3.2.5 Soils Flashcards
What is soil
The top layer of earh’s surface, made off of weathered rock, organic matter, air, and living organisms
What is soil vital for
Effective growth of plants, which are the ‘starters’ of food chains & ecosystems
What is a fertile soil
A soul that has the nutrients to sustain plant growth
State the 9 features of a fertile soil
Ability to hold water
Nutrients and minerals
Good air content
Relatively neutral pH
DOM (dead organic matter)
Soil depth
High levels of soil biota
Soil structure
Soil texture
Why is water important for fertile soil?
Water is needed for plant survival, photosynthesis, and nutrient absorption.
What happens if soil becomes waterlogged?
It prevents air from reaching plants and organisms, which can harm soil fertility.
What nutrients are found in fertile soil?
Macronutrients (e.g., nitrogen, potassium, phosphorus) and micronutrients (e.g., copper, iron, magnesium).
How do plants absorb macronutrients?
Through the absorption of dissolved nutrients in water.
Why are heavy metals in soil dangerous?
They are not absorbed by plants and can dissolve in water, harming plant and animal life.
Why is good air content important in soil?
It allows oxygen to reach plants and animals and helps decomposition break down waste.
How does aeration affect soil fertility?
Aerated soils are usually more fertile because decomposition requires oxygen.
What is the ideal pH range for fertile soil?
5.5-7.0
What happens if soil is too acidic or too alkaline?
Acidic soil damages plant membranes and leaches nutrients; alkaline soil makes macronutrients insoluble.
What is DOM (dead organic matter)
Decomposed plant and animal material that releases nutrients into the soil.
How does DOM improve soil fertility?
It increases macronutrients and helps the soil retain water.
What is the importance of soil depth in soil fertility?
Deeper soils hold water for longer, dry out less rapidly, and don’t become waterlogged easily. They provide stability and ensure plants have enough root space for growth.
What is soil biota, and why is it important?
Soil biota refers to the living organisms in soil that process organic matter (DOM) into nutrients, improving fertility.
What is the role of mycorrhizal fungi in soil fertility?
Mycorrhizal fungi form a symbiotic relationship with plant roots, aiding in phosphate absorption.
What do decomposers do in the soil?
Decomposers, including fungi and bacteria, release enzymes to digest DOM. They rely on detritivores to break down DOM into smaller pieces first.
What are detritivores, and how do they benefit soil fertility?
Detritivores (e.g., worms, millipedes, slugs) break down large DOM into smaller pieces, releasing nutrients. They also create tunnels and burrows, improving soil aeration.
What role do bacteria (nitrogen fixers) play in soil fertility?
Nitrogen-fixing bacteria convert gaseous nitrogen into ammonium ions, making it usable for plants.
What do nitrifying bacteria do in soil?
Nitrifying bacteria oxidize ammonium ions (from animal waste) into nitrite ions and then nitrate ions, which are essential for plant growth.
What is soil texture
Characteristics of a soil based on the proportion of the mineral particles that are sand, silt and clay
Depends on the properties of the mineral particles
Can have a large influence on a variety of factors
Give the steps of the soil texture practical
1) soil into container- measure the ml (total volume)
2) add water- volume must be same for each soil samples
3) agitate/invert for 2 mins
4) 2 mins later record ml of soil settled = sand
5) 2 hrs = silt
6) 2 days = clay
