NITROGEN-GATHERING BACTERIA.

New Zealand Herald, Volume XLII, Issue 13011, 31 October 1905, Page 7

NITROGEN-GATHERING BACTERIA.

PROFESSOR THOMAS' EXPERIMENTS. WONDERFUL RESULTS. . [Bt OVK AGRICULTURAL REPOBTEU.} ' Thk subject of utilising nitrogen-gathering bacteria for the improvement of soil fertility has received a considerable amount of attention in New Zealand recently. A good many of our advanced farmers have commenced experimenting with it since the cultures were made available, commercially, and the Agricultural Department has undertaken a series of tests at the various experimental farms. No one, however, in New Zealand has gone into the. question so thoroughly or so scientifically as Professor Thomas, of tho Auckland University College. Several mouths ago ho delivered an address on nitrogen-gathering bacteria at the New Zealand Institute, and afterwards by special request supplied a highly instructive article on this subject for these pages. The professor is an exceedingly busy man, and his college duties absorb much of his time and energy. In spite of this he has been able to devote some of his rare leisure to tho ex-, animation of nitrogen-gathering bacteria in his own 'laboratory and to practical experiments with it in his own garden. I had tho opportunity quite ■ recently of chatting with the professor on this subject, and for my benefit he went through the process of preparing cultures cf the. nitrogen-gathering bacteria. First he dug up a well-grown pea plant from his kitchen garden. On this plant, as on nearly all leguminous plants, were various-sized nodules. These nodules contain the nitrogen-gathering bacteria, to which the name Pseudomonas radicicola has been given. It is by the aid of these bacteria that leguminous plants have the power to assimilate tho free nitrogen of the atmosphere, and not only to use it for their own benefit in building up their own structures, and in providing these plants with the constituents that render them so highly valuable for stock, but actually to gather up a quantity of this very expensive substance for storage in the soil. The nodules which the professor took off the roots of the pea plant were only about half the size of a small grain of wheat, and the bulk of their size consisted of an "outer covering. Inside were the busy bacteria, so minute as to be only separately visible under a powerful microscope. The nodules had to be carefully washed in a powerful antiseptic to prevent the possibility of other kinds of bacteria intruding; then the professor carefully cut off the outer covering of the nodule and extracted a tiny brown fragment representing a mass of bacteria. There was no time, of course, to follow the experiment through its various phases, but if this tiny fragment were placed in a proper medium the bacteria would develop rapidly. Then would come the work of training these bacteria to their real usefulness. Scientists have found that by placing them in a proper medium their nitro-gen-gathering powers can be increased tenfold, and that they can be so manipulated as to be made available for practical use, or for distribution at a distance. The medium used by .Professor Thomas consists of 100 parts cane sugar, three parts phosphate of potash, 10 parts of sulphate of magnesium in 10,000 parts of distilled water. When the bacteria have developed in this solution they show as a whitish colouring in the water, not unlike milk in suspension, Heeds of legumes sprinkled with the liquid will take to themselves colonies of bacteria, and if the soil is suitable they/ will colonise the rootlets of the plant grown from the seed, and will form on them nodules each containing myriads of bacteria which will spend their time gathering nitrogen for the supply of the plant. It should be recognised that each different variety of legume produces a different quality of bacteria, and farmers who' use clover-raised bacteria for peas or any other plant will meet with disappointment. Professor Thomas told mo that the character of the bacteria can be much improved by selection as well as by cultivation. By taking the finest nodules from the finest plants the most vigorous bacteria can b% obtained. .'. ' Strangely enough the absence of nitrogen in the soil aids the bacteria in their work. Where nitrogen is present in sufficient quantities there is no work for them to do, and they become useless. The same thing applies if the bacteria are cultivated in a j medium rich in nitrogen.