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RHS year 2 week 2 presentation
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RHS year 2 week 2 presentation

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  • 1. RHS Level 2 Certificate Year 2 Week 2 – Soil Texture, Structure and Cultivation
  • 2. Learning outcomes
    • 2.4 State the purposes of primary and secondary soil cultivations, including the addition of soil conditioners.
    • 3.1 Explain what is meant by ‘soil texture’.
    • 3.2 Describe the physical characteristics of the soil particles sand, silt and clay.
    • 3.3 Describe how the characteristics of each of the soil particles listed in 3.2 affect soils and their suitability for horticultural use.
    • 3.4 Explain what is meant by ‘soil structure’ (soil aggregates) and state how root establishment and growth are affected by different soil structures.
    • 3.5 State that a crumb soil is the ideal structure for horticultural use.
  • 3. Soil Texture - definition
    • Soil texture is the percentage of sand, silt and clay in a particular soil
    • Soil texture cannot be changed. 
  • 4. Soil particle sizes
  • 5. Soil Particles
    • Soil minerals exist as sand, silt and clay particles.
    Sand particles are big. Clay particles are small.
  • 6. Sand: big particles, big pores. Clay: little particles, tiny pores.
  • 7. Small particles, enormous surface area. Big particles, small surface area.
  • 8. Cation exchange capacity
    • Clay and humus have this property.
    • Negatively charged particles attract positively charged plant nutrients.
    • Available to plants, but not leached by draining water. Improves soil fertility.
    • ‘Exchange’ – one positively charged ion (like Hydrogen) can be swapped for another (like Calcium).
  • 9.  
  • 10. Soil Structure
    • Soil structure is the way in which soil particles are arranged into aggregates and the aggregates relate to each other
  • 11. Soil structure stability
    • Clay and humus act like glue in soil aggregates containing larger particles making them stable.
    • However soils with high clay content may not be stable. If they have low calcium content the aggregates will break down if compressed when wet. This leaves a solid mass.
    • Sandy soils with low levels of clay or humus are unstable; the aggregates break down easily into their component particles under compression or cultivation.
  • 12. Characteristics of soil types The best of all worlds. Structure is easily worked into crumb aggregates. Good CEC combined with good drainage and water holding capacity. Easy to work. Loam Quick to warm and cool. Drain freely, which makes them easy to work, but also prone to drought. Organic matter breaks down quickly. Very sandy soils can have unstable structures. Nutrients leach out as no CEC. Sandy soils Good water retention. Can be fertile. Easier to work. Unstable soil structure can lead to capping and water logging. Silt soils Warm slowly and cool slowly. High CEC so fertile. Retain high levels of water which can lead to working and drainage problems. Clay soils
  • 13. Cultivation types
    • Primary cultivation – digging (single or double), ploughing or rotavating.
      • Aerates the soil; incorporates organic matter; buries weeds and crop waste; exposes pests and allows weathering.
  • 14. Cultivation types
    • Secondary cultivation. Includes raking, treading to firm the soil and harrowing.
      • Produces a fine crumb-like structure
      • Firming allows good rooting by reducing large voids in the soil into which roots may grow and die off.
      • Levelling prevents run off of water and therefore erosion of fine soil particles.
      • To incorporate dry power or granular fertilizers evenly into the soil by raking.
  • 15. Learning outcomes
    • 2.4 State the purposes of primary and secondary soil cultivations, including the addition of soil conditioners.
    • 3.1 Explain what is meant by ‘soil texture’.
    • 3.2 Describe the physical characteristics of the soil particles sand, silt and clay.
    • 3.3 Describe how the characteristics of each of the soil particles listed in 3.2 affect soils and their suitability for horticultural use.
    • 3.4 Explain what is meant by ‘soil structure’ (soil aggregates) and state how root establishment and growth are affected by different soil structures.
    • 3.5 State that a crumb soil is the ideal structure for horticultural use.