TILLAGE 137 



conserve this deep soil water by preventing it from moving 

 upwards too rapidly and escaping by evaporation from the 

 surface. In a previous chapter (page 104) we have de- 

 scribed the way in which this is done by shallow tillage. 



There is an old but truthful saying that it is possible to 

 water the garden with a rake. The dust mulch formed by 

 the rake makes the water below it last longer, so that it 

 does as much good as more rain from above. 



c. Tillage cleans the soil. A farmer must always keep 

 on the lookout for injurious agents like insects and weeds. 



A SCHOOL GARDEN. 

 Students making practical tests of soils. 



He must try not to allow them to become established in 

 his land. Many harmful insects pass the winter in the 

 ground on account of the protection it affords. During 

 the late fall, when these pests are at rest in fancied secur- 

 ity, the farmer may plow them up and leave them exposed 

 to the winter weather and spring birds. 



Weeds likewise are destroyed wholesale by tillage. 

 When the weed roots have become established in the soil, 

 the farmer inverts it by plowing, thus smothering the stems 

 of the weeds and exposing their tender roots to the dry, 

 withering air. And as this deep tillage kills mature weeds, 



