What is soil fertility?
Soil fertility is the soil’s ability to support plant growth and ensure high crop yields.
What makes up a fertile soil?
Supplies essential nutrients 🌾
Retains moisture without waterlogging 💧
Supports diverse soil biota 🐛
Allows root penetration 🌱
What are the sizes of each soil particles?
Sand: Largest particles, large air spaces
Silt: Medium size
Clay: Smallest particles, small air spaces
What do plants need water for?
*Absorb dissolved nutrients like nitrates and phosphates
*Carry out photosynthesis
*Maintain cell stability
What soils are best for water retention and which are not?
-Sandy soils: Excellent drainage but may lose nutrients quickly
-Clay soils: Retain water well but prone to waterlogging
-Silty soils: Best balance of moisture retention and drainage ✅
How does the high specific heat capacity of water affect soil temperatures?
*Clay soils stay cooler and fluctuate less – can reduce enzyme activity in soil biota
*Sandy soils warm up and cool down faster
How does aeration differ in different soil textures and why are aerated soils important?
Good aeration supports aerobic respiration and nitrification.
*Sandy soils: Well-aerated
*Clay soils: Poor aeration, more prone to anaerobic conditions → denitrification increases, reducing fertility
How does soil texture impact root penetration?
Sandy soils: Easy root growth
Clay soils: Difficult for roots to penetrate, reducing plant support and nutrient recycling
What are the roles of soil biota e.g. detritivores, decomposers and nitrifying bacteria
Breaking down organic matter into nutrients (humus)
Aerating soil via burrowing
Supporting nutrient cycles (e.g. nitrogen cycle)
Soils need to be aerated, moist, and rich in organic matter to support a thriving biotic community.
What is the difference between soil structure and soil texture?
Soil texture = Proportions of sand, silt, and clay
Soil structure = How soil particles clump into aggregates (peds)
Crumb peds: Round, small → high fertility ✅
Platy peds: Flat, compacted → low fertility ❌
What is the ideal soil pH and the impacts if it becomes too acidic/alkaline?
*Ideal soil pH for fertility: 5.5 to 7.0
Too acidic:
Damages root hair cells
Increases solubility of nutrients (↑ leaching risk)
Too alkaline:
Phosphates become insoluble, unavailable to plants
Why is it beneficial to have deeper soils?
Better water retention, root anchorage, and plant support
More likely to maintain stable growing conditions
