SUMMARY. 
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2. It exposes the undersoil to the atmosphere, by which dormant plant 
food becomes active. 
3. It mixes the soils. 
4. it keeps soil open and porous, thus allowing the passage of the air 
and the young roots. 
5. It aids the capillary movement of water upwards in time of drought. 
6. It frees the ground of weeds. 
DRAINAGE (p. 92). 
Necessity for Drainage: 
1. To get rid of excess of water. 
2. To make room for air to enter the soil. 
3. To allow the soil to get warmed by the sun. 
4. To wash out sour and poisonous matter. 
Methods of Drainage : 
1. By trenches. 
2. By pipes or tiles laid underground. 
HOW WE ROB THE SOIL (p. 95). 
Exhaustion. — Plants sort out from the soil the plant-food they 
need. In time the “active” plant-food required is used up. Then the 
land is “ sick ” or “ exhausted ”. 
Remedies: 
1. Rest for the soil. Then some of the store of dormant plant-food 
will become active. This is why land is often left “ruinate ”. 
2. Change or rotation of crops. 
3. Manures, to add to the supply of active plant-food. 
4. Good tillage. 
HOW WE HELP TO FEED THE PLANTS (p. 99-101). 
Uses of Manure: 
1. To prevent exhaustion of soil by — 
(a) Adding plant-food. 
( b ) Acting on the dormant food. 
2. To restore fertility of exhausted soils. 
3. To supply necessary plant-food that is deficient in the soil. 
4. To improve texture by — 
(а) Loosening heavy soils. 
(б) Binding light soils. 
