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 phosphoric acid removed in milk 207 Loss of phosphoric acid in treatment of farmyard manure 208 Loss of phosphoric acid in sewage 208 Sources of artificial gain of phosphoric acid 208

APPENDIX TO CHAPTER V.
NOTE
I. Composition of apatite (Voelcker) 210
II. Percentage of phosphoric acid in the commoner rocks 211

CHAPTER VI.--POSITION OF POTASH IN AGRICULTURE.

Potash of less importance than phosphoric acid 212 Occurrence of potash 213 Felspar and other potash minerals 213 Stassfurt salts 214 Occurrence of saltpetre 215 Occurrence of potash in the soil 215 Potash chiefly in insoluble condition in soils 216 Percentage of potash in plants and plant-ash 216 Occurrence of potash in animal tissue 217 Sources of loss of potash 217 Amount of potash removed in crops 218 Amount of potash removed in milk 218 Potash manures 218

APPENDIX TO CHAPTER VI.
NOTE
I. Amount of potash in different minerals 220
II. Quantity of potash obtained from 1000 lb. of different
kinds of vegetation in the manufacture of potashes 220

PART III.--MANURES.