Soils
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Name the 5 components of soil.
Particles of weathered rock Water Air gaps Dead organic matter Biota (living things)
Name the three types of weathered rock found in soil from largest to smallest.
Sand, silt, clay
Name 3 examples of biota in soil.
Decomposers, plant roots, detritivores.
Soil needs to be fertile. What does fertile mean?
Contains all the things plants need for growth.
Name the 9 features of soil fertility.
Water content Air content Soluble inorganic nutrients Soil pH Dead Organic Matter Soil Biota Soil Texture Soil Depth Soil Structure
Name the three types of water found in soil.
Hygroscopic water, capillary water and gravitational water.
What is hygroscopic water?
Water adsorbed to soil particles, so is not available to plants.
What is capillary water?
Water close to soil particles, so it doesn’t drain easily and is available to plants.
What is gravitational water?
Water that drains easily, but is available to plant roots before this.
Why is air needed in soil?
To provide oxygen for aerobic reactions like respiration.
Name the three macronutrients needed in large amounts in soil.
Nitrogen in the form of NO3- Phosphorus in the form PO43- Potassium in the form K+”
Name three micronutrients needed in small amounts in soil.
Fe2+, Co2+, Cu2+, Mg2+, Mn2+
Why are positively charged nutrients more likely to be absorbed by plant roots?
Positively charged nutrients are attracted to negatively charged clay particles. These can be displaced by H+ and can then be absorbed by plants.
Why are negatively charged nutrients more likely to be leached (lost) from the soil?
Negatively charged nutrients are repelled from negatively charged clay particles. So are easily lost from the soil.
What occurs if soil pH gets too low?
Too high a concentration of H+ ions, so all nutrients get displaced from clay particles and leached.
What occurs if soil pH gets too high?
Too low a concentration of H+ ions, so nutrients are fixed to clay and are not available to plants.
Why does adding DOM increase soil fertility?
Will start to decompose, releasing nutrients to plants. Can also be a store of water and nutrients.
Give 2 reasons why deeper soil increases soil fertility.
Less likely to be waterlogged. Aids roots anchorage so plants less likely to blow over in high winds.
What is a ped?
The name for a clump of soil particles held together by sugars, fungi and plant roots.
What are the two types of peds?
Plate and Crumb
Describe the structure of plate peds.
Large and flat
Describe the structure of crumb peds.
Small and round
Describe the properties and fertility of soil with a plate ped structure.
Properties: poor drainage, aeration and root penetration. Fertility: Low
Describe the properties and fertility of soil with a crumb ped structure.
Properties: good drainage, aeration and root penetration. Fertility: High