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Questions and Answers
What characterizes horizon A in the soil profile?
What characterizes horizon A in the soil profile?
- It has a mix of clay and rock fragments.
- It allows easy root penetration. (correct)
- It is rich in soluble salts.
- It consists mostly of large particles.
What is the primary composition of horizon C?
What is the primary composition of horizon C?
- Completely disintegrated material.
- Mixture of large and small particles. (correct)
- Unweathered parent rock.
- Highly organic soil with rich nutrients.
Which statement is true about horizon B?
Which statement is true about horizon B?
- Root penetration is easy due to its structure.
- It is found above horizon A in the soil profile.
- It contains mostly small particles and soluble salts. (correct)
- It has the highest concentration of organic matter.
How does horizon D differ from the other horizons in the soil profile?
How does horizon D differ from the other horizons in the soil profile?
Which characteristic is true for the zone of concentration (horizon B)?
Which characteristic is true for the zone of concentration (horizon B)?
What characterizes sandy soil compared to heavy soil?
What characterizes sandy soil compared to heavy soil?
Which soil type has the fastest rate of water movement?
Which soil type has the fastest rate of water movement?
What is the primary component of horizon A in the soil profile?
What is the primary component of horizon A in the soil profile?
How does rainfall affect the soil profile?
How does rainfall affect the soil profile?
What is the expected infiltration time of water in sandy soil?
What is the expected infiltration time of water in sandy soil?
What role do microorganisms play in sandy soil?
What role do microorganisms play in sandy soil?
Which layer is described as having a poor concentration of soluble substances?
Which layer is described as having a poor concentration of soluble substances?
What is a significant characteristic of loamy soil?
What is a significant characteristic of loamy soil?
What type of soil is defined when the weight of gravels and sand exceeds the weight of silt and clay?
What type of soil is defined when the weight of gravels and sand exceeds the weight of silt and clay?
During the sieve method, what is the first step in the process?
During the sieve method, what is the first step in the process?
Which soil type is characterized by having most particles as large and a low ratio of small particles?
Which soil type is characterized by having most particles as large and a low ratio of small particles?
What is the diameter range for medium sand according to soil particle classification?
What is the diameter range for medium sand according to soil particle classification?
In soil analysis, which group is considered to have colloidal properties?
In soil analysis, which group is considered to have colloidal properties?
What is the smallest particle size category for soil according to the classification given?
What is the smallest particle size category for soil according to the classification given?
What separation outcome indicates a soil is classified as loamy?
What separation outcome indicates a soil is classified as loamy?
In the sieve method, the soil particles are classified into groups based on what criteria?
In the sieve method, the soil particles are classified into groups based on what criteria?
Which soil texture has the highest water holding capacity?
Which soil texture has the highest water holding capacity?
What effect does high fine particle content have on soil fertility?
What effect does high fine particle content have on soil fertility?
Which type of soil allows for the quickest water infiltration?
Which type of soil allows for the quickest water infiltration?
How does the mechanical resistance of heavy soil affect root penetration?
How does the mechanical resistance of heavy soil affect root penetration?
What role do colloidal properties of fine particles play in soil?
What role do colloidal properties of fine particles play in soil?
Which type of soil is least resistant to aeration?
Which type of soil is least resistant to aeration?
What happens to water in sandy soil due to its particle size?
What happens to water in sandy soil due to its particle size?
How does soil texture affect runoff during rainfall?
How does soil texture affect runoff during rainfall?
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Study Notes
Soil Texture and Mechanical Analysis
- Soil texture is determined by the size of soil particles.
- Soil particle size is measured using mechanical analysis, with the sieve method being a common technique.
- The sieve method involves shaking a set of sieves with soil for an hour.
- The weight of soil particles retained in each sieve determines the percentages of gravel, sand, silt, and clay.
Soil Particle Size Classifications
- Coarse gravel: > 2.00 mm
- Fine gravel: 2.00 - 1.00 mm
- Coarse sand: 1.00 - 0.50 mm
- Medium sand: 0.50 - 0.25 mm
- Fine sand: 0.25 - 0.10 mm
- Very fine sand: 0.10 - 0.05 mm
- Silt: 0.05 - 0.002 mm
- Clay: < 0.002 mm
Soil Types Based on Texture
- Sandy soil: Predominantly large particles (gravel and sand), resulting in large pore spaces.
- Loamy soil: A balanced mix of large and small particles.
- Clay soil/Mud: Predominantly small particles (silt and clay), leading to small pore spaces.
Characteristics of Soil Particles
- Large particles (gravel and sand): No colloidal properties, not active in water or nutrient absorption.
- Small particles (silt and clay): Have colloidal properties, actively absorb water and soluble nutrients.
Effects of Soil Texture on Soil Properties
Water Holding Capacity
- Sandy soil: Low water holding capacity due to larger pore spaces and lack of colloidal properties.
- Clay soil: High water holding capacity due to smaller pore spaces and colloidal properties.
- Loamy soil: Intermediate water holding capacity.
Water Infiltration
- Sandy soil: Rapid and easy water infiltration.
- Clay soil: Slow and difficult water infiltration, leading to runoff and surface evaporation.
- Loamy soil: Intermediate water infiltration.
Fertility
- Clay soils: Higher fertility due to the adsorption of nutrients on the surfaces of fine particles.
- Sandy soils: Lower fertility due to limited nutrient retention.
Mechanical Resistance to Root Penetration
- Clay soils: High resistance due to smaller pore spaces and compacted structure.
- Sandy soils: Low resistance, allowing for longer and more extensive root systems.
Soil Aeration
- Sandy soils: Good aeration due to large pore spaces.
- Clay soils: Poor aeration due to small pore spaces.
Water Movement in Soil
- Sandy soils: Fastest rate of water movement.
- Clay soils: Slowest rate of water movement.
Soil Profile
- Soil profile is a vertical section of soil showcasing different layers called horizons.
- Horizons are differentiated by particle size, chemical structure, and solubility.
- Horizon A (Zone of Extraction): Upper layer with larger particles, poor in soluble salts, and easy root penetration.
- ** Horizon B (Zone of Concentration):** Layer below Horizon A, enriched in fine particles and soluble salts. Roots have difficulty penetrating due to compaction.
- Horizon C (Zone of Weathered Parent Material): Parent rock material broken down by weathering.
- Horizon D (Bedrock Zone): Original, unweathered rock.
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