1. Components of a fertile soil

2. What makes up a fertile soil?
A fertile soil is one that will maintain life, and is made up of minerals, organic matter, water, air and living organisms.

3. Mineral Components Sand
Formed by physical weathering
Feels gritty
Does not hold together
Easy to cultivate
Called ‘light soils’
Have large spaces between the grains (pores) so water moves through quickly
Dry out quickly
Warm up quickly in spring
Need irrigation in warm dry weather

4. Advantages and Disadvantages of Sandy Soils
Warm up earlier
Less damaged by compaction
Less expensive to cultivate
Disadvantages
Dry out quickly
Low water storage capacity so crops growing on them suffer droughts
Too well aerated, this tends to destroy organic matter
Tends to be more leached (nutrients leave the soil with the movement of water)

5. Clay Formed by chemical weathering
Particles stick together so they feel sticky
‘heavy’ to work
Swell when wet and shrink when dry
Absorb water easily
Slow to warm in spring
Clays hold some elements essential to plant growth e.g. calcium, magnesium, potassium and sodium.
Particles clump together or FLOCCULATE in the presence of lime – this provides larger spaces for the water to drain through.

6. Advantages and Disadvantages of Clay soils
Good water holding capacity
Rich in plant nutrients
Disadvantages
Water does not drain through readily
Slow to warm up in spring
Puddle when wet and set like concrete when dry
Expensive to cultivate
In high rainfall areas may develop an iron pan or a clay pan which leads to water logging
Susceptible to damage from stock and implements especially when very wet or very dry

7. Silt Consists of particles in size between sand and clay
Has a slippery or silky feel
Pure silt soils erode easily as they do not have good structure
Have properties between sandy and clay soils
Silt soils have the ability to retain large amounts of moisture
Silt soils are well aerated

8. Loam Soils Contain sand, silt and clay in balance
Do not feel gritty when rubbed between the fingers
Have properties between sandy soils and clay soils
Usually well drained and well aerated
Have the ability to hold moisture and plant nutrients

9. Typical characteristics of a sandy loam:
Drainage and aeration
Free draining due to the relatively large particle size and the lack of water holding finer particles.
Easily leached (washed away) because water can move freely through it and it lacks a lot of the nutrient holding clay particles.
Free gas exchange results in good gaseous environment in the soil promoting good root growth and good mining of resources resulting in good growth

10. Water holding capacity
Large pore space allows water to drain freely to lower levels causing moisture stress in dry weather.
Reduces the rate of photosynthesis and poor structure due to reduced turgidity therefore less plant growth
Temperature
Warms quickly due to lack of temperature moderating moisture and free air movement.
Allows the soil to warm quickly resulting increased chemical reaction rate in roots and earlier plant growth in the spring

11. Typical characteristics of a clay loam:
Drainage and aeration
Poor drainage due to the small particle size and micropores. Water is held tightly so tends to retain nutrients.
Gas exchange is restricted in the soil preventing respiration in the roots.
Water holding capacity
Small pore spaces prevent water from draining freely preventing water stress in dry weather.
Temperature
Warms slowly because the temperature is moderated by moisture and lack of air movement.
Because the soil is slow to warm the sped of chemical reactions in roots is reduced and crops will be harvested later due to later planting (sowing) in the spring.

12. Below is a sample of garden loam magnified under the microscope
Below is a sample of garden loam magnified under the microscope. Copy the diagram and label: air spaces, coarse gravel, water, earthworm, fine sand, and dead organic matter.

13. Copy out the table below and fill it in correctly
SIZE GROUPING OF MINERAL PARTICLES IN SOIL
NAME PARTICLE DIAMETER
Bigger than 200 mm mm mm – 2mm – 0.2mm mm Less than 0.002mm
Write in the following names where you think they should go.
CLAY BOULDERS FINE SAND SILT GRAVEL COARSE SAND STONES

14. What do the following words mean?
Mineral Matter
Nutrients
Infertile
Light soils
Heavy soils
Leaching
Loam

15. SOIL REVISION QUESTIONS
Name the main components in soil.
Explain what the following terms mean
Chemical Weathering
Physical Weathering
Name three of the five factors that affect the rate of soil formation.
Define the following rock types.
Igneous
Sedimentary
Metamorphic