CONTENTS 



INTRODUCTION 



Early uses of manures and the explanation of their action by the 

 alchemists ; Investigations prior to 1800 ; Work of De Saussure, 

 Davy, Thaer, and Boussingault ; Liebig's writings and their influ- 

 ence ; Investigations of Dawes and Gilbert ; Contributions of 

 other investigators ; Agronomy. Pages 1-9. 



CHAPTER I 



Physical Properties of Soils. — Chemical and physical properties 

 of soils considered ; Weight of soils ; Size of soil particles ; Clay ; 

 Sand ; Silt ; Form of soil particles ; Number and arrangement of 

 soil particles ; Mechanical analysis of soils. Soil types — 

 Potato and truck soils ; Fruit soils ; Corn soils ; Medium grass and 

 grain soils; Wheat soils. Relation of the soil to water ; Amount of 

 water required for crops ; Bottom water ; Capillary water ; Hydro- 

 scopic water; Loss of water by percolation, evaporation, and 

 transpiration ; Influence of cultivation upon the water supplv of 

 crops ; Capillary water and cultivation ; Shallow surface cultiva- 

 tion ; Cultivation after rains ; Rolling ; Sub-soiling ; Fall plowing ; 

 Spring plowing ; Mulching ; Depth of plowing ; Fertilizers and 

 their influence upon moisture content of soils ; Farm manures and 

 soil moisture ; Permeability of soils ; Drainage ; Relation of soils to 

 heat ; Heat from chemical reactions within the soil ; Heat and crop 

 growth ; Color of soils ; Odor and taste of soils ; Relation of 

 soils to electricity ; Importance of physical properties of the soil. 

 Pages 9-48. 



CHAPTER II 



Geological Formation and Classification of Soils. — Geological 

 study of soils ; Formation of soils ; Action of heat and cold ; 

 Action of water ; Glacial action ; Chemical action of water ; Ac- 