- •-? ~* •. "> •"'• ! The professor showed me clover and mus- i tard growing as pot plants: one inoculated ' with cultivated nitrogen-gathering bacteria, another grown with the ordinary amount of nitrogen, and another grown without nitrogen. These plants were growing in sterilised white sand, ( utterly deficient in fertility itself, but to which phosphoric acid and potash had been supplied. The idea that these bacteria will make leguminous plants grow luxuriantly in soils deficient in every form of fertility is common enough among people who know but little about the subject; but they are only capable of supplying nitrogen, which, after all, is the element most needed in even socalled poor soils, and the most expensive to supply as a manure. The clover grown by the professor after being inoculated with nitrogen-gathering bacteria was so superior in every respect to the clover grown even in soil supplied with nitrogenous manure, and so far beyond that grown in soil containing neither nitrogen nor bacteria, that no farmer could fail to bo impressed with .the possibilities' of seed inoculation, and it is quite certain that if some of the experiments now being tried by farmers fail, it will not be the fault of the nitrogen-gathering bacteria, but the fault of its wrong application. One striking feature in the professor's experiments was not only the poorer growth of seeds planted in soil deficient in nitrogen, but the large actual loss by starvation. Fifty per cent, of tho mustard ; seed grown without nitrogen had succumbed , and the surviving plants, poor si they were, owed some of their vigour fa» being able to feed on the remains of their defunct brethren. The practical value of nitrogen-gathering bacteria lies in the fact that they supply nitrogen, which is the most necessary of all constituents to soil fertility, and the most expensive to supply as an artificial manure. Most soils possets a sufficiency of potash and phosphoric acid. Even the light soils of the Waikato and Taupo districts and the gum lands of tho North have a fair amount of these elements, their chief lack being nitrogen. The way to utilise, and at the same time to improve these soils is to grow on them leguminous crops such as clovers, trefoils, lupines, vetches from seed inoculated with their special bacteria. These crops, if other conditions are suitable, will not only provide feed for stock, but will gradually improve the character and fertility of the soil itself by adding humus and nitrogen-, the two things which now they most lack. As so many misconceptions exist regarding the use of nitrogen-gathering bacteria, the following information supplied by the United States Department of Agriculture on the question of inoculation is given :— Inoculation Is neresnary— I. On a soil low in orfjjnio mutter that to not previously borne leguminous crops. 2. Tf tlie legumes-previously grown op. the same land yere ileroi'l of nodules, or " nitrogen knots," thus showing the need for the noduleforming bacteria. 3. V?hen the legume to be sown belongs to a speeie3 not closely related to one previously grown on the -amii soil. For instance, sail in which red clover forms nodules will often fail to produce nodules on lucerne when sown with the latter crop tor the first time. Inoculation will prove advantageous—l. When the soil produce* a sickly grow* of legumes, even though their roots show some nodules. If the cultures introduced sire of the highest virility, their use will often result Is * more vigorous growth. 2. When a leguminous crop already sown has made a stand, but shows signs of failing, owing to the absence of root nodules, the use of the culture liquid as a spray or try mixture with soil' or top-. dressing may save the stand If other" conditions ure favourable. On the other hind, Inoculation la unnecessary ami. oilers little prospect of gain: 1. Where the leguminous crops usually grown are producing up to the average, and the roots show nodules In norms! abundance, cultures of nitrogen-fixing bacterid are not to be regarded in the Ught of fertilisers, or m capable of increasing the yield under average conditions. They do not contain nitrogen Itself, but bacteria, which, make it possible for the legume* to secure nitrogen from the air (through the formation of root nodules). Where the soil is already adequately supplied with these bacteria, it will not usually pay to practice artificial inoculation. 3. When the soil is already rich in nitrogen, it is neither necessary nor profitable to inoculate a soil, rich in nitrogen when sowing legumes. Not only does the available nitrogen in the soil render tho formation of nodules loss necessary, but the nitrogenous materials in the soil largely prevent the bacteria from forming nodules. Any'increased virility in nitrogen-lijiing power possessed by any of the types of bacteria yet distributed may be, rapidly lost in a soil containing an abundance of nitrogen, Because the bacteria are in a medium in which there is no demand for activity in securing atmospheric nitrogen. .';-.-. Inoculation will fail where other conditions (aside from the need of bacteria) are not taken into account, among which are the following:—l. In soil that Is acid ami In need of lime, liming to correct acidity is m important for the proper activity of the bacteria as for the growth of the plants. ".'ln soil th.it is deficient in fertilisers, such as potash, phosphoric acid, or lime, the activity of the bacteria in securing nitrogen from the air and. rendering it available to the legumes does not do away with the need for such fertilising elements as potash and phosphorus. 3. It must also be remembered tli.it inoculation does not " act like magic;" it will not overcome results doe to bad seed,' improper preparation and cultivation of the ground, and decidedly adverse conditions of ireatliet or climate. In the use of, the cultures, also, failure is almost certain whero the directions are not carefully atudisd »ad intelligently followed.