Chapter III: Position of Nitrogen in Agriculture

The Rothamsted experiments and the nitrogen question 115
Different forms in which nitrogen exists in nature 116
Relation of "free" nitrogen to the plant 117
Combined nitrogen in the air 118
Amount of combined nitrogen falling in the rain 119
Nitrogen in the soil 120
Nitrogen in the subsoil 121
Nitrogen of surface-soil 121
Amount of nitrogen in the soil 123
Soils richest in nitrogen 123
Nature of the nitrogen in the soil 124
Organic nitrogen in the soil 125
Differences of surface and subsoil nitrogen 126
Nitrogen as ammonia in soils 127
Amount of ammonia in soils 127
Nitrogen present as nitrates in the soil 128
Position of nitric nitrogen in soil 128
Amount of nitrates in the soil 129
Amount of nitrates in fallow soils 129
Amount of nitrates in cropped soils 130
Amount of nitrates in manured wheat-soils 131
The sources of soil-nitrogen 131
Accumulation of soil-nitrogen under natural conditions 133
Accumulation of nitrogen in pastures 134
Gain of nitrogen with leguminous crops 135
The fixation of "free" nitrogen 136
Influence of manures in increasing soil-nitrogen 136
Sources of loss of nitrogen 137
Loss of nitrates by drainage 137
Prevention of loss of nitrogen by permanent pasture and
"catch-cropping" 138
Other conditions diminishing loss of nitrates 139
Amount of loss of nitrogen by drainage 140
Loss of nitrogen in form of "free" nitrogen 141
Total amount of loss of nitrogen 142
Loss of nitrogen by retrogression 142
Artificial sources of loss of nitrogen 144
Amount of nitrogen removed in crops 144
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
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 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