CONTENTS 



CHAPTER VI 



CULTIVATION AND THE MOVEMENTS OF SOIL 

 WATER 



PAOJB 



Nature of the Film of Liquid surrounding Wet Particles of 

 Soil. Retention and Movements of Water due to 

 Surface Tension. Percolation. Rise of Subsoil Water 

 by Capillarity. Value of Autumn Ploughing. Effect 

 of Spring Cultivations. Cooling of the Land by 

 Evaporation. Effect of Hoeing and Rolling upon the 

 Temperature and Water-content of the Soil. Dry 

 Farming in Semi-arid Regions. Drainage and the 

 Temperature of Soils. Spring Frosts. Early and 

 Late Soils lOO 



CHAPTER Vn 



THE LIVING ORGANISMS OF THE SOIL 



Formation of Nitrates in the Soil. Bacteria in the Soil 

 which decompose Organic Matter. Bacterial Loss of 

 Nitrogen from the Soil. Formation of Humus. Fixation 

 of Nitrogen by Bacteria associated with Leguminous 

 Plants. Value of Clover Crops in the Rotation. In- 

 oculation of Soil. Other Bacteria-fixing Nitrogen in 

 the Soil. Accumulation of Nitrogen in Virgin Soils. 

 Dependence of Soil Fertility upon Bacteria . .120 



CHAPTER Vni 



THE CHEMICAL COMPOSITION OF THE SOIL 



Plant Food found in Normal Soils. Dormant and Available 

 Plant Food. Rotations and Plant Food in the Soil. 

 Systems of Farming— Wasteful and Conservative. 

 Requirements of Different Crops for Fertilisers. Types 

 of Soil— Characteristic Weeds and Crops . . I49 



