14 



ELEMENTS OF FARM PRACTICE 



plants. Some of the starch formed in a plant is slightly 

 modified during the growth of the plant and forms fibrous 

 tissue and sugar. Examine kernels of wheat and corn 

 and a potato to see what a very large part is starch. The 

 white part of them all is very largely starch. It is seen 

 that by far the greater portion of our common plants does 

 not come from the soil, as is usually supposed, but is formed 

 from the poisonous gas, carbon dioxide, 

 from the air, and water from the soil. 

 Plant Food in the Soil. — A small por- 

 tion of every plant comes from the plant 

 food in the soil. A fairly good idea of the 

 proportion of any plant that is taken from 

 the soil is obtained by burning the plant, proxfmlte ^■^m'jfositfon 

 The ashes remaining represent nearly the sLlu^part If" the^gtjfen 

 whole amount that came from the soil, are composed of min- 

 This portion, though small, is absolutely tLMsUs loTpo^sld'^of 

 necessary for plant growth. One may afr^rnd'^iatll-^ ^'^""^ *^^ 

 liken the plant food taken from the soil to 

 salt eaten by animals. It furnishes a very small part of the 

 food required, but is absolutely necessary. Hence the impor- 

 tance of having a fertile soil that will furnish these sub- 

 stances as needed by the growing crop. 



Plants are able to get food from the soil only when 

 it is in a soluble form — that is, when the plant food will 

 dissolve in water as sugar dissolves in tea. 



Soluble Plant Food. — When a soil contains plenty of 

 soluble plant food it is said to be fertile. When plant 

 food becomes soluble in the soil it is dissolved in the soil 

 water. This water containing the plant food, surrounds 

 the fine roots and root hairs of the plant, and passes through 



their thin walls just as 

 nourishment enters the 

 blood vessels in the ani- 

 mal body. In this way 

 plants get their food, 

 soluble organic matter and 

 soluble mineral matter, 



Figure 4. — A diagram showing the compos- from the SOil. They take 

 NaJL'''^'^'''- From Minnesota Bulletin .^ ^^^ ^j^^^ ^^^^ ^.^j^ 



