Soil Chemistry and Physics Overview

Soil Chemistry

• Studies soil composition, physico-chemical properties, and reactions, including ionic equilibria in submerged soils.
• Analyzes the chemical constitution, properties, and processes occurring within soils.
• Characterizes nutrient reactions in soil and soil solution.

Soil Physics

• Examines physical properties of soils relevant to plant growth and analyzes their measurement.
• Investigates mechanical behavior of soils and physical forces affecting soil properties.
• Focuses on the state and transport of matter (water and energy) in soil.
• Describes soil properties influenced by physical forces mathematically.

Soil Classification and Survey

• Involves studying soil formation, horizon differentiation, and comprehensive classification systems.
• Maps soils and produces soil survey reports, arranging soils into categories based on characteristics.

Soil Geology

• Analyzes common soil-forming rocks, minerals, geological processes, and landforms in relation to agriculture.

Soil Conservation and Management

• Addresses soil deterioration, its control, and maintenance of soil fertility and productivity.
• Protects soil against losses from erosion and chemical degradation through various management practices.
• Encompasses tillage, cropping, fertilization, and other methods to safeguard soil.

Land Use

• Involves the allocation of lands for diverse purposes, including agriculture, housing, and industrial development.

Importance of Soil

• Essential for plant growth, storing water, and supplying nutrients, impacting ecological balance.
• Supports waste recycling and serves as a habitat for microorganisms and an engineering medium.
• Its composition influences water purification and nutrient cycling.

Major Components of Soil

• Consists of mineral matter (45%), organic matter (5%), water (25%), and air (25%), impacting soil properties.
• Solid phase represents about 50% of total soil volume, made up of inorganic and organic materials.

Mineral Matter

• Comprises 45% of soil; includes rock fragments classified as sand, silt, and clay based on particle size.

Organic Matter

• Accounts for 5% of soil volume, consisting of partially decomposed plant and animal material, mainly humus.
• Influences soil properties, increases water retention, and provides essential nutrients for plant growth.

Liquid Phase

• Soil water acts as a solvent, nutrient carrier, and stabilizes soil temperature, essential for plant growth and microbial activity.
• Water availability varies based on precipitation, irrigation, and drainage.

Gaseous Phase

• Soil air is rich in nitrogen (N2) and oxygen (O2), but has higher carbon dioxide (CO2) concentrations than atmospheric air.
• Affects soil respiration and supports aerobic organisms; includes trace gases from microbial metabolism.

Soil Types

• Mineral Soil: Contains less than 20% organic carbon.
• Organic Soil: Contains at least 20% organic carbon.

Quote on Soil

• "Soil is the great connector of lives, the source and destination of all. It is the healer and restorer and resurrector, by which disease passes into health, age into youth, death into life." - Wendell Berry.

Philippine Soils

• A finite resource covering 30 million hectares, vital for agriculture.
• Increasing population leads to conversion of prime agricultural land for urban uses.

Historical Context

• Fertile Crescent marks early agricultural development; agricultural revolutions driven by population growth, shifting cultivation, and practices like the kaingin system.

Areas in Soil Science

• Soil Fertility: Studies nutrient supply, fertilizer usage, and soil amendment.
• Soil Microbiology: Focuses on microbial groups, their ecological roles, and impacts on soil fertility and plant health.
• Edaphology: Examines the influence of soils on living organisms and land use for agriculture.