«V CONTENTS 



CHAPTER VIII 



PERUVIAN GUANO AND OTHER MIXED 

 FERTILISERS 



Origin of the Deposits of Guano — Variation in Composition p*^°« 

 with Age — Compounds of Nitrogen present in Peruvian 

 Guano — Ichaboe and Damaraland Guanos — Fish 

 Guano — Meat Guano — Dried Blood — Greaves — Rape 

 Dust and other Cake Residues — Manures derived from 

 Faecal Matter — Sewage Sludges .... 229 



CHAPTER IX 



MATERIALS OF INDIRECT FERTILISING VALUE 



Lime — Early Use of Lime — White and Grey Limes — Lime 

 Ashes — Marl — Chalk — Ground Limestone — Indications 

 of the Lack of Lime in the Soil — Action of Lime upon 

 the Soil — Improvement of Texture — Promotion of the 

 Oxidation of nitrogenous Residues in the Soil — Increase 

 in the Availability of Phosphoric Acid and Potash — 

 General Action of Soluble Salts on the Soil — Gas 

 Lime — Gypsum — Salt — Sulphate and Carbonate of 

 Magnesia — Sulphate of Iron ; Supposed Connection of 

 Iron in the Soil with the Colour of Fruit and Flowers — 

 Manganese Salts — Silicates — Green Manuring — Folding 

 Catch Crops on the Land ..... 249 



CHAPTER X 



THEORIES OF FERTILISER ACTION 



Liebig's Ash Theory — Part played by the Soil in the Nutrition 

 of the Crop — Ville's Theory of Dominants — Liebig's 

 Law of the Minimum — Law of diminishing Returns — 

 Limiting Factors in Plant Growth — Is the Composition 

 of the Soil Water unaffected by Fertilisers ? — Attack of 

 the Plant's Roots upon Insoluble Fertilisers — The Part 

 played by Carbon Dioxide in the Soil — Excretion of 

 Toxic Substances from Plant Roots — Rotations as a 

 Substitute for Fertilisers — Unexplained Factors in the 

 Nutrition Problem ...... 276 



