The Soil 
5 
C. CLAY SOILS 
These have above 80 per cent of the finer particles, 
which are also bound together by silicate of alumina. 
The obvious disadvantage of this is, that the water is 
retained in the soil, making it very cold in spring and 
also preventing the air from getting in to the roots of 
the plants. In periods of exceptional drought, also, it 
dries up, but in doing so 
it contracts to a consider- 
able extent, forming deep 
fissures, which break the 
roots of plants growing in 
it. This causes them to 
suffer to a great extent. 
And even when rain comes 
it is some considerable 
time before the plants reap 
any advantage from it; 
the water runs off the surface into these fissures, down 
into the subsoil, and then right away beyond the reach 
of the plant roots. Before any advantage can be gained, 
the soil must become thoroughly saturated. It then ex- 
pands, the fissures close up, and the plants get the benefit 
of the moisture. 
A clay soil, however, is often a very rich soil, espe- 
cially when “improved”. The first thing that must be 
considered in the improvement of a clay soil is to get 
rid of the superfluous moisture. This is done by drain- 
ing. A suitable depth for laying the drain pipes is from 
1 8 in. to 2 ft., according to the retentive power of the 
Tile Drain Pipe Drain 
