Manures and the principles of manuring

by Charles Morton Aikman

In this case the manure should be applied so as not to impair the quality of the herbage. Slow-acting manures are consequently best, such as basic slag or bones, which have been found to be of special value. On wet or marshy land after draining, lime is perhaps one of the best manures to apply in the first instance. As we have already said, farmyard manure will do more to maintain the quality of pasture than any kind of artificial manure. Mr Cooke is of opinion that no system of manuring yet discovered will both thicken and improve the herbage at all equally in success to the careful and regular feeding upon the grass of cattle or sheep, the animals having a good allowance of decorticated cotton-cake, or even of linseed-cake.

ROOTS.

Of all crops roots may be said to require the most liberal application of manure, and to respond most freely to it. They contain large quantities of the fertilising ingredients—nitrogen, phosphates, and potash—and may be regarded as exceedingly exhaustive crops. This is especially the case with regard to mangels, which make particularly large demands on a soil's fertilising ingredients.

Turnips are characterised by the large amount of sulphur they contain; and, according to some, this explains the beneficial effect which gypsum has when applied to them as a manure. This, however, is more probably to be explained by the indirect action of gypsum in setting free the potash of the soil. The fact that the successful cultivation of root crops depends on the application of large quantities of manure, is recognised in practice, as they receive the most manure of any crop of the rotation. Roots flourish best on a light soil which is neither too wet nor too dry; but with liberal manuring and careful tillage, they may be said to do well on any soil. Mangels are generally more benefited by the application of nitrogenous manures than are turnips or swedes, which, it would seem, have a greater power of absorbing nitrogen from the soil than the first-named crop; but it is a mistake to suppose that any of the root crops are not dependent on a ready supply of nitrogen; and the fact that large crops of turnips can often be grown by the application of superphosphate alone, may be taken as a proof that the soil contains plenty of nitrogen. Mangels are, from their deeper roots, more capable of drawing their supply of phosphoric acid from the soil than turnips. They respond, therefore, as a rule, less freely than turnips or swedes to an application of superphosphate. Generally speaking, we may say that the characteristic manure for turnips is superphosphate, and that for mangels is a nitrogenous manure such as nitrate of soda or sulphate of ammonia.

A special reason for manuring root crops is the fact that they are more liable to disease than other crops; and this is especially the case in the early stages of their growth. One of the great benefits conferred on the turnip crop by an application of superphosphate, is the help it gives the crop to pass safely the critical period of its growth. The superphosphate is best drilled in with the seed, in quantities varying from 3 to 5 cwt. In Scotland, it may be well to point out, the manure applied to this crop is very much in excess of the amount customarily applied in England; for in the former country larger applications of manure may be profitably employed. Roots generally receive a large dressing of farmyard manure. Salt has been found in some districts to have a very good effect on the mangel crop, and potash is often found to amply repay application.

Influence of Manure on Composition.

A most interesting point in connection with the manuring of roots is the effect of manure on their composition. This has been most elaborately investigated at Rothamsted and elsewhere. Thus it has been found that the effect of the application of excessive quantities of nitrogenous manures is to produce too great a development of leaves at the expense of the roots.

Nitrogenous Manures increase Sugar in Roots.

Nitrogenous manures also tend to increase the proportion of sugar and diminish the proportion of nitrogenous matter in roots. This has an important bearing on the treatment of roots which are cultivated for their sugar, such as beets, in the growth of which nitrate of soda is the chief artificial manure applied.[245]

The leaf, it may be pointed out, contains a larger percentage of dry matter, both in swedes and in turnips, than the root.