n soil, 203;
in cow-dung, 226-228;
in cow excrements, 280;
in cow-urine, 230;
in farmyard manure, 260;
in fish-guano, 321;
fixed by soils, 58;
gain of, 208;
in guano, percentage of, 329, 330;
guano a source of, 202;
in hoofs and horns, 426;
in horse-dung, 226-228;
in horse-urine, 230;
importance of, 88;
loss of, artificial sources of, 206
--by drainage, 206
--in farmyard manure, 208
--in milk, 207
--in sewage, 208
--sources of, in agriculture, 205;
in meat-guano, 324;
mineral sources of, 200;
necessary for plant-growth, 55;
occurrence of, in animals, 205
--in nature, 199
--in plants, 204
--in soil, 203;
in oxen excrements, 280;
in pig-dung, 226, 227;
in pig excrements, 281;
in pig-urine, 230;
position of, in agriculture, 199-211;
relative trade values of, in manures, 400;
in rocks, 202, 211;
in sewage-sludge, 441;
in sheep-dung, 226-228;
in sheep excrements, 280;
in sheep-urine, 230;
statement of, in analyses of manures, 541.

Phosphorite, 201, 374.

Phosphorus, in albuminoids, 205;
in animals, 205;
in beans, 205;
in peas, 205;
in plants, 204;
in pig-iron, 401.

Physical properties of soils, 66-87.

Pichard on action of gypsum on nitrification, 173.

Pig-dung, composition of, 226;
in dry state, 227.

Pig excrements, 281;
composition of, 281.

Pig-manure, 250;
amount produced per day, 251;
mineral matter in, 251;
nitrogen in, 251;
poor in nitrogen, 251.

Pig-urine, composition of, 230
--in dry state, 231.

Pigeon-dung, 320, 325;
analysis of, 331.

Pigs, excrements of, 281;
food consumed by, 281.

Pisagua, nitrate-fields at, 340.

Plant, action of light on, 38;
amount of hydrogen in, 40
--nitrogen in, 40
--oxygen in, 40;
ash constituents of, 53-55;
carbon fixed by, 37, 38;
food, absorption of, by, 55;
phosphoric acid in, 204;
potash in, 216;
proximate composition of, 36;
relation of ammonia to, 48-50;
source of hydrogen in, 40
--nitrogen in, 40-52
--oxygen in, 39, 40.

Plant-food, absorption of, 490;
amount of soluble, in soil, 100;
early theories on source of, 4;
retained by soil, 57.

Plant-roots, grow downwards, 84;
nitrification promoted by, 181;
openness required by, 83;
room required by, 85;
soil in rel