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
|
187
|
|
|
Quantity of nitrates formed in the soils of fallow fields
|
188
|
|
|
Position of nitrates depends on season
|
188
|
|
|
Nitrates in drainage-waters
|
188
|
|
|
Amount produced at different times of year
|
189
|
|
|
Nitrification of manures
|
190
|
|
|
Ammonia salts most easily nitrifiable
|
191
|
|
|
Sulphate of ammonia the most easily nitrifiable manure
|
191
|
|
|
Rate of nitrification of other manures
|
192
|
|
|
Soils best suited for nitrification
|
|
