AGRICULTURE BELOW GROUND. T HE rapid progress of science is brought
home to the newspaper reader when he is confronted with auk question in which bacteriology plays a part. Practically speaking, it is all a discovery since he was at school. AS a "general reader," he has become aware that to bacteria we owe alike the taste in butter and the will-o'-the-wisp, a very large number of diseases and the purification of sewage; bat much farther forward he walks with hesitation. The Tines certainly did a useful service the other week in printing two or three columns of what would be regarded by scientific men as elementary instruction on the life and work of bacteria. Willy-nilly, the public has to "get up" baeteriology a little.
It cannot escape from bacteria. They are in every pint of London air, they lead a particularly prosperous life in the morning milk, and the most profitable utilisation of the 'toil, in which the nation is so greatly concerned, depends upon treating the bacterial hosts it contains in the most considerabb way. Friends and foes among the bacteria of the air, of food, and of water may be safely left, perhaps, to the dootora.
Those who have the care of our health will, no doubt, be able to see to it that the public gets to know all it ought to know about the micro-organisms which share with it the life above ground. It is necessary, however, that the worker of the soil, and all who are interested in his work at second hand, should have an adequate conception of the infinitesimally small life that flourishes there. The land, in order to bring forth the largest possible increase, must be humoured, and it is certain that it will never be properly humoured until the idea that earth is only dirt is killed for good. Shakespeare's "dead earth" is hopelessly unscie0ific. Instead of being dead, the soil from cultivated farm-land or a garden may yield, even in the small quantity which will lie on & halfpenny, anything up to ten million living things. It is gradually being realised that the science of the cultl.
vation of the land must be largely the science of yoking to the service of man the teeming life of the soil. The farmer makes his butter and cheese by the aid of bacteria. It is necessary that he should also give thought to the bacteria that feed the grass, that feeds the cow, that yields the milk that the bacteria work upon to his advantage in his dairy.
Of all the things that the farmer needs to make the various plants he grows flourish, none is more expensive than nitrogen: The dung-cart cannot travel all over his fields, and Its contents may not contain more than ten per cent. of nitrogen, In many cases agriculturists have been in the habit of stip- plementing the stockyard supply with "London manure."
But motor-cabs, motor-'buses, and motor-lorries are rapidly diminishing the supply. All the steam, petrol, and gas enginet that are introduced on the farms further reduce the quantity available for the land. Sewage, which might be a great source of nitrogen supply, is poured wastefully into the sea: A few years ago Sir William Crookes, observing 'how the world's stock of guano had been lessened, and that the end of its nitrate supply would soon be within sight, warned a rapidly multiplying world that it might be faded by the problem of a nitrate famine. There was only one way to avoid that famine,—nitrogen must be got from the air. There are thirty-five thousand tons of it in the air above every acre of the land that is crying out for it. Unfortunately nitrogen is the shyest of elements ; it is difficult to persuade it to comi3 into chemical combinations. But electricity has a way of its own with it, and in Scandinavia and alongside Niagara Valle, and in other parts of the world, enterprising companies are producing from cheap water-power electricity which produces in its turn, by the oxidisation of the nitrogen of ‘the air, a.
