Soil Formation and Geography

• Geography examines Earth's physical features, atmosphere, and human activities.
• It studies the interaction of human culture with the natural environment along with their spatial relationships.
• Soil resources are important to agriculture, forestry, and overall ecosystem health.
• Soil consists of a mix of minerals, organic matter, water, and air.

Soil Formation

• Soil formation, also known as pedogenesis, is the process of rocks breaking down and transforming into soil.
• Weathering is key and involves the breakdown of rocks and minerals.
• Physical weathering includes mechanical disintegration like freeze-thaw cycles.
• Chemical weathering includes reactions like oxidation and hydrolysis.
• Biological activity, such as plant roots and microorganisms, helps break down parent material.
• Parent material is the underlying geological material from which soil originates, which affects soil texture and composition.
• Climate (temperature and precipitation) impacts the rate and type of weathering.
• Topography affects soil drainage and erosion patterns.
• Living organisms (biota) support organic matter accumulation and nutrient cycling.
• Time is a key factor, as soil development is a gradual, ongoing process.

Soil Composition

• Mineral particles include sand, silt, and clay which define soil texture.
• Organic matter comprises decomposed plant and animal residues that improve soil structure, water retention, and nutrient availability.
• Water is vital for plant growth and nutrient transport.
• Air provides oxygen for root respiration and microbial activity.
• Soil organisms, like bacteria, fungi, earthworms, and insects, are important in decomposition, nutrient cycling, and soil structure.

Soil Properties

• Soil texture is the proportion of sand, silt, and clay, affecting water-holding capacity, drainage, and aeration.
• Sandy soils have quick drainage, low water-holding capacity, and are easy to till.
• Clay soils drain slowly, have high water-holding capacity, and are hard to till.
• Loam soils are a balanced mix of sand, silt, and clay, offering great conditions for plant growth.
• Soil structure is how soil particles arrange into aggregates or peds, influencing aeration, drainage, and root penetration.
• Granular structure (small, rounded aggregates) is best for plant growth.
• Platy structure (flat, layered aggregates) restricts water and air movement.
• Soil porosity is the amount of pore space in the soil, which impacts aeration, drainage, and water-holding capacity.
• Macropores (large pores) help drainage and aeration.
• Micropores (small pores) hold water.
• Soil color can show the composition and properties of soil.
• Dark soils have lots of organic matter.
• Red soils indicate the presence of iron oxides.
• Soil pH measures acidity or alkalinity, affecting nutrient availability and microbial activity.
• Most plants thrive in slightly acidic to neutral soils (pH 6-7).
• Soil fertility is the soil's ability to supply essential nutrients for plant growth.
• Macronutrients (N, P, K, Ca, Mg, S) are needed in large quantities.
• Micronutrients (Fe, Mn, Zn, Cu, B, Mo, Cl) are needed in small quantities.

Soil Types

• Soil taxonomy is a system of classifying soils based on properties and characteristics.
• Soil orders are the broadest classification level, based on soil-forming processes.
• Alfisols are moderately weathered with high base saturation, common to humid and subhumid regions.
• Andisols are volcanic with high water-holding capacity and fertility.
• Aridisols are desert soils that have low organic matter and limited water.
• Entisols are young soils that are undeveloped and have minimal horizon development.
• Gelisols are permafrost-affected and are in cold regions.
• Histosols are organic-rich soils found in wetlands and bogs.
• Inceptisols are weakly developed which means they have some horizon development.
• Mollisols are grassland soils, they have a thick, dark surface that is rich in organic matter.
• Oxisols are highly weathered and are found in tropical regions, they have low fertility but high iron and aluminum.
• Spodosols are acidic with a distinct spodic horizon and can be found in coniferous forests.
• Ultisols are highly weathered with low base saturation, common in warm, humid regions.
• Vertisols are clay-rich which means they swell and shrink with changes in moisture.

Soil Degradation

• Soil erosion is when soil is detached and transported by wind or water.
• Water erosion includes sheet, rill, and gully erosion.
• Wind erosion is common in dry regions.
• Soil compaction reduces pore space, restricting root growth, water infiltration, and aeration.
• Chemical degradation includes nutrient depletion, salinization, and acidification.
• Nutrient depletion happens when nutrients are removed faster than they are replaced.
• Salinization is salt accumulation, often from irrigation in dry regions.
• Acidification is a drop in soil pH, often from acid rain or too much fertilizer.
• Soil pollution is when harmful substances contaminate the soil.
• Industrial waste, pesticides, and heavy metals can pollute soil.

Soil Conservation

• Conservation tillage reduces soil disturbance, which lowers erosion while improving soil structure.
• Contour plowing is plowing along land contours, reducing water erosion.
• Terracing creates level platforms on slopes, reducing water erosion.
• Cover cropping uses crops to protect soil from erosion and improve fertility.
• Crop rotation alternates crops to improve soil health and reduce pest and disease issues.
• Windbreaks are rows of trees or shrubs that reduce wind erosion.
• Integrated nutrient management uses organic and inorganic fertilizers to maintain soil fertility.
• Phytoremediation uses plants to remove pollutants.

Soil and Land Use

• Agriculture uses soil for crop production and livestock grazing.
• Forestry depends on soil for tree growth and timber.
• Urban development converts soil for housing, roads, and infrastructure.
• Mining can disturb and pollute soil.
• Recreation, for parks and golf courses, also uses soil.

Importance of Soil

• Soil is key to food production because it acts as the medium for plant growth and nutrient supply.
• It helps with water filtration and purification by removing pollution.
• Soil supports biodiversity and acts as habitat for organisms.
• It helps regulate climate by carbon sequestration and managing greenhouse gas emissions.
• Soil is a building material used for construction.

Explore soil formation, a key aspect of physical geography. Learn about weathering processes, including physical and chemical mechanisms. Understand the influence of parent material and biological activity on soil composition and its importance.