A MANURING PROBLEM

Otago Daily Times, Issue 21538, 9 January 1932, Page 3

A MANURING PROBLEM

. In working out any system of manuring, whether for the garden or the orchard, probably the most common of all mistakes is ,to overlook the after-effects of the various manures and fertilisers used. Practically all manures have this twofold action—-their immediate effects and their after-effects, and the second are often of even greater importance than the first. In this, respect the diet of plants is very similar to our own. No single article of food is completely absorbed, and it, therefore, follows that, whatever manure you may apply, there will of necessity be certain residues left behind in the soil as a whole, and especially what is their effect upon the crop that is to follow? The foregoing are questions which urgently need an answer if one is to get the best value out of the manures used.

The, great fact to remember here about artificial manures is that quite a large number of them,, although not really acid in themselves, develop very considerable acidity during their decomposition in the soil. Sulphate of ammonia and common superphosphate are cases in point, and where they have been used at all liberally, their acid residues can be distinctly traced, not only in the unhealthy condition of the new crop, but actually by chemical means. , The simplest remedy against this is to give a light dressing of quicklime, which neutralises the acidity in a very short time, and allows full advantage to be taken of any food materials still available.

It must not be assumed that the same results would, be secured by adding lime to the fertilisers, or by applying both simultaneously. Neither is it to be interpreted that because superphosphateand sulphate of ammonia produce acidity, they are condemned as fertilisers. Trie real point which is here, stressed is that after-effects must not be ignored, and that steps must be promptly taken to counteract effects of excess when they become evident.

One of the first principles of all manuring should be that the residues of any fertiliser must be appropriate to the following crop. So, if heavy dressings of nitrogenous manures have been given to, a bed of cabbages, and we follow these with peas one is likely to get an abundance of haulm,,but a very poor yield, The remedy in this case is not to give a general manure for the peas, but a purely phosphatic one, such as some preparation of bones. In this way the balance in the soil is restored. The peas seize readily on the phosphates, and the nitrogenous residues from the brassicas, being now in their due proportion for the new crop, are rendered powerless to do harm. The after-effects of the natural organic manures are of a different character altogether. These consist very largely of humus, and their continued use tends always to raise the humus-content of the soil. Their chemical manurial effects pass away more or less quickly, but the organic residues remain for prolonged periods, and play a very valuable part in the production of succeeding crops. Even natural manure, if used liberally and persistently for a number of years, will result in soil sickness through producing an excess of humus. It may be protested that too much manure is unprocurable in these days, but in some country villages this is not so, Lime, again, is the best corrective, and rough digtring before >frost is also helpful.—Royal Scot, in Amateur Gardening.