e lose, for the time being,
more or less of it from its becoming locked up in insoluble combinations
in the soil. For spring crops, such as barley or oats, or spring wheat,
or for a meadow or lawn, or for top-dressing winter-wheat in the spring,
the nitrate of soda, provided it is sown early enough, or at any time in
the spring, just previous to a heavy rain, is likely to produce a better
effect than the sulphate of ammonia. But for sowing in the autumn on
winter-wheat the ammonia is to be preferred.

"Saltpetre, or nitrate of potash," said the Deacon, "does not contain as
much nitrogen as nitrate of soda."

"And yet," said the Doctor, "if it could be purchased at the same price,
it would be the cheaper manure. It contains 46-1/2 per cent of potash,
and on soils, or for crops where potash is needed, we may sometimes be
able to purchase saltpetre to advantage."

"If I could come across a lot of damaged saltpetre," said I, "that could
be got for what it is worth as manure, I should like to try it on my
apple trees--one row with nitrate of soda, and one row with nitrate of
potash. When we apply manure to apple trees, the ammonia, phosphoric
acid, and potash, are largely retained in the first few inches of
surface soil, and the deeper roots get hold of only those portions which
leach through the upper layer of earth. Nitric acid, however, is easily
washed down into the subsoil, and would soon reach all the roots of the
trees."

CHAPTER XXXVII.

BONE-DUST AND SUPERPHOSPHATE OF LIME.

Bone-dust is often spoken of as a phosphatic manure, and it has been
supposed that the astonishing effect bone-dust sometimes produces on old
pasture-land, is due to its furnishing phosphoric acid to the soil.

But it must be remembered that bone-dust furnishes nitrogen as well as
phosphoric acid, and we are not warranted in ascribing the good effect
of bones to phosphoric acid alone.

Bones differ considerably in composition. They consist essentially of
gelatine and phosphate of lime. Bones from young animals, and the soft
porous parts of all bones, contain more gelatine than the solid parts,
or the bones from older animals. On the average, 1,000 lbs. of good
commercial bone-dust contains 38 lbs. of nitrogen.

On the old dairy farms of Cheshire, where bone-dust produced such marked
improvement in the quantity and quality of the pastures and meadows, it
was usual to apply from 4,000 to 5,000 lbs. per acre, and often more. In
o