t then such manures, from their very nature, are little likely to
affect the permanent fertility of the soil.

_Influence of Farmyard Manure on the Soil._

Of manures which have the best effect in improving a soil's permanent
fertility, farmyard manure is undoubtedly the most important. This is
owing partly to the fact that it is applied in such large quantities,
and partly on account of its composition. Liberal manuring with farmyard
manure, systematically carried out, will in time do much to build up a
soil's fertility. But liberal manuring with artificial manures will also
effect the same end. This it does in an indirect manner by means of the
increased crop residues obtained under such treatment. Indeed one of the
speediest methods of bringing a soil into good condition is by heavily
manuring certain green crops, and then ploughing them in.

_Farmyard Manure v. Artificials._

The question how far farmyard manure may be supplanted by artificials is
one often discussed. We have already referred to this question in the
chapter on Farmyard Manure. It is possible that, with our increasing
knowledge of agricultural science, we may in the future be able to
dispense with farmyard manure, and make shift to do with artificials
alone. At present, however, all our experience points to the fact that
the most satisfactory results are obtained from manures by using
artificials in conjunction with farmyard manure. It is better both for
farmyard manure and artificial manures to be applied together,[241] so
that they may mutually act as supplementary the one to the other. While
this is so, there may be circumstances in which it will be best to use
artificials alone. Where, for example, fields, owing to their situation,
are inaccessible, and where the expense of conveying the bulky farmyard
manure would be very considerable, it may be found more economical to
apply the more concentrated artificial manures. With few exceptions,
however, it will be found most desirable to use artificial manures as
supplementary to farmyard manure, and not as substitutes for it.

_Farmyard Manure not favourable to certain Crops._

While the above is true, it may be well to point out one or two facts
regarding the nature of the influence of farmyard manure on certain
crops. For instance, it has long been recognised as inadvisable in
strong rich soils to apply it directly to certain grain crops, such as
barley and wheat, since such a practice is