GERM LIFE IN THE SOIL.

Otago Witness, Issue 2287, 30 December 1897, Page 5

GERM LIFE IN THE SOIL.

By Fobbes Bujmt, F.H.A.S

Scientist* are etill on the threshold of their knowledge in regard to germ life in relation to agriculture, yet much has been gathered regardng the nature and condition of bacteria in the soil. The study of bacteriology ia an absolute necessity to those who desire to understand the scientific principles of agriculture. Every year fresh evidence is cropping up to show what an important part the microbe plays in agricultural economy. Science shows that microbes are as necessary to the farmer as bis stock. Late discoveries prove that the presence of the microbe fc required ia the soil to prepare food for plants.

Jn dairying b.scteria play an iniportaii'. part ; tho ripeaing of cream fit to churn, the colour bi the batter,' aud the tasle are all due .to theie presence. Many speak of germs as',minuta forms of animal life, while' in reality they belong to the Vegetable kingdom. A Their minuteness is most etrikiug'; oiaDy are nob more thau one-twenby-tHth thousand part of an iuch iv thickness. Tuo most powerful microscope is required to reveal their presence, and it is only when they are packed together ia myriads that they are apparent to the naked eye, Ths bacteria roproduca themselves in different ways —by the bacterium splitting itself in two, each hilf forming anew microbo, or by throwing off small buds. A third mode of development U carried out by means of Bpores or seeds. The most important; conditions for the-developmenb of microbes are food, moisture, and heat. Ninety degrees Fahr. are raoat favourable, whili a temperature of 50d"g higher is able to destroy most bacteria, One of the raosb astounding chsracteriatiog of these miuuts organisms is tha rapidity, at which they are able to increase. Calculations show that they are able to reproduce bheaaaelves within an hour's time. Sunlight has a destructive effecb on germs,' and luakily many diseass germ* are killed by this sueiantf.

Garna life in the soil is more particularly interesli"g4io thosa engaged in agricultural parsuifes. Formerly we looked upon the soil as de&d, iuert; matter, while ib really teems with micro-organic life. A hundred million or more may be present in a single ounce ef soil, and for the mostpaitarobusy carrying out minube tillage operations, which result ia the preparation of food substances that can be assimilated by ihe roots of plants. Until quita recently ib was believed fchab all microbes req^irad organic aiaSler foe thoir development, bub discoveries prove thai a certain cl«t&s that aro active in the iraportaut process known as nitrifictitio'h cau clevalop on bare rock aurfaca. They form the first- lavsr of orgaui^ mibter and pave the way for a high-jr .vegetable gcowtb. Tnu3 oao class of microbes initiate the 'primary stage, whijle another ekss carry iv on. Orgauisms ate chiefly found in the superficial layers of tho coil, and experiments prove that they are not to bo met with 61'fc below the surface, and that they are not sclkc at mote than a depth of 10iu. Their numbers vary according to the season of the year, and in the summer months they are most abundant One class oxidea the ingredients o£ this soil, while ar-iother acts in au exactly opposite dirfe'ion. A fcbird eUas dbrive niirogea from iho air, which they fix>and convert into form-i available for plaut requirements. Nitrogen ia the mjsfc important of allpl%nt food, and the discovery of the na'.ure of the process ol nitrification must be regarded as one of the mosfc important inado in connection with the sciancs of agriculture. Nitrogen occurs in the soil in forms of organic compounds, as ammonia saltSi as uitrilen, and as nitrates. Ths process of nitrification take 3 plaoe in throe stages in which three dijjerrint classes o£ organisms Are engaged. Since "tire fertility of a soil- may bo taid to depend, io no hmall extent on the abundance of tho nitrifying organisms, the highly practical question arises, Is it feasible to seed a soil wibb. these valuable, orgaaisma ? An answer m the iffionaliva cau be given, as numerous orperiaients have proven that bentfioial results may be obtained by inoculating sterile fields with a substance rich in nitriiyiug bacteria. The name nitraqtn (pronounced jeVtrag-eaD) has been invented to describe a jelly (gelatine) on whica tb-ere has been sown minute organisms •derived from tho little warty growths or nodules lhat are found on the roots o? leguminous pUnls— ie., bears?, peas, vetches, clover, &c. Ibis substance is manufactured by a ficni ot German chemists and sold in small bottles coßtamrngjan ounce or two of the jelly, on whose surface » whits mouldy-looking stuff has been grown. 16 w claimed th*t if this fuugua is mixed with abtrab half a gallon of water* and the water sprinkled ciref.Uly over lowb of earth .and mixed thoroughly ib is capable of inoculating halt an acre of land when sown as a top-dreas-ng, and that the land wM produce a much larger stop th»n uninoculated land. The existence oE nodules or fleshy excresences on the r,00t3 ot leguminous plants has been known for a leng time, but ib was only in 1836 that it was discovered that-.the tissues oE these nodules were filled with bacteria. The nodules are found, on analysis to be very rich iv nitrogen, and as they grow old they soften and disintegrate and give back some of their living nitrogenous constituents to the soil in the form of spores.' Glover b3ing a member of the lpgumiu^ua order it can be easily understood that after a good crop of clover come 3 a good crop of wheat, for wheat, like other cerealsj depends on its vigorous growth upon finding in the soil au immediate supply oc veiy easily assimilable nitrogenous matter. R-ifereuce may bo mads to the fact that the soil cantaius disease-producing germs. By the burial of animals which have died of germ-

produced disease the further propagation of the disease has known to result It ia well worthy of notice that it would pay farmers to burn carcases of dead sheep or cattle iusttad of burying them, or, as is more commonly the case, leaving them uuburied.