Presentation on theme: "Formation and Characteristics of Hawaii’s Soils. What is Soil? Soil is formed from the weathering of rocks and minerals (pedogenesis). Serves as a natural."— Presentation transcript:
Formation and Characteristics of Hawaii’s Soils
What is Soil? Soil is formed from the weathering of rocks and minerals (pedogenesis). Serves as a natural medium for the growth of land plants. Decaying matter from plant and animals makes the soil thick and rich. Shows effects of living and environmental factors.
The Importance of Soil Sustain plant and animal life both above and below the surface Regulate water and solute flow. Store and cycle nutrients. Provide support for buildings and structures
Soil Composition Soil generally consists of organic and inorganic materials, water and air. The inorganic materials are the rocks that have been broken down into smaller pieces. The organic material is decaying living matter (plants or animals). The amount of water and air in the soil is closely linked with the climate and other characteristics of the region.
Soil Forming Factors 1.Parental Material: The primary material from which the soil is formed. 2.Climate: weathering forces break down parent material. 3.Organisms: All plants and animals living in or on the soil. 4.Topography: The location of a soil on a landscape can affect how the climatic processes impact it. 5.Time: All of the above factors assert themselves over time
Weathering Weathering is the physical breaking-down and chemical alteration of the soil. Physical weathering is the disintegration of rock without changing its chemical composition. Chemical weathering is the decomposition of soil particles by chemical alteration.
Describing Soil Particle size –Small particles have increased surface area such as clays retain water. –Large particles provide better drainage, retain very few nutrients. Soil texture: is the relative proportion of silt, clay, and sand in the soil. –Clay: smaller than.002 mm –Silt: to 0.05 mm –Sand: up to 2.0 mm Soil permeability: how fast water can move downward in a particular soil
Sand, Silt and Clay Sand and silt are the product of physical weathering Clay is the product of chemical weathering. Clay content has a higher retention of nutrients and water. Clay soils resist wind and water erosion better than silty and sandy soils
Soil Profile Soil Horizons: the various layers in the soil. Soil Profile: The arrangement of these horizons Soil horizons differ in a soil properties such as color, texture, structure, and thickness Soil horizons also differ in their chemical and mineral content the surface horizon (A), the subsoil (B), and the substratum (C). Some soils have an organic horizon (O)
Movement of Materials in Soil Eluviation: the movement of material from one place to another within the soil. Illuviation: the collection of material that has been eluviated.
Leaching and Pesticides Leaching: the movement of a chemical (natural or synthetic) with water moving downward through soil or rock. Pesticides and other contaminants can leach into groundwater. Pesticide Factors –Solubility: some pesticides dissolve easily in water and are more likely to move into water systems. –Adsorbtion: some pesticides become tightly attached (strongly adsorbed) to all soil particles and are not likely to move out of the soil and into water systems. –Persistence: some pesticides evaporate or break down slowly and remain in the environment for a long time.
Soil Chemistry (pH) Soil pH is a measure of the acidity or alkalinity in the soil. Soil pH influences the solubility of nutrients. Soil pH affects the activity of micro-organisms. Most plants enjoy a slightly acidic (pH 6-7) environment.
Soil Chemistry (Organic Material) Organic matter… Enhances water and nutrient holding capacity Improves soil structure Enhance productivity and environmental quality Reduce atmospheric CO 2 levels that contribute to climate change.
Soil Erosion Erosion is the displacement of soil and rock by ocean currents, wind, water, or ice. A certain amount of erosion is natural and, in fact, healthy for the ecosystem. Erosion Factors –Precipitation –Soil composition –Slope Gradient –Vegetation –Land use
Crop Rotation Crop rotation is the practice of growing of different types of crops in the same space in sequential seasons It avoids the buildup of pathogens and pests It seeks to balance the fertility demands of various crops to avoid excessive depletion of soil nutrients.
Fertilizers Fertilizers contain nutrients that improve the quality and quantity of plant growth. Excessive use of fertilizers can lead to nutrient pollution.
Hawaiian Soil Profile (Ultisol) Consists of very deep, moderately well drained soils. Formed in many layers of volcanic ash, igneous rock with lesser amounts of dust from the deserts of central Asia. Slight acidic top layer and strongly acidic sub layer Some areas very strongly acidic
Aquifers Aquifer: a geologic body which is porous and permeable enough to become saturated with water and yields water when wells are drilled into it. Recharge: is water that soaks into the ground and adds to aquifers. Rainwater is the main source of recharge in Hawaii.