CONTENTS vii 



XVIII. CONTROL OF MOISTURE. I. DRAINAGE 222 



Removal of Excess of Water Stability Granulation 

 Available Moisture Aeration Temperature Decompo- 

 sition and Nitrification Heaving Erosion Types of 

 Drainage Open Drains Tile Drains. 



XIX. CONTROL OF MOISTURE. II. TILLAGE 230 



Moisture Capacity of Soils Excess of Moisture Losses 

 from Soils Artificial and Soil Mulches Fineness of 

 Mulch Depth of Mulch Maintenance of Mulch. 



XX. CONTROL OF MOISTURE. III. DRY-LAND AGRICULTURE 238 



Adaptation of a Region to Dry Farming -Water Require- 

 ments of Plants Loss of Water Method of Preventing 

 Loss of Water Tillage System of Cropping Crops for 

 Dry Farming Seeding Acclimated Seed. 



XXI. CONTROL OF MOISTURE. IV. IRRIGATION 257 



Area and Projects Sources of Water Preparation of 

 Land for Irrigation Character of Water Used for Irriga- 

 tion -Composition of River Sediments Time of Irrigation 

 Amount of Water to Apply Loss of Water from Canals 

 Duty of Water Duty of Water in Different Countries 

 Measurement and Distribution of Water Methods of 

 Irrigation Cultivation after Irrigation Crops for Irri- 

 gated Lands Irrigation in Humid Climates. 



XXII. ALKALI LANDS AND THEIR RECLAMATION 278 



Origin of Alkali Kinds of Alkali Effect on Physical 

 Condition of Soil Vertical and Horizontal Distribution 

 Effect of Irrigation on Rise of Alkali Effect of Alkali on 

 Plants Limit for Germination and Growth Utilization 

 and Reclamation of Alkali Lands Growing Alkali- 

 resistant Crops Retarding Evaporation Deep Plowing 

 and Turning Under Alkali Neutralizing Black Alkali 

 Removing the Salts from the Soil Hardpan Value of 

 Alkali Land Alkali Soils of Humid Regions. 



XXIII. TEMPERATURE 293 



Sources of Soil Heat Direct Radiation from the Sun 

 Precipitation Chemical Changes Physical Changes 

 Loss of Heat -Radiation Conduction into the Soil 

 Evaporation of Water -Convection Currents of Air -Soil 

 Temperature for Vital Functions of Plants Tempera- 

 ture for Germination Temperature for Growth -Tem- 

 peratures Favorable for Osmosis and Diffusion Tempera- 

 tures for Nitrification -Conditions Affecting Soil Tempera- 

 ture Specific Heat 'Evaporation of Water Drainage - 

 Presence of Water -Absorption and Radiation of Heat- 

 Latitude or Angle of Sun's Rays Conductivity of Soil 

 Material and Soils Tillage. 



XXIV. SOIL AIR AND AERATION 309 



Use of Air in Soils -Amount of Air in Soils Composition 

 of Soil Air Aeration or Soil Ventilation Water-logged 

 Soil Running Together. 



