Manures and the principles of manuring

IV. Effect of urine on nitrification in soils 197

V. Solution used by Professor Frankland in cultivating nitrificative micro-organisms 198

VI. Experiments by Boussingault on rate of nitrification 198

VII. Nitrogen as nitrates in Rothamsted soils after bare fallow in lb. per acre 198

* CHAPTER V.--POSITION OF PHOSPHORIC ACID IN AGRICULTURE.

Occurrence of phosphoric acid in nature 199

Mineral sources of phosphoric acid 200

Apatite and phosphorite 200

Coprolites 201

Occurrence of phosphoric acid in guanos 202

Universal occurrence in common rocks 202

Occurrence in the soil 203

Condition in which phosphoric acid occurs in the soil 203

Occurrence in plants 204

Occurrence in animals 205

Sources of loss of phosphoric acid in agriculture 205

Loss of phosphoric acid by drainage 206

Artificial sources of loss of phosphoric acid 206

Amount of