Manures and the principles of manuring

by Charles Morton Aikman

Method of Application.

While opinions, therefore, will naturally differ as to the crops to which nitrate of soda will be most profitably applied, little difference of opinion exists as to the method of its application. The inability of the soil-particles to retain it, the frequency of rain, the costly nature of the manure itself, and its immediate availability as a plant-food, all point to the extreme advisability of using it as a top-dressing. Even when used as a top-dressing, it may be advisable not to apply the entire quantity all at one time. By applying it in instalments, little risk is run that, through inclemency of weather, the manure will be lost. Another point of importance in applying nitrate of soda is to secure uniform distribution. This of course is applicable to all artificial manures, but in a very special degree to nitrate of soda, because of its great value and the comparatively small quantity applied.

As the uniform distribution of one cwt. of any material over an acre of soil is by no means an easy task, the mixing of nitrate of soda with some diluent, such as dry loam, is consequently highly advisable. Common salt is often applied along with nitrate of soda. The indirect value of salt as a manure is considerable, and when applied along with nitrate, ensures its more speedy diffusion in the soil, by increasing the soil's capacity for absorbing moisture from the air.

Must be a Sufficiency of other Fertilising Constituents.

A third point of importance in applying nitrate of soda, is to see that the soil is sufficiently supplied with the other plant-foods—phosphates and potash. This is a sine qua non, if the nitrate is to get a fair chance. If it is desired to apply nitrate of soda along with superphosphate of lime, a word of caution is necessary against making the mixture long before it is used. The reason of this is, that a chemical action is apt to ensue, resulting in the loss of the nitric acid in the nitrate of soda. The nature of the soil is another important consideration to be taken into account. In the case of extremely loose and sandy soils, it is scarcely to be recommended as the most suitable form in which to apply nitrogen. If applied to such soils, especial care ought to be taken to minimise risk of loss. No hard-and-fast rules can be laid down as to the quantity in which it ought to be applied. This must be regulated very much by the crop, the nature of the soil, and the quantity of other manures employed. From 1 to 1-1/4 cwt. may be recommended as a suitable quantity for corn crops which are otherwise liberally manured. On strong clay soils this quantity may be judiciously increased up to 2 cwt. Dr Bernard Dyer, who has experimented largely on its use as a manure for mangolds, is of opinion that an application of from 3 to 4 cwt. an acre is likely to prove thoroughly profitable; and the present writer has found in his experiments with turnips that a top-dressing of 1 cwt. amply repaid itself.

Conclusions drawn.

In conclusion, the nature and characteristics of nitrate of soda as a manure may be briefly summed up as follows:—

1. It is a whitish, crystalline salt, extremely soluble, and is quickly diffused in the soil. It should contain 95 per cent of pure nitrate of soda—i.e., 15-1/2 per cent of nitrogen, equal to about 19 per cent of ammonia.

2. Next to sulphate of ammonia, it is the most concentrated nitrogenous manure; the relative quantities of nitrogen these two manures contain being as three is to four.

3. It contains its nitrogen in the most valuable and readily assimilable form—i.e., as nitric acid, the form into which all other forms of nitrogen have first to be converted before they become available for the plant's uses.