xii CONTENTS 



CHAPTER IV 



TILLAGE AND THE MOVEMENTS OF SOIL WATER 



PAOB 



Water required for the Growth of Crops — The Effect of 

 Drainage — Effects of Autumn and Spring Cultivation, 

 Hoeing and Mulching, Rolling, upon the Water Con- 

 tent of the Soil— The Drying Effect of Crops— Bare 

 Fallows — Effect of Dung on the Retention of Water by 

 the Soil • • . • , . 89 



CHAPTER V 



THE TEMPERATURE OF THE SOIL 



Causes affecting the Temperature of the Soil — Variation 

 of Temperature with Depth, Season, etc. — Tempera- 

 tures required for Growth — Radiation — Effect of Colour 

 — Specific Heat of Soils — Heat required for Evapora- 

 tion — Effect of Situation and Exposure — Early and Late 

 Soils. ••••••• 120 



CHAPTER VI 



THE CHEMICAL ANALYSIS OF SOILS 



Necessary Conventions as to the Material to be Analysed 

 — Methods Adopted — Interpretation of Results — Dis- 

 • tinction between Dormant and Available Plant Food 

 — Analysis of the Soil by the Plant — Determination 

 of "Available" Phosphoric Acid and Potash by the 

 Use of Weak Acid Solvents .... 139 



CHAPTER VII 



THE LIVING ORGANISMS OF THE SOIL 



Decay and Humification of Organic Matter in the Soil — 

 Alinit — The Fixation of Free Nitrogen by Bacteria 

 living in Symbiosis with Leguminous Plants — Soil 

 Inoculation with Nodule Organisms— Fixation of Nitrogen 

 by Bacteria living free in the Soil — Nitrification — 

 Denitrification — Iron Bacteria — Fungi of Importance 

 in the Soil : Mycorhiza, and the Slime Fungus of 

 " Finger-and-Toe " . .  • . .168 



