CONTENTS. XV 



Losses of nitrogen incurred on the farm . . . .146 



Loss in treatment of farmyard manure . . . .146 



Nitrogen removed in milk . . . . . .147 



Economics of the nitrogen question . . . . .147 



Loss of nitrogen-compounds in the arts . . . .148 



Loss due to use of gunpowder . . . . . .148 



Loss due to sewage disposal . . . . . .149 



Our artificial nitrogen supply . . . . . .150 



Nitrate of soda and sulphate of ammonia . . . .150 



Peruvian guano . . . . . . . .151 



Bones 151 



Other nitrogenous manures . . . . . .152 



Oil-seeds and oilcakes . . . . . . .153 



Other imported sources of nitrogen ..... 153 



Conclusion ......... 153 



APPENDIX TO CHAPTER III. 



NOTE. 



I. Determination of the quantity of nitrogen supplied by 

 rain, as ammonia and nitric acid, to an acre of land 

 during one year ........ 155 



II. Nitrogen in soils at various depths . . . . .156 



III. Nitrogen as nitrates in cropped soils receiving no nitro- 



genous manures, in Ib. per acre (Rothamsted soils) . 157 



IV. Nitrogen as nitrates in Rothamsted soils . . .157 

 V. Examples of increase of nitrogen in Rothamsted soils 



laid down in pasture ....... 158 



VI. Loss by drainage of nitrates ...... 158 



VII. Examples of decrease of nitrogen in Rothamsted soils . 159 

 VIII. Amount of drainage and nitrogen as nitrates in drainage- 

 water from unmanured bare soil, 20 and 60 inches deep 160 



CHAPTER IV. NITRIFICATION. 



Process of nitrification . . . . . . . .161 



Occurrence of nitrates in the soil . . . . . .162 



Nitre soils of India . . . . . . . . .162 



Saltpetre plantations . . . . . . .163 



Cause of nitrification . . . . . . . .165 



Ferments effecting nitrification . . . . .167 



Appearance of nitrous organisms . . . . .168 



Nitric organism . . . . .169 



