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ROCKS AND SOIL 



Elements Used by Plants. There are a number of 

 elements that are found necessary for the growth of plants. 

 Three of these, carbon, nitrogen, and oxygen, are found 

 in the air, while phosphorus, potassium, magnesium, 

 calcium, iron, and sulphur are found in soils. In order 

 for plants to grow, these elements must be in the form 

 of soluble compounds so that they can be absorbed 

 through the roots of the plants. Iron aids in making 

 the leaves green. Potassium helps the plant to make 

 food substances. Phosphorus helps the root to grow 

 and seed to ripen. Calcium aids the roots by separating 

 the substances in the soil from other materials so that 

 they can be readily absorbed. Nitrogen is necessary 

 because of the relatively large amount used in the living 

 matter of plants. 



Acid and Alkaline Soil. In the far West, alkali soil is 

 often found, especially in desert regions. If such regions 

 get water through irrigation and are used for agriculture, 

 as much as possible of the alkali must be removed from 



Wright Pierce 



This is a dried-up lake bed which is impregnated with alkali. In the rainy season 

 this is a lake so impregnated with alkali that the water is not fit for use. 



