BACTERIA

Lyttelton Times, Volume CXXIII, Issue 15919, 3 May 1912, Page 8

BACTERIA

" Soils without bacteria arc dead soils, and as such unfit to support profitable crops." Dr J. 0. Lipman, director of the New Jersey Experimental Station and professor of bacteriology and soil fertility, New Jersey Station College, supplies much information to back up this statement. Every farmer, ho aserts, should know something of the food that bacteria must have and of the conditions required for the proper utilisation of this food. To the average man it is evident that a heap of fresh manure will in time become darker in colour, and will shrink in size; that manure, added to the land, "rots" and disappears; that tho bodies of buried animals, or crops of clover, vetch or rye, ploughed into the soil, v-ainsh in time and become an indistinguishable part of the soil itself. Yet it is not as evident to him that the disappearance of these substances is the result of vital activities. He fails to realiso that the universal process of decay may be stopped by preventing the growth of bacteria as is actually done iu canning factories. In these the food is heated to destroy the bacteria, and is then sealed to prevent the entrance of living germs. It is for this reason that a can of tomatoes, properly stertilised and sealed, ' will keep indefinitely, whereas tho same tomatoes, after the can is opened, will ferment and spoil within one or two days. To tho average man it is uot evident that the process of fermentation is never suspended in the soil, except when the latter is frozen. He often fails to realise that abundant, but not excessive, moisture, a favourable temperature, and a plentiful supply of. air stimulate the activities of soil bacteria. Neither does.ho realise that a soil may contain a relatively large amount of partly decomposed vegetablo and animal matter (humus), and yet may fail, to offer enough food for. the vigorous growth of useful _ bacteria. Let it bo remembered in this connection that soils are formed slowly out of weathered rock, that they become gradually richer in available plant food and richer in vegetable matter and bacteria. Tho day comes at last when these virgin soils make the acquaintance of tho farmer and his implements of tillage. And as the furrows are turned, as the soil is' mellowed, and as the air and water and sunshine aro made to minglo with it the bacteria are stirred to feverish activity. They have food a-plenty, and they attack vigorously the plant and animal materials that had been accumulating, perhaps throughout many centuries, as prairio sod auad forest mould. GROWS LESS PRODUCTIVE. But after a time tho lean years come, and the farmer wonders why his land is growing less and less productive. The soil that was once dark in colour, and mellow to the touch, as if instinct with life; has become lighter in colour and lifeless to the touch. Why this change, and what of tho bacteria that were so generously fed in the newlyestablished fields? An answer to these questions may be found in tho history of every agricultural country. It is the story of young soils in their decline. It is the story of vegetable matter decaying rapidly at first, and then, more and more slowly, until the residues finally become so inert, so resistant to decay, that tho bacteria fail to secure enough food, and come upon a period of starvation. For, after all, it is not so much tho quantity of humus in the soil, but the quality of it. that reguJates the growth and activity of bacteria. It is surprising what enormous quantities of plant food aro present in manv so-called "run-down" or "wornout" soils. Yet, notwithstanding tho abundance of plant food, tho crops do not yield profitable returns. There is not enough fermentation in theso soils, the perfect bacterial machinery is lacking, and tho acids and other chemical products of fermentation are not abundant enough to provide for a rapid breaking down of the rock particles, and tho formation of available phosphorio acid and potash. But these " worn-out" soils receive more or less regular applications of fresh manure, or of green clover, cow peas or vetch, and the bacteria will find again enough digestible food in them, and'the abundant, harvests will come back slowly but surely. In this wise many of the abandoned farms in the east have returned to their old prosperity, just as the soils of Europe (after a period of decline) have readied a stage of intensive cultivation.

SOIL FERMENTATION. In considering the quality of hunvus serving as food for bacteria, it should be remembered that it should contain a sufficient proportion of nitrogen, and should not be too acid. Everything being equal, the greater the proportion of nitrogen in fresh vegetable and animal matter the more readuy it will be attacked by bacteria. For tins reason horse manure will ferment more rapidly than cow manure, and clover, rape, Vetch, peas, etc., will ferment more readily than rye, maize or wheat. The legumes are, therefore, soil enriching crops, not merely because they add nitrogen to the land, but because they are an acceptable food to decay bacteria, and ferment m a more intensive manner than rye or wheat. AS fermentation proceeds, .various acids are formed, and these may accumulate to a sufficient extent to hinder the further growth of the bacteria. Hence an abundance of lime is essential for keeping the soil sweet, and the activities at their maximum, nrft* more, bacteria are, after all, minute plants, and. like higher available phosphoric acid . and othei mineral suWnce for their vigorous growth. On account of this fact the fseo commercial fertil.sors (together with the green manures above) will provide ior more rapid of the land. «£ MiT activity ni e t,e soiT Soils 'whose bacteria are veil fed wl also support crops that are wp 11 fed But since it. is, not possible * i « ,«»11-fed bacteria in soils poor to have we thnt in tllP f ong 1,1 ' Cnmercial fertilisers alone are' JT Sent or maintaining soils pern, Sv Fertile, and that permanent ferS can be assured only when oommerical fertilisers are supplemented "ther by animal manures or by green manures. ________———