LIVESTOCK FARMING 39 



does it hold much water. AVater runs through it as through 

 a willow basket. 



Aeration is another important advantage in cultivation. 

 The air fills the spaces between the loosened soil particles and 

 this brings oxygen to the roots of the plants. Oxygen is an 

 important plant food just as it is important to animal life. 



Cultivation also kills weeds. The importance of this is well 

 recognized. 



In almost any system of livestock farming in nearly every 

 part of the world where livestock is grown, corn is used as 

 one of the principal feeds. If corn is to be grown successfully 

 it must be cultivated. It must also be cultivated during the 

 summer. This is beneficial to the soil in all the ways men- 

 tioned, and especially in the killing of weeds and in the 

 preservation of bacteria. 



Summer fallowing is beneficial because the soil is culti- 

 vated, but when the soil is cultivated in the corn field it is 

 doubly beneficial because the shade from the corn plant pro- 

 tects the bacteria in the soil. Therefore, a crop of wheat may 

 yield as much after a corn corp as after summer fallowing. 

 The corn crop is thus clear profit. 



Humus. — The value of humus in the soil was discussed in 

 Chapter I and need not be repeated here. It furnishes plant 

 food, produces a sponge for holding water and allows more 

 bacteria to develop. Livestock farming puts more humus into 

 the soil than does grain farming. 



The grass and legume crops leave more roots in the soil than 

 most grain crops and these as well as corn shade the soil dur- 

 ing the summer to prevent the burning out of the humus in the 

 soil by the sun. 



Leguminous Plants. — With a system of livestock farming, 

 also, it is possible to introduce more leguminous plants, such 

 as clover, alfalfa, soy beans, and peas. These, to put it 

 popularly, take nitrogen, one of the principal plant foods, 

 from the air and leave some of it in the soil for the next gen- 

 eration of plants. The nitrifying bacteria, as they are called, 

 live upon the roots of the leguminous plants and for their 

 own life take nitrogen from the air. Then when they die, 

 the nitrogen is available for other plants. These bacteria 



