GAS LIME AS A FERTILISER.

Otago Witness, Issue 2983, 17 May 1911, Page 21

GAS LIME AS A FERTILISER.

A NEW THEORY.

"Ploughboy," in the North British Agriculturist, states that there is a great demand for gas lime, wihieh was at one time considered a useless material as a fertiliser. On analysis it is found to contffiin about 15 per cent, of slaked lime and 24per cent, of calcium carbonate, alonjr with numerous other compounds of calcium with sulphur in variable amounts; a email trace of some nitrogenous compound is also frequently present. That the slaked lime and calcium carbonate have some fertilising value, cannot be doubted, but it is also well known on' the other hand: that many of itihe compounds of calcium with sulphur, such as the sulphides and sulphites, are poisonous, and in order ifco render these substances harmless by oxidising them into sulphates it is usually irecomimended that the gas lime should be exposed to the action of the atmosphere foi" some time before it is applied to the land.

The appearance of the orop at different, stages -of growth would lead one to deduce the following conclusions: —(1) That during the early summer months the crop appears to suffer from being unable to obtain some necessary ingredient of plant food, probably nitrogen. (2) That after this period a rather sudden change occurs, wihen the appearance of the crop would seem to indicate that the plants were being l supplied with more nitrogen than they could readily make use of. (3) That this excessive supply of nitrogen is kept u.p is shown by the liability of the crop to become lodged, and also by the slowness of ripening. 'Most fa.rmens disregard the injunction to expose the gpas lime in a heap for some time. Experience has shown that where the two methods have been tried side by sido the fresh gas lime, if anything, has had the greatest effect on the growth of the prop. _ • . The explanation of these results, in which science and practice are apparently

so contradictory, appears to bo that the effect of treating tho soil with certain antiseptics. This research work shows that the effect of treating the soil with volatile antiseptics is to completely alter the bacterial flora, and while it at first stops nitrification by killing most of tho nitrfiyiinj? germs, it gives those which are loft, and also those which may reach the soil, a fresh field to work in, as most of the other bac teria and low forms o{ animal life, which under ordinary conditions compete with tho nitrifying: bacteria, have been killed off. Thus, once the nitrifying! bacteria again becomes established, nitrification proceeds more rapidly than ever. In the application of gas lime it is not a volatile antiseptic which is used, and which gradually disappears from the soil by volatilisation, but it is an antiseptio which gradluially becomes harmless bv oxidation. The same object is served in both cases, but by different reactions.