most invariably sold off the farm. But, on the other hand, owing to
the comparatively small demands they make on fertilising ingredients,
cereals will continue to grow on poor land for a longer period than most
crops,--a fact of very great importance for mankind.

_Especially benefited by Nitrogenous Manures._

Despite the fact that cereals remove comparatively little nitrogen from
the soil, it is somewhat striking to find that they are chiefly
benefited by the application of nitrogenous manures. This fact may be
explained by the shortness of the period of their growth, and the fact
that they assimilate their nitrogen in spring and early summer, and are
thus unable to utilise to the full the nitrates which accumulate in the
soil during later summer and autumn. As they seem to absorb their
nitrogen almost exclusively in the form of nitrates, they are especially
benefited by the application of nitrate of soda.

_Power of absorbing Silicates._

A characteristic feature in the composition of cereals is the large
amount of silica they contain. In common with the grasses, they seem to
possess a power, not possessed by other crops, of feeding upon
silicates.

The special manure, therefore, required for cereals is a nitrogenous
manure, and that, as a rule, of a speedily available character, such as
nitrate of soda or sulphate of ammonia. Furthermore, certain members of
the group are also specially benefited by phosphatic manures.

We shall now consider individually a few of the more important cereal
crops.

BARLEY.

Of cereal crops barley deserves to be considered first, owing to the
fact that it is, of all grain crops, the most widely distributed. In
England, in amount, it comes next to wheat among cereals. Its habits
have also been studied in a very elaborate and careful manner, and have
been made the subject of many experiments, both in this country and
abroad.

_Period of Growth._

The first point to notice about barley is the fact that its period of
growth is a short one. This has a most important bearing on its
treatment with manure. It may be said to ripen, on an average, in
thirteen or fourteen weeks in this country; although in Norway and
Sweden its period of growth is much less--viz., from six to seven weeks.
Indeed no fewer than three crops have been obtained in one year in
certain districts in these countries, and two crops are common. With
regard to the period of its growth, it differs from whe