Manures and the principles of manuring

by Charles Morton Aikman

In this chapter we shall attempt to summarise briefly the results of experiments on the manuring of some of the commoner crops, and we shall start with the manuring of cereals.

CEREALS.

As we have already pointed out, a certain similarity in the manurial requirements of the different members of this class exists. They are characterised, for one thing, by the comparatively small quantity of nitrogen they remove from the soil—less than either leguminous or root crops. Of this nitrogen the larger proportion—amounting to two-thirds—is contained in the grain, the straw only containing about a quarter of the total amount of nitrogen in the plant. The amount of phosphoric acid they remove from the soil is not much less than that removed by the other two classes of crops; but this, again, is also chiefly in the grain. It is on this account that the cereals may be regarded, in a sense, as exhaustive crops, seeing that the grain is almost 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.