Figure 9.15: Hydrangeas.- Soil Structure: the decomposed organic matter, called humus gives topsoil its dark
colour. It supplies plants with nutrients and helps the soil retain water. Soils rich in
humus are fertile soils. The specific soil type is determined by the size of particles e.g
sand has very large sized particles, clay has very small sized particles and loam has a
mixture of particle sizes. If you moist soil between your fingers, clay soil feels sticky,
sandy soil feels gritty and loam soil feels soapy. The water retention capacity of soils is
the ability of soil to retain different amounts of water. Clay soil retains a large amount
of water. Sandy soil retains very little water. Loam soil retains a moderate amount of
water.
Investigation:
Aim:
To investigate the water retaining properties of three soil types and the rate at which the
water flows through the soil samples.
Apparatus:
loam, sand and clay soil samples
filter funnels and filter paper
measuring cylinders
water
stop watches
Method:
- Set up the three different measuring cylinders each with a funnel and filter paper in the
funnel. - Label each of the measuring cylinders either loam, sand, clay
- Add the same amount of soil sample to the labelled measuring cylinder.
- Carefully pour the same amount of water into each funnel.
Chapter 9. Biospheres to ecosystems 271