of lodging Lower yields Hard to cultivate Limited crop use Ways Erosion limits productivity Lower tillable acres Sediment in streams may cause flooding or raise the water table Removes productive layer of soil. Hard to prepare land and harvest Low organic matter Displaces nutrients Higher cost of production b/c of management practices Acidity or Alkalinity and pH Determined by the # of hydrogen (H+) ions, and hydroxyl (OH-) ions More H+ ions than OH- ions the soil will be more acid More OH- ions than H+ ions the soil will be more alkaline A neutral soil has equal amounts of H+ and OH- ions Expressed in pH values from 1-14 Best plant growth from 6-7.5 pH Poor growth < 5.2 and > 8.3 Acidity or Alkalinity and pH Low pH is more common than high pH Add Lime to raise pH 3 tons of lime can raise the soil pH one number on the scale Liming soils Correct acidity of soil by adding lime Lime neutralizes the H+ ions Amount of lime depends on: Degree of acidity Crops to be grown Grade and purity of lime Frequency of application Soil texture Types of Alkaline soils Saline ( accumulation of soluble salts – NaCL (table salt) Sodic ( acuumulation of sodium (Na) Saline-Sodic (both salt and sodic affect) See notes in outline Most crops do not grow well on soils that contain salts. One reason is that salt causes a reduction in the rate and amount of water that the plant roots can take up from the soil. Also, some salts are toxic to plants when present in high concentration. Reclamation of Alkali soils Saline Flood with water and leach out salts Install drainage tiles Grow salt tolerant crops (barely, sugar beets, cotton) Sodic Apply gypsum (which is rich in calcium and Grow sodic tolerant crops (rice, sugarbeets) Saline – sodic Correct sodic then salt problem LAND CAPABILITY Capability classes — soil classifications indicating the most intensive, but safe land use, designated by a Roman numeral. Capability subclasses — soil groups within a class designated by a small letter. Capability unit — soil group with a subclass. CAPABILITY CLASSES – Suitable for Cultivation Class I – Soils have few limitations that restrict their use. Requires good soil management practices only Class II – Soils have moderate limitations that reduce the choice of plants or require moderate conservation practices. Moderate conservation practices necessary CAPABILITY CLASSES – Suitable for Cultivation Class III - Soils have severe limitations that reduce the choice of plants, require special conservation practices, or both. Intensive conservation practices necessary Class IV – Soils have very severe limitations that reduce the choice of plants, require very careful management, or both. Perennial vegetation, infrequent cultivation CAPABILITY CLASSES – No Cultivation, Hay, and Woodland Class V – Soils are not likely to erode, but have other limitations, impractical to remove, that limit their use. No restrictions in use Class VI – Soils have severe limitations that make them generally unsuitable for cultivation. Moderate restrictions in use CAPABILITY CLASSES – No Cultivation, Hay, and Woodland Class VII – Soils have very severe limitations that make them unsuitable for cultivation. Severe restrictions in use Class VIII – Soils and landforms have limitations that nearly prevent their use for commercial plants. Best suited for wildlife and recreation CAPABILITY SUBCLASSES e – Erosion Main limitation is risk of erosion unless close-growing plant cover is maintained w – Excess water Water in or on the soil interferes with plant growth or cultivation s – Shallow, droughty or stony soil Limited because it is shallow, droughty or stony c – Climate too cold or too dry Indicates chief limitation is climate Used only in some parts of the United States