OUTLINE OF CHAPTER IV. 



THE SOIL AS RELATED TO PLANTS. 



/^,— USES OF THE SOIL TO PLANTS. 

 I. It Serves as a Foothold. 

 II. It Affords Plant-food. 



III. It Acts as a Storehouse for Water. 



IV. It Retains and Regulates the Heat. 



V. It Serves as a Habitation for Soil Bacteria 



i?.— CONSTITUENTS OF PLANTS. 



I. Chemical Analysis of Plants. 



II. Sources of Plant-food. 



1. Air -derived Eletnents. 



(i) Carbon. 



(2) Oxygen. 



(3) Hydrogen. 



(4) Nitrogen. 



2. Soil-derived Elements. 



(i) Phosphorus. 

 (2) Potassium. 



C— FERTILITY OF THE SOIL. 

 I. Chemical Analysis of Soils. 



II. Vegetation Experiments. 



III. Fertilization of the Soil. 



I. Commercial Fertilizers. 



(i) Nitrogenous Compounds. 

 (2) Phosphorous Compounds. 



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