B6e Summary

B6e Summary

1. Contents of Soil

   • complex mixture of
     • different sized minerals/particles
     • humus
       • formed by decomposition of dead organic material
     • water
     • air
   • supports diverse community
     • of living organisms
   • made of mineral particles
     • between them are air spaces
     • around them is a film of water

2. Types of Soil

   • sandy soil
     • large mineral particles
     • large air spaces
   • clay soil
     • small mineral particles
     • much closer together
   • loam
     • mix of sand and clay
     • large amount of humus

3. Tests for...

   • Water Content
     • 1. weigh, dry in a warm area and reweigh
       • 2. repeat until a constant mass is reached
         • 3. the difference is the mass of water in the original sample
           • (you can use this to work out a %)
   • Humus Content
     • 1. take a dried soil sample and weigh it
       • 2. heat it strongly with a bunsen burner to burn the humus
         • 3. the decrease in mass is equal to the amount of humus before
   • Air Content
     • 1. fill a can with soil and find the mass of the can with soil
       • 2. slowly add water to soak through the soil and fill air spaces
         • 3. when water reaches top of can find the new mass of the can, soil and water
           • 4. find the difference between the 2 masses, this is the mass of water added 1cm3 = 1g, which is also the amount of air

4. Life in the Soil

   • animals
     • Herbivores
       • feed on living plant matter
       • e.g. slugs, snails
     • Detrivores
       • feed on dead organic matter
       • e.g. earthworms, millipedes
         • Farmers buy worms and add them to soil to improve it, good for soil structure & fertility
     • Carnivores
       • feed on herbivores & detrivores
       • e.g. spiders, centipedes
   • plants
     • need soil for minerals, water and to anchor them
   • EARTHWORMS
     • aeration
       • burrows create gaps
       • increases 02 content in soil
     • drainage
       • burrows create gaps
       • reduces flooding
     • mixing
       • eats soil and passes waste elsewhere
       • nutrient distribution
     • making soil finer
       • release CaCO3 into gut to help digestion of leaves
       • easier for plants to grow
     • fertilising it
       • excretion
       • neutralises soil acidity