Other nitrogenous manures
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152
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|
|
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 nitrogenous manures, in lb. 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 pastures
|
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
|
|
|
Difficulty in isolating them
|
169
|
|
|
Nitrifying organisms do not require organic matter
|
169
|
|
Conditions favourable for nitrification—
|
|
|
Presence of food-constituents
|
170
|
|
|
Presence of a salifiable base
|
171
|
|
|
Only takes place in slightly alkaline solutions
|
172
|
|
|
Action of gypsum on nitrification
|
173
|
|
|
Presence of oxygen
|
173
|
|
|
Temperature
|
175
|
|
|
Presence of a sufficient quantity of moisture
|
176
|
|
|
Absence of strong sunlight
|
176
|
|
|
Nitrifying organisms destroyed by poisons
|
176
|
|
Denitrification
|
177
|
|
|
Denitrification also effected by bacteria
|
178
|
|
|
Conditions favourable for denitrification
|
178
|
|
|
Takes place in water-logged soils
|
179
|
|
Distribution of the nitrifying organisms in the soil
|
179
|
|
|
Depth down at which they occur
|
180
|
|
|
Action of plant-roots in promoting nitrification
|
181
|
|
|
Nature of substances capable of nitrification
|
181
|
|
Rate at which nitrification takes place
|
183
|
|
|
Nitrification takes place chiefly during summer
|
183
|
|
|
Process goes on most quickly in fallow fields
|
184
|
|
|
Laboratory experiments on rate of nitrification
|
185
|
|
|
Certain portions of soil-nitrogen more easily nitrifiable than the rest
|
187
|
|
|
Rate of nitrification deduced from field experiments
|
