n, percentage of, 343;
not an exhausting manure, 345;
origin of fields of, 334;
properties of, 343;
quantity to apply, 348;
shipments of, 351;
soils benefited by, 348;
source of
nitrogen, 150;
top-dressing with, 344.

Nitrates, amount lost by drainage, 140;
amount produced at different times, 189;
amount in soil, 129;
conditions diminishing loss of, 139;
constantly formed in soil, 138;
in barley-soils, 158;
in cropped soils, 130, 157;
in drainage-waters, 160, 188;
in fallow-soils, 129;
in manured wheat-soils, 131, 157;
in soil, 129, 162;
lost by drainage, 137;
most formed in summer, 139;
nitrogen as, in Rothamsted soils, 198;
position of, in soil, 188;
quantity formed in fallow-fields, 188.

Nitre, beds, 163;
occurrence of, 162;
soils of India, 162.

Nitric acid, amount of, supplied to soil by rain, 155;
derived from sea weed, 337;
formed from ammonia, 118;
formed from nitrous acid, 168;
in farmyard manure, 259;
in soil, 128;
lost in mixing manures, 536;
most important nitrogen compound for plants, 161;
relation of, to plants, 50;
source of, in nitrate of soda, 337.

Nitrification, 51, 52, 161-198;
action of gypsum on, 173;
alkalinity necessary for, 172;
in asparagin, 182;
bearing of, on agriculture, 193;
in bones, 182;
cause of, 165;
conditions favourable for, 170;
denitrification, 177-179;
effected by micro-organisms, 51, 167;
in ethylamine, 182;
in fallow-fields, 184;
food-constituents necessary for, 170;
field experiments on rate of, 187;
in gelatin, 182;
in horn, 182;
laboratory experiments on rate of, 185;
in manures, 190, 192;
in milk albuminoids, 182;
mineral salts necessary for, 52;
moisture necessary for, 52, 176;
old theories on, 196;
organic matter not necessary for, 169, 196;
oxygen necessary for, 52, 173;
plant-roots promote, 181;
in rape-cake, 182;
rate of, 183;
rotation of crops, bearing of, on, 195;
soil best suited for, 192;
in subsoils, conditions favourable for, 181;
substances capable of, 181;
in summer, 183;
sunlight, effect of, on, 176;
temperature necessary for, 52, 175;
in thiocyanates, 182;
in urea, 182;
in wool, 182.

Nitrifying organisms, depth found at in soil, 180;
distribution of, in soil, 179;
effect of poisons on, 176;
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