Week 1 - Topic 1 - Soil Components Flashcards
What is soil?
A complex living ecosystem where living and non-living components interact
From a horticultural perspective, soil is the medium that provides plants with ingredients for growth and support.
What are the 5 main soil components?
- Minerals (Inorganic Material)
- Organic Matter
- Air
- Water
- Organisms
What are the characteristics of minerals in soil?
Derived from weathered parent material (rock), main bulk of soil, break down to provide nutrients to plants
Classified by particle size: Gravel (>2mm), Sand (0.02-2.0mm), Silt (0.002-0.02mm), Clay (<0.002mm).
What is organic matter in soil and what role does it play?
Consists of dead remains of plants and animals, breaks down to form humus, important source of nutrients
Improves drainage in clay soils and enhances water holding capacity in sandy soils.
What role does air play in soil?
Fills spaces between soil particles not occupied by water, essential for plant and animal survival
Roots need oxygen for respiration.
What is the function of water in soil?
Dissolves and transports nutrients, provides moisture for plant growth
Ultimately comes from precipitation.
What types of organisms are found in soil?
Range from microscopic viruses to larger animals, essential for soil development
Include bacteria, fungi, insects, and earthworms.
What are the five key factors in soil formation?
- Parent Material
- Topography
- Climate
- Organisms
- Time
What is the O Horizon in soil?
Organic layer
It is the topmost layer of the soil profile.
What is the A Horizon in the soil profile?
Topsoil
It is generally better for plant growth than subsoils.
What distinguishes soil horizons? (4)
Distinguished by color, texture, pH, and structure.
Each horizon differs in physical, chemical, and biological properties
What are the three main texture classes of soil?
- Sands
- Clays
- Loams
What are the characteristics of sandy soil?
Rapid water infiltration and drainage, poor nutrient retention
High aeration, easy to cultivate, low water holding capacity.
What are the characteristics of clay soil?
Slow air and water movement, high nutrient content
Can become waterlogged, difficult to cultivate, prone to compaction.
What is loam soil considered ideal for?
Ideal for plant growth
Generally consists of ~60% sand, 20% silt, and 20% clay.
What is field texture assessment?
Evaluates grittiness (sand), smoothness (silt), toughness (clay).
Based on feel of moistened soil, quick and requires no special equipment
What is particle size analysis?
Laboratory method for determining soil texture that is more accurate but time-consuming
Not usually necessary for horticultural applications.
True or False: Soil is fragile and can degrade quickly despite taking millennia to form.
True
What is essential for foundation stability in construction?
Soil
Critical for plant growth and ecosystem health.
Fill in the blank: Soil requires careful management to maintain _______.
[fertility]
