Soil Composition and Properties
Introduced| English |
|---|
| texture/ˈtekstʃə/ |
| sand/sænd/ |
| silt/sɪlt/ |
| clay/kleɪ/ |
| loam/ləʊm/ |
What soil is made of
- Not all soil is the same — some is gritty, some sticky, some smooth.
- The difference comes from the size of its particles.
- Particle size decides how soil holds water and feeds plants.
- Getting the mix right is the key to good farmland.
Three particle sizes
- Soil texture 质地 depends on the mix of three particle sizes.
- Sand 砂粒 particles are the largest and grittiest.
- Silt 粉粒 particles are medium, smooth like flour.
- Clay 黏粒 particles are the tiniest of all.
Soil texture is determined by…
Soil texture comes from the proportion of sand, silt, and clay it contains.
How texture affects water
- Big sand particles leave big gaps, so water drains through fast.
- Tiny clay particles pack tightly, holding water and nutrients — but can waterlog.
- Silt sits in between.
- Texture also sets a soil's permeability — how easily water passes through.
Sandy soil, with large particles, tends to…
Big sand particles leave big gaps, so water drains through quickly.
The smallest particles, which hold water tightly, are ____.
Clay particles are tiny with tiny gaps, so they hold water and can waterlog.
The ideal soil: loam
- Loam 壤土 is a balanced mix of sand, silt, and clay.
- It drains well enough to avoid waterlogging.
- Yet it still holds enough water and nutrients for roots.
- This balance makes loam the best soil for most crops.
Sort the soil particles
Sort each soil particle by its size - the mix of sizes gives a soil its texture and properties.
Loam, a balanced mix of sand, silt, and clay, is ideal for most plants.
Loam drains well but still holds water and nutrients — the best of both worlds for crops.
Select all true statements about soil properties.
Soils vary enormously in texture and properties. The other three are correct.
Neither pure sand nor pure clay is good farmland. Pure sand drains too fast and holds no nutrients; pure clay holds water so tightly it waterlogs and starves roots of air. The best soils, like loam, are a balance of all three particle sizes.
Watering a sandy versus a clay pot:
- Pour water on sandy soil and it runs straight through — plants can dry out.
- Pour the same water on clay soil and it sits on top, then waterlogs the roots.
- Loam soaks up the water and holds just enough — which is why gardeners prize it.
Soil texture depends on the mix of sand (large, fast-draining), silt (medium), and clay (tiny, water-holding) particles. Texture controls how soil holds water and nutrients. A balanced mix — loam — drains well yet holds enough water, making it ideal for most plants.