OUTLINE OF CHAPTER IV. 



THE SOIL AS RELATED TO PLANTS. 



A. 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 



A CONSTITUENTS OF PLANTS. 



I. Chemical Analysis of Plants- 



II. Sources of Plant-food. 



1. Air-derived Elements. 



(1) CARBON. 



(2) OXYGEN. 



(3) HYDROGEN. 



(4) NITROGEN. 



2. Soil-derived Elements, 



(1) PHOSPHORUS. 



(2) POTASSIUM. 



C.-FERTILITY OF THE SOIL. 

 I. Chemical Analysis of Soils. 



II. Vegetation Experiments. 



III. Fertilization of the Soil. 



i. Commercial Fertilizers. 



(1) NITROGENOUS COMPOUNDS. 



(2) PHOSPHOROUS COMPOUNDS. 



