FOOD THE PLANT TAKES FROM THE SOIL 57 



about the following amounts of water: Oats, 376 pounds 

 of water to one pound of dry matter ; wheat, 338 pounds 

 of water to one pound of dry matter; red clover, 310 

 pounds of water to one pound of dry matter. Take as 

 an example the clover crop already mentioned, which 

 weighed 12,000 pounds. As 80 per cent of this is 

 water, we have 20 per cent dry matter, or 2,400 pounds. 

 If one pound of dry matter requires 310 pounds of 

 . the 2,400 pounds must require 744,000 pounds 

 «>f water, or 372 tons, or about 75,000 gallons. At this 

 rate, to prod nee about one ton of clover hay more than 

 300 tons of water are needed. 



The moisture in the atmosphere cannot be taken up 

 by plants unless it first passes into the soil. 



A plant wilts because the leaves give off more water 

 than the rootl Can supply. 



57. Nitrogen. — From the soil plants draw most of 

 their supplies of nitrogen which is combined in the 



ic matter of the soil. Nitrogen, if not the most 

 important, ia one of the mo<t important of all the 

 plant foods, and we shall hav 3 more to say about it when 

 we come to write of soils. 



58. Mineral Matter. — The elements which make np 

 the ashes of plants eon . from the soil, as 

 they an not found in the stmosphere or largely in 

 water. Although the amount of mineral matter con- 



; in plants is wry small, a proper supply is abso- 

 lutely necessary. All soils contain the necessary ele- 



- of plant food, but in many soils the supply is 

 small, and in some soils the elements are so combined 

 as to be unfit for plant food. When such is the case 



