xii CONTENTS 



CHAPTER PAGE 



VII. CHEMICAL METHODS OF DETERMINING ALKALI 81 



Preparing the Solution: from Moist Soil, from Dry Soil. De- 

 termining Total Solids. Carbonate and Bicarbonate Determina- 

 tion. Chloride Determination. Sulphate Determination. Nitrate 

 Determination. Analytical Process. Determination of Bases: 

 Calcium, Magnesium, Sodium. Other Methods of Determining 

 Soluble Salts: the Electrical Bridge, Freezing-point Method, 

 Biological Method. 



VIII. CHEMICAL EQUILIBRIUM AND ANTAGONISM 105 



Solubility of Alkali Salts. Mass Action. Absorption of Salts by 

 Soils. Equilibrium in Soil Solution. Antagonism between 

 Alkali Salts. 



IX. RELATION OF ALKALI TO PHYSICAL CONDITIONS IN THE SOIL 119 



Changing Soil Structure. Effect of Colloids. Hardpan. Effect 



on Moisture Movements. Evaporation of Moisture. 



X. RELATION OF ALKALI TO BIOLOGICAL CONDITIONS IN THE SOIL . 132 

 Relation of Soil Organisms to Fertility. Biological Inactivity 



and Soil Sterility. Concentrations of Alkali which Limit Biolog- 

 ical Activities. 



XI. MOVEMENT OF SOLUBLE SALTS THROUGH THE SOIL 141 



Salts in Natural Soils. Salt Movement with Water. Effect of 

 Water-table. Movement of Various Salts. Rate of Alkali 

 Movement. 



XII. METHODS OF RECLAIMING ALKALI LANDS 154 



The Source of Contamination. Reducing Evaporation. Plowing 

 under of Surface Alkali. Removing from Surface. Neutralizing 

 Sodium Carbonate. Other Chemical Treatments. Cropping 

 with Alkali-resistant Crops. Drainage. 



XIII. PRACTICAL DRAINAGE 167 



Advantages of Drainage. Determining the Need of Drainage. 

 Types of Drains. Cement Tile for Alkali Land: Preliminary 

 Survey, Laying out the System, Size of Drains, Construction 

 Methods. Outlets and Silt Basins. Cost of Drainage. 



XIV. CROPS FOR ALKALI LAND 192 



Factors Affecting Resistance. Economic Factors Affecting 

 Choice. Tolerance of Alkali by Various Crops; Forage Crops, 



