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Questions and Answers
What is the approximate percentage of pore space in soil?
What is the approximate percentage of pore space in soil?
Which type of soil particle has the greatest capacity for ion exchange?
Which type of soil particle has the greatest capacity for ion exchange?
What is the primary characteristic of loam soil?
What is the primary characteristic of loam soil?
What is the result of having enough sand in soil?
What is the result of having enough sand in soil?
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What is the product of the breakdown of organic matter?
What is the product of the breakdown of organic matter?
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What is the definition of soil texture?
What is the definition of soil texture?
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What is the primary characteristic of clay soils?
What is the primary characteristic of clay soils?
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What is the composition of warm soil?
What is the composition of warm soil?
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What is the primary cause of sediments being lost from the soil?
What is the primary cause of sediments being lost from the soil?
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What type of particles are lost from the soil due to erosion?
What type of particles are lost from the soil due to erosion?
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What is the result of sediments being lost from the soil?
What is the result of sediments being lost from the soil?
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What is the opposite process of erosion?
What is the opposite process of erosion?
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What is the primary factor that contributes to soil erosion?
What is the primary factor that contributes to soil erosion?
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What is the effect of soil erosion on soil fertility?
What is the effect of soil erosion on soil fertility?
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What is the relationship between soil erosion and sedimentation?
What is the relationship between soil erosion and sedimentation?
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What is the consequence of ignoring soil erosion?
What is the consequence of ignoring soil erosion?
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What is the role of vegetation in preventing soil erosion?
What is the role of vegetation in preventing soil erosion?
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What is the impact of soil erosion on the environment?
What is the impact of soil erosion on the environment?
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What is the primary purpose of checking the plasticity of a soil sample?
What is the primary purpose of checking the plasticity of a soil sample?
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What is the purpose of using muslin cloth and rubber bands in the experiment to determine capillarity and infiltration rate?
What is the purpose of using muslin cloth and rubber bands in the experiment to determine capillarity and infiltration rate?
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What is the advantage of adding cress seeds to the experiment to determine capillarity and infiltration rate?
What is the advantage of adding cress seeds to the experiment to determine capillarity and infiltration rate?
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Why is it necessary to dry the soil sample in an oven or microwave in the experiment to calculate the percentage water content?
Why is it necessary to dry the soil sample in an oven or microwave in the experiment to calculate the percentage water content?
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What is the purpose of using a ruler in the experiment to determine capillarity and infiltration rate?
What is the purpose of using a ruler in the experiment to determine capillarity and infiltration rate?
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Why is it necessary to use a clean, dry beaker in the experiment to calculate the percentage water content?
Why is it necessary to use a clean, dry beaker in the experiment to calculate the percentage water content?
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What is the difference between compaction and uncompaction of soil?
What is the difference between compaction and uncompaction of soil?
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What is the purpose of measuring the mass of the soil sample before and after drying in the experiment to calculate the percentage water content?
What is the purpose of measuring the mass of the soil sample before and after drying in the experiment to calculate the percentage water content?
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What is the primary factor that determines the soil texture?
What is the primary factor that determines the soil texture?
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What is the term for the clustering together of soil particles to create larger structures?
What is the term for the clustering together of soil particles to create larger structures?
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What percentage of soil pore space is occupied by air?
What percentage of soil pore space is occupied by air?
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What is the result of soil compaction on soil structure?
What is the result of soil compaction on soil structure?
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What is the consequence of organic matter loss on soil?
What is the consequence of organic matter loss on soil?
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What is the term for the process of soil particles being carried away by wind, destroying soil structure?
What is the term for the process of soil particles being carried away by wind, destroying soil structure?
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What is the result of tillage on soil?
What is the result of tillage on soil?
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What is the purpose of using cover crops?
What is the purpose of using cover crops?
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What is the benefit of good soil structure on plant growth?
What is the benefit of good soil structure on plant growth?
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What is the term for the process of facilitating nutrient retention and exchange in soil?
What is the term for the process of facilitating nutrient retention and exchange in soil?
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What is the primary consequence of sedimentation on topsoil?
What is the primary consequence of sedimentation on topsoil?
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Which type of soil pore is responsible for water retention?
Which type of soil pore is responsible for water retention?
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What is the term for the thin layer of water formed around soil particles due to their polarized nature?
What is the term for the thin layer of water formed around soil particles due to their polarized nature?
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What is the primary reason for the darker color of fertile soils?
What is the primary reason for the darker color of fertile soils?
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What is the effect of lower temperature on seed germination?
What is the effect of lower temperature on seed germination?
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What is the primary purpose of the sedimentation method in soil texture analysis?
What is the primary purpose of the sedimentation method in soil texture analysis?
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What is the term for the removal of carbon dioxide from the atmosphere through plant photosynthesis and storage as organic soil matter?
What is the term for the removal of carbon dioxide from the atmosphere through plant photosynthesis and storage as organic soil matter?
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What is the primary difference between compacted and uncompacted soil in terms of pore space?
What is the primary difference between compacted and uncompacted soil in terms of pore space?
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What is the purpose of the hand testing method in soil texture analysis?
What is the purpose of the hand testing method in soil texture analysis?