lime nitrate which contains about thirteen per cent. of nitrogen. Nitrate of soda yields about fifteen and a half per cent of nitrogen; sulphate of ammonia is of about equal utility; but the price of these two products has been rising. If the lime nitrate can be produced a little more cheaply than
is now the case—it is said that there are already facilities for manufacturing forty-eight thousand tons a year—it must come into pretty general use. At any rate, the assault upon the air lies demonstrated that all fears of a nitrate famine may dismissed. •
But how about our bacteria ? We are taught that plants, with the excep Lion of legumes, cannot obtain their nitrogen from the air. But they had to live on the earth long before farmers and gardeners appeared upon it, much lees savants and engineers, . who, with their artificial lightnings, have shown the way to draw out of the air a part of its four-fifths of nitrogen. The plants , were provided for by bacteria. When the farmer applies nitrate to the roots of his plants, he gives them some- thing that they can soak up into their being right away by means of the moisture in the soil. When he provides them with dung or ground bones, or when be inters a dead dog or cow in his orchard, be provides nothing that his plants or trees can feed on at once. , The substances placed in the soil .have to become ammonia, then nitrite, then nitrate, before the plants can fall to upon it. This work is done by different varieties of micro-organisms. It is obvious that this bacterial life may be working in favourable or in unfavourable con- :ditio,ns.. Therefore, when so much depends upon its efficiency, the cultivator of the land must consider what he can do to help. There remain the legumes, which, as has been mentioned, have the power of taking their nitrogen from the !air. They have this power through the well-known nodules or tubercles on their roots. Most residents in the country and amateur gardeners have seen these nodules when the roots of lucerne, clover,, peas, or beans have been turned up. On a six- weeks-old plant they may be about the size of pin-heads, but they may , grow to be almost the size of horse-beans. On lupins they may be as big as small apples. These excrescences are the work of nitrogen-fixing bacteria 'which, live in symbiosis with the legumes,—that is, in the lowliest form of agricultural co-operation. The plants provide the bacteria with the sugar, which, as non-chlorophyll-con- taining organisms, they are unable to take from the air. The ,bacteria pay back with their nitrogenous substance, the material for which is ''drawn from the nitrogen of the air through the air spaces of the plant tissues. When the plant dies and the supply of sugar is cut off, the bacteria enter upon ,a resting-stage, to wait until next year, perhaps, when another plant may offer facilities for a fresh partnership. The hundreds of thousands of pounds which the nitrogen-fixing bacteria add to the wealth of the world may be realised from the fact that there is more than two and a half times as much nitrogen per cent. in lupin seeds as there is in wheat grains. There is also to be reckoned the nitrogen value of the haulms and roots as well. From time immemorial (Virgil, "Georgics," I., 73, 76) farmers have known by experience that corn benefited enormously from a preceding crop of beans. The science of green manuring, which has seen such develop- ments in our time, is, in so far as it is a ploughing in of leguminous plants, an illustration of the marvellously cheap way in which stocks of nitrogen can be given to the soil. ,The fact that during a five years' period American agri- culture has thought it necessary to spend something like .£250,000,000,000 on artificial fertilisers shows how valuable a thing this bacteria-produced nitrogen is to the farmer. Of course there is an immense supply of unavailable nitrogen in the may be more than two thousand pounds per acre in fig, top spit. It is contained in things ,which have not yet given up their nitrogen. By the best methods of working the soil the maximum quantity of .nitrogen is made available.
, Professor Bottomley, of King's College, is the last among a number of scientific men to devise a method of preparing nitrogen-fixing bacteria in the laboratory in a way suitable for application to leguminous crops. As to the results of the application of his and other men's cultures, there are the most conflieting reports. From various parts of the country, from Canada, and from America (see, for instance, a_ Bulletin of the
.Washington Department of Agriculture) come tables showing a large proportion of success in the ease of clover, pea,
bean, or vetch crops. On the other hand, there is the director of Rotharasted writing,that, except in the .peorest soil,,the results are negligible, or, if not negligible, not more than a fifteen-per-cent.. matter. Mr. Chittenden, in his turn, has conducted a series of experiments in the garden of the
Royal Horticultural Society which leads him to assert that "nitro-bacterine" is likely to be of no advantage in the case of garden crops. As to what the opinion of the layman should be in such a situation we bare little doubt. It is, surely, that when the results of many conscientious workers are so conflicting—all Mr. Chittenden's Bete of statistics do not seem reconcilable the one with the other— when some farmers appear to obtain success and some de not, when others have good results with one kind of crop and fail with another, the wise course is to increase the number of experiments. There is as yet, seemingly, no positive conclu- sion to be drawn as to whether or not the laboratory can introduce better bacteria into good soil than exist there already. if—there is a great deal in that " if "—the soil is ,fairly treated. There is ample evidence, however, to justify continued experiment by practical men. Our knowledge of the life of the soil, and the relations of plants to that life, is as yet extraordinarily limited, and it is unscientific to be led into conclusions based on what we are by no means certain are the facts. We are all for a scientific. attitude, but there is a place in scientific inquiry for imagination and hope as well as for accountancy. When we remember that the history of science is, in part, a story of recanting what Lad formerly been believed and accepting what had sometimes been made light of, Experiment, experiment, experiment, and the open mind seem to be the right watchwords in the study of practical soil bacteriology. Readers who may care to look into the subject further will find some interesting micro-photographs in the World's Work for February.
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