Teaching Organic Farming and Gardening

Soil Physical Properties

36 | Unit 2.1
Demonstrations

Peat Moss DeMonstratIon

Detailed    Lecture Outline Reference:  C   11  d)  i.

PUrPOSE

To  show    how dry organic matter  repels  water

MATErIAlS

• Dry peat moss (a handful)

• Water

METhODS

Hold    up  a   handful of  dry peat    moss    and pour    

the water   over    it, showing how the water   runs    

off rather  than    soaking in.

sPonge DeMonstratIon

Detailed    Lecture Outline Reference:  C   12

PUrPOSE

To  provide a   conceptual  model   of  available   

water   capacity    and field   capacity

MATErIAlS

•    Sponge

•    Water  in  a   bowl    or  pan

METhODS

1.   Soak   the sponge  in  water   until   it  is  saturated.

2.   Hold   up  the sponge  until   most    of  the water   

stops   dripping.   Explain that    the sponge  is  

analagous   to  soil.   When    the water   has finished    

draining    from    the soil    24  hours   after   saturation, 

the soil    is  said    to  be  at  field   capacity.

3.   Squeeze    the sponge  to  remove  as  much    water   

as  you can.    Mention that    this    water   would   be  

analagous   to  what    can be  removed by  plants  

and is  called  available   water.  There   is  still   some    

moisture    in  the sponge  and that    is  analagous   to  

the water   that    is  held    so  tightly in  the soil    that    

plants  cannot  remove  it.