CONTENTS. 



CHAPTER I— Chemical Elements Needed by Plants 



and the Composition of Plants 1-12 



The Fifteen Elements. How Plants Feed. The Food 

 of the Plant. Composition of Plants. Amounts of 

 Water Used by Plants. Water in Young and Mature 

 Plants. Dry Matter of Plants. Composition of the 

 Dry Matter of Plants. Acids and Bases. Salts. Vari- 

 ation of Ash. Occurrence of Mineral Elements in 

 Plants. Distribution of Ash in Plants. Ash of Young 

 and Mature Plants. 



CHAPTER II— The Fertility of the Soil 13-24 



Composition of Soils. Factors Influencing Soil Fer- 

 tility. The Plant Food Supply. Plant Food Removed 

 by Some Crops. Plant Food not Available. The Es- 

 sential Elements. One Element Cannot Replace An- 

 other. Physical Condition of the Soil. Temperature. 

 Mechanical Composition. Surface Area of Soil Grains. 

 Lumpy Soil. Cracking of Soils. Puddling of Soils. 

 Freezing and Thawing. Plants are Benefited by Open 

 Soils. Plants Must Have Room. Plants Require 

 Oxygen. Drainage. Capillary Water. The Biological 

 Condition of the Soil. The Number of Bacteria in the 

 Soil. Nitrification. Denitrification. Organisms that 

 Gather Nitrogen. Inoculation of the Soil. 



CHAPTER III— Maintaining Soil Fertility 25-34 



Erosion and Ways to Check It. Loss of Fertility b}' 

 Drainage. Fallowing. Loss of Nitrogen by Continu- 

 ous Cropping. Losses of Phosphoric Acid and Potash. 

 One Crop Farming. Diversification and Rotation of 

 Crops. Make up of a Rotation. Reasons for Rotating 

 Crops. Rotation Keeps Down Weeds. Legumes are 

 Profitable. Rotation Helps to Distribute Farm Labor. 

 Rotation Helps to Check or Eradicate Insects and 

 Plant Diseases. It Furnishes Feed for Live Stock. It 

 Allows a Regular Income. It Prevents Losses of Fer- 

 tility. It Utilizes Plant Food More Evenly. It Saves 

 Fertilizer Expenditure. It Regulates the Humus Sup- 

 ply. System of Farming. 



