d never be applied to the potato crop in the form of
chloride.

In the late Dr Voelcker's opinion, the conditions under which salt had
the most favourable action on the mangel crop was in the case of a light
sandy soil, and applied at the rate of 4 to 5 cwt. per acre. Its action
when applied to clay soils was not so favourable.

_Rate of Application._

Lastly, the rate at which it may be applied will naturally vary. From 1
cwt. and even less, up to 6 cwt. or even more, has been the rate at
which it has been commonly applied in the past. From what has been said,
it will be seen that it is more likely to exert a favourable influence
when applied only in small quantities.

CHAPTER XXII.

THE APPLICATION OF MANURES.

The conditions which regulate the application of manures are many and
varied, and the subject, it must be admitted, despite the large amount
of investigation already carried out, is most imperfectly understood.
For these reasons it is impossible to do little more than lay down
certain general principles which may be of service to the agriculturist
in guiding him in carrying out the manuring of his crops.

_Influence of Manures in increasing Soil-fertility._

In the first place it may be asked, How far can what we may call the
permanent fertility of a field be influenced by the application of
manures? And to this question the answer must be made, that the
influence of manuring in increasing soil-fertility is very slight and
only very gradually felt. This is illustrated by the difficulty
experienced in attempting to restore to a fertile condition a soil which
has long been treated by an exhaustive system of cultivation. In such a
case it will be found impossible to restore the fertility of the soil,
except very gradually. Farmers who farm in new countries, and in rich
virgin soils, little realise sometimes how quickly they may impoverish
the fertility of their soils by exhaustive treatment, and how slow the
process of restoration is. Nor is this strange when we reflect on the
relatively small quantities of fertilising ingredients we are in the
habit of adding to the soil by the application of manures, and the
nature of their action. The small rate at which they are applied, and
the impossibility of distributing them equally in the soil, explain how
comparatively limited their action must necessarily be. Some manures, it
is true--viz., those which are soluble--are more equally distributed;
bu