1.2 Properties of soil

• Physical properties of soil: texture, structure, porosity and colour
• Chemical properties of soil: pH and nutrients
• Biological properties of soil: humus and living organisms
• The soil profile and its importance in crop production
• Kenyan soils: black cotton, red loam and sandy coastal soils
• Investigating soil properties: jar test, pH and humus
• How soil properties influence maize and sukuma wiki

• describe the physical, chemical and biological properties of a soil for crop production
• investigate the properties of soil for crop production
• relate the importance of the soil profile to crop production
• acknowledge the importance of soil properties in crop production

“How do the properties of soil influence crop production?”

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1. Soil properties that make a crop
   40 min · 1 practice tasks · quiz
   Soil is more than dirt: physical, chemical and biological properties together decide whether maize or sukuma will grow.
2. Soil texture: sand, silt, clay and loam
   40 min · 1 practice tasks · quiz
   Texture is the mix of sand, silt and clay. It decides drainage, workability and how a maize or sukuma bed behaves.
3. Soil structure: crumbs that roots can use
   40 min · 1 practice tasks · quiz
   Structure is how particles clump. Crumbs help maize. Plates and massive clods block air, water and roots.
4. Porosity, drainage and water the crop can use
   40 min · 1 practice tasks · quiz
   Pores hold air and water. Sandy soils empty fast; clays stay wet. Roots need both air and a drink.
5. Soil colour: a field clue, not a full test
   40 min · 1 practice tasks · quiz
   Dark, red, pale and grey-mottled colours hint at humus, iron, leaching or waterlogging. Confirm with feel, pH and a crop.
6. Soil pH: the chemical window for roots
   40 min · 1 practice tasks · quiz
   pH is acidity or alkalinity. Most crops, including maize and sukuma, prefer about 6 to 7. Wrong pH locks nutrients.
7. Soil nutrients: N, P, K and the rest
   40 min · 1 practice tasks · quiz
   Nitrogen, phosphorus and potassium do different jobs in maize and sukuma. Manure feeds many nutrients; fertiliser tops up the short ones.
8. Humus: the heart of a fertile topsoil
   40 min · 1 practice tasks · quiz
   Humus is well-decayed organic matter. It holds water and nutrients, builds crumbs, and darkens the A horizon.
9. Soil organisms: the workers you rarely see
   40 min · 1 practice tasks · quiz
   Earthworms, bacteria and fungi turn residues into plant food and open the soil. Living soil stays fertile.
10. The soil profile and the crop layer
    40 min · 1 practice tasks · quiz
    A profile is a vertical section through soil. Crops live in the A horizon. Depth, colour and a wet B decide maize and sukuma.
11. Kenyan soils: black cotton, red loam, sandy coast
    40 min · 1 practice tasks · quiz
    Three common Kenyan soils farm differently. Match maize and sukuma, and the jembe, to the soil you have.
12. Investigate: jar, pH, humus - then maize and sukuma
    40 min · 1 practice tasks · quiz
    Carry out jar, pH and humus tests on a local sample, then judge whether maize and sukuma would like that soil and what to change.