9 2 



THE FIRST BOOK OF FARMING 



To check loss of water by evaporation. 



To admit air to the roots of plants. Also to allow 

 air to act chemically on the mineral and organic 

 matter of the soil and make them available to the 

 crop. 



To raise the temperature of soils in the spring-, 

 or of damp soils at any time. 



To mix manures and organic matter with the soil. 

 The more thoroughly manure is distributed through 

 the soil the more easily plants will get it and the 

 greater will be its effect on the soil. 



To destroy the insect enemies of the plant by 

 turning them up to the frost and the birds. 



To kill weeds. Weeds injure crops: 



They waste valuable moisture by pumping it up 

 from the soil and sending it out into the air through 

 their leaves. In this way they do their greatest in- 

 jury to crops. 



They crowd and shade the crop. 



They take plant food which the plant should have. 



Spading and plowing bring about conditions nec- 

 essary for the sprouting or germination of seeds. 



Spading and plowing also tend to bring about 

 conditions necessary for the very important work 

 of certain of the soil bacteria. 



PARTS OF A PLOW 



It will be found that a good farm plow has the 

 following parts (Fig. 50) : 



A standard or stock, the central part of the plow 

 to which many of the other parts are attached. 