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Study Notes
Soil Composition
- Soil is composed of 50% pore space (air and water) and 50% solid matter (mineral and organic matter)
- Mineral matter is derived from parent material, while organic matter is derived from plant and animal remains
Particle Size
- Mineral matter is classified by size: sand, silt, and clay
- Colloidal clay particles are the smallest type of clay particles, but they have the greatest capacity for ion exchange
Soil Types
- Sandy Soils: large air pores, holds water easily, free draining, little leaching, and poor in nutrients
- Clay Soils: poor drainage, leads to waterlogging, and is cold
- Loam Soil: contains equal amounts of sand, silt, and clay, is fertile, easy to work with, and has intermediate characteristics of clay and sandy soils
Soil Texture and Drainage
- Soil texture is a measure of the proportion of different sized particles (sand, silt, clay) in a soil sample
- Soil texture is a fixed property of soil that cannot be changed
- The ratio of Sand, silt, and clay determines the soil texture
Determining Soil Texture
- Hand testing
- Sedimentation
- Soil Sieve
Soil Structure
- Definition: the arrangement of soil particles in a soil
- Key points:
- Floccules are formed by clustering together of soil particles
- Flocculation creates larger structures called floccules or peds
- Arrangement of floccules determines soil pore space (50%: 25% air and 25% water)
- Good structure is necessary for healthy plant growth, nutrient availability, microbial activity, water management, erosion prevention, and resilience to stress
Factors Affecting Soil Structure
- Freezing and thawing
- Wetting and drying
- Compaction: destroys soil structure, reduces pore space, increases soil density, and reduces infiltration and drainage
- Organic Matter Loss: leads to poorer structure, less nutrient availability, and lower water retention
- Erosion, Sedimentation, and Weathering: can be broken into three areas – wind, water, and tillage, and can be reduced by using cover crops, crop rotation, and reducing compaction### Soil Erosion and Sedimentation
- Erosion leads to loss of topsoil, which is crucial for fertility, nutrients, cation exchange, and trapping carbon.
- Sedimentation is the process of transporting and depositing eroded soil particles to a new location, potentially affecting water quality.
- Sediments can carry excess nutrients (manure) and pathogens.
Soil Structure and Water
- Large soil pores facilitate drainage, while small soil pores enable water retention for plant uptake.
- Clay soils have small pores, making them prone to waterlogging.
- Loam soil is ideal, with a balance of large and small pores.
- Water is attracted to the negative charges of clay particles, forming a thin layer around them (hygroscopic water).
- Capillary water and gravitational water are two types of water in soil.
Soil Colour and Properties
- Dark brown or black soil colours indicate rich, fertile soils with high humus content.
- Light or grey soil colours suggest low fertility, low nutrients, and leaching.
- Red soil colours indicate the presence of iron, which can form an impermeable iron-pan.
Soil Temperature
- Lower temperatures result in lower germination rates and water and mineral uptake.
- Van't Hoff's Law states that the rate of chemical reactions doubles with every 10°C rise in temperature.
Soil Compaction and Pore Space
- Compaction affects soil structure, impacting temperature, water, and mineral uptake.
- An experiment can be conducted to compare the total pore space in compacted and uncompacted soil.
Soil Texture Analysis
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Sedimentation, soil sieving, and hand testing are methods to investigate soil texture.
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The sedimentation method involves adding soil to a beaker, stirring, and pouring the mixture into a graduated cylinder to settle.### Soil Texture Analysis
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Observe layers in a soil sample: clay at the top, silt in the middle, and sand at the bottom
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Record levels of each layer using a graduated cylinder
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Calculate the percentage of sand, silt, and clay in the sample
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Use the soil triangle to classify the soil type
Soil Sieve Method
- Dry the soil sample in an oven to remove moisture
- Crush the sample using a pestle and mortar
- Weigh the empty weighing boat, then add the crushed sample and reweigh
- Subtract the mass of the empty boat to calculate the mass of the soil
- Place the crushed sample in a series of sieves with decreasing mesh sizes
- Shake the sieves and weigh the contents of each to calculate the percentage of sand, silt, and clay
- Use the soil triangle to classify the soil type
Hand Testing Method
- Take a dry soil sample and rub it between your thumb and fingers to note its grittiness/smoothness
- Wet the sample and rub it again to note its grittiness/smoothness and plasticity (ability to be moulded)
- Use a flow chart to identify the texture of the soil sample based on its grittiness, smoothness, and plasticity
- Attempt to roll the wet sample into threads and make a ring to further identify the texture
Capillarity and Infiltration Rate
- Compare the capillarity and infiltration rate of compacted and uncompacted soil using two open-ended glass tubes
- Cover one end of each tube with muslin cloth and fill with soil
- Stand both tubes in a water trough and observe the rise in water level over time
- Measure the level of water risen using a ruler
- Compare the results of both soils
Percentage Water Content
- Calculate the percentage water content in a soil sample using a beaker, weighing scales, and a microwave or oven
- Find the mass of a clean, dry beaker, then add a moist soil sample and find the mass of the beaker and soil
- Dry the soil in the oven at 105°C until all water has evaporated, then calculate the loss in mass
- Repeat for multiple soil samples (e.g., sandy, clay, loam)
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Description
This quiz covers the physical features of soil, including its composition and particle size. Learn about the proportion of pore space, mineral matter, and organic matter in soil.
