THE FARM.

Pelorus Guardian and Miners' Advocate., Volume 29, Issue 38, 18 May 1917, Page 7

THE FARM.

LIFE AND NITRIFICATION IN THE SOIL. There are two great processes g- - ing on contioually in the soil which are known to be due to the acticeness of bacteria : (a) The conversion of ammonia and other compoundcontaining nitrogen, derived from decaying organic matter and nitrogenous fertilisers, into nitrates, the only form in which, so far as wc know, plants can utilise the nitrogen : (b) the utilisation of free nitrogen of the atmosphere by leguminous plants. Both these processes are greatly facilitated by the presence in the soil of a sufficiency of lime. The soil is not an inert mass of material containing certain _mineral substances which plants utilise. Besides the numerous insects, worms, etc., it contains myriads of low organisms not visible to the naked eye, but capable of examination by the aid of the microscope.

They are known as bacteria or micro-organisms, and are so minute that a grain of soil may contain many thousands, increasing and propagating under favourable conditions with incuedible rapidity. They exist in the soil chiefly in the upper layer. A pinch of soil may contain from several thousands to several millions ; loamy soils and soils containing much organic (natter contain most sandy soils contain least. Thj number decreases gradually from the surface soil downwards till about 3 feet, where very few or none are tt—sent.

Each different kind of bacterium performs its own useful purpose in Nature, but in the interest of. economical cultivation it would appear that the growth of some of them have to be encouraged and the development of others to be chocked. The subject, however, is not at present clearly understood, and has to bo further investigated ; for us the practical knowledge is that- organic matter, by increasing the supply of humus to the soil, favours the rapid growth of the kind of bacteria that converts organic ammonia into nitrates, suitable for assimilation by the crops. We have, by the ploughing under of green crops, and other suitable means, a sufficient supply of humus.—" Mark Lane Express.”