nitrate of soda, will produce the same effect, although
the conditions necessary for its successful action may not be the same
with the two manures. It is alleged that nitrate of soda is
advantageously conjoined with common salt, which is said to check its
tendency to make the grain crops run to straw, and to prevent their
lodging, as they are apt to do, when it is employed alone. But
considerable difference of opinion exists in this point, many farmers
believing that salt produces no effect. When employed for hay,
especially when mixed with clover, it is advisable to use it along with
an equal quantity of sulphate of ammonia, which gives a better result
than either separately.

_Salts of Potash and Soda._--The substances just mentioned must be
considered to owe their chief manurial value to nitric acid; but other
salts have been used as manures in which the effect is undoubtedly due
to the alkalies themselves. With the exception of common salt, most of
the alkaline salts have only been used to a limited extent; and it is
remarkable that, so far as our present experience goes, there is no
class of substances from which more uncertain results are obtained.

_Muriate and Sulphate of Potash_ have both been used, and the former
has in some cases, and in particular seasons, produced a very remarkable
effect in the potato; but in other instances it has proved quite
useless. The cause of this difference has not been ascertained. Sulphate
of soda has also been used to some extent, but apparently without much
benefit; and there is no reason to expect that it should act better than
common salt, which can be obtained at a much lower price.

_Chloride of Sodium, or Common Salt_, has at different times been
employed as a manure, but its effects are so variable and uncertain,
that its use, in place of increasing, has of late years rather
diminished, it having frequently been found that on soils in all
respects similar, or even on the same soil, in different years, it
sometimes proves advantageous, at others positively injurious. Its use
as an addition to nitrate of soda has been already alluded to, and it is
said that it produces the same effect when mixed with guano and salts of
ammonia. The accuracy of this statement is doubted by many persons, and
the explanation which has been given of the cause of its action is more
than dubious. It is supposed to enable the plant to absorb more silica
from the soil; but this is a speculative