86 ELEMENTARY AGRICULTURE 



Plant Food. In order that plants may grow, they 

 need certain foods that we call plant foods. Plants 

 get this food from the soil and the air. In order 

 not to rob the soil, we must know what our crops 

 are taking out of it and how to put these plant 

 foods back. 



Plants Need Many Foods. The plant needs a 

 variety of foods, just as a hungry boy does. Ordi 

 nary plants need about thirteen different kinds. 

 Some of these elements, or different kinds of foods, 

 are obtained from the air, and others from the soil. 

 To grow good crops, the soil must not only have 

 enough of all the foods that the plants need, but 

 they must- be in such form that the roots can take 

 them up and use them to build up the stalk, leaves, 

 and fruit. 



Only Liquid Food. The foods taken from the soil 

 are called mineral foods, because they are actually 

 bits of minerals dissolved in water just as you dis- 

 solve sugar or salt. Plants drink their food through 

 tiny, hollow root hairs that take up this water solu- 

 tion. They cannot take up solid particles of soil. 

 So all this mineral plant food must be dissolved in 

 water before it can pass into the plant and become a 

 part of it. 



Water the Chief Plant Food. When soil is 

 perfectly dry, plants cannot grow in it, for water 

 generally forms about three-fourths of a plant's 

 weight. Since the plant can take plant food from 

 the soil only in liquid form, we see that water itself 



