Boys' Second Book of Inventions

by Ray Stannard Baker

Now, the trouble, the great problem, lies right here: in the difficulty of obtaining a sufficient amount of fertiliser—in other words, in getting food enough to keep the soil from nitrogen starvation. Already we ship guano—the droppings of sea-birds—from South America and the far islands of the sea to put on our lands, and we mine nitrates (which contain nitrogen) at large expense and in great quantities for the same purpose. And while we go to such lengths to get nitrogen we are wasting it every year in enormous quantities. Gunpowder and explosives are most made up of nitrogen—saltpetre and nitro-glycerin—so that every war wastes vast quantities of this precious substance. Every discharge of a 13-inch gun liberates enough nitrogen to raise many bushels of wheat. Thus we see another reason for the disarmament of the nations.

A prediction has been made that barely thirty years hence the wheat required to feed the world will be 3,260,000,000 bushels annually, and that to raise this about 12,000,000 tons of nitrate of soda yearly for the area under cultivation will be needed over and above the 1,250,000 tons now used by mankind. But the nitrates now in sight and available are estimated good for only another fifty years, even at the present low rate of consumption. Hence, even if famine does not immediately impend, the food problem is far more serious than is generally supposed.

Now nitrogen, it will be seen, is one of the most precious and necessary of all substances to human life, and it is one of the most common. If the world ever starves for the lack of nitrogen it will starve in a very world of nitrogen. For there is not one of the elements more common than nitrogen, not one present around us in larger quantities. Four-fifths of every breath of air we breathe is pure nitrogen—four-fifths of all the earth's atmosphere is nitrogen.

But, unfortunately, most plants are unable to take up nitrogen in its gaseous form as it appears in the air. It must be combined with hydrogen in the form of ammonia or in some nitrate. Ammonia and the nitrates are, therefore, the basis of all fertilisers.

Now, the problem for the scientist and inventor takes this form: Here is the vast store-house of life-giving nitrogen in the air; how can it be caught, fixed, reduced to the purpose of men, spread on the hungry wheat-fields? The problem, therefore, is that of "fixing" the nitrogen, taking the gas out of the air and reducing it to a form in which it can be handled and used.

Two principal methods for doing this have already been devised, both of which are of fascinating interest. One of these ways, that of a clever American inventor, is purely a machinery process, the utilisation of power by means of which the nitrogen is literally sucked out of the air and combined with soda so that it produces nitrate of soda, a high-class fertiliser. The water power of Niagara Falls is used to do this work—it seems odd enough that Niagara should be used for food production!

The other method, that of a hard-working German professor, is the cunning utilisation of one of nature's marvellous processes of taking the nitrogen from the air and depositing it in the soil—for nature has its own beautiful way of doing it. I will describe the second method first because it will help to clear up the whole subject and lead up to the work of the American inventor and his extraordinary machinery.

Nearly every farmer, without knowing it, employs nature's method of fixing nitrogen every year. It is a simple process which he has learned from experience. He knows that when land is worn out by overcropping with wheat or other products which draw heavily on the earth's nitrogen supply certain crops will still grow luxuriantly upon the worn-out land, and that if these crops are left and ploughed in, the fertility of the soil will be restored, and it will again produce large yields of wheat and other nitrogen-demanding plants. These restorative crops are clover, lupin, and other leguminous plants, including beans and peas. Every one who is at all familiar with farming operations has heard of seeding down an old field to clover and then ploughing in the crop, usually in the second year.

The great importance of this bit of the wisdom of experience was not appreciated by science for many years. Then several German experimenters began to ask why clover and lupin and beans should flourish on worn-out land when other crops failed. All of these plants are especially rich in nitrogen, and yet they grew well on soil which had been robbed of its nitrogen. Why was this so?

It was a hard problem to solve, but science was undaunted. Botanists had already discovered that the roots of the leguminous plants—that is, clover, lupin, beans, peas, and so on—were usually covered with small round swellings, or tumors, to which were given the name nodules. The exact purpose of these swellings being unknown, they were set down as a condition, possibly, of disease, and no further attention was paid to them until Professor Hellriegel, of Burnburg, in Anhalt, Germany, took up the work. After much experimenting, he made the important discovery that lupins which had nodules would grow in soil devoid of nitrogen, and that lupins which had no nodules would not grow in the same soil. It was plain, therefore, that the nodules must play an important, though mysterious, part in enabling the plant to utilise the free nitrogen of the air. That was early in the '80s. His discovery at once started other investigators to work, and it was not long before the announcement came—and it came, curiously enough, at a time when Dr. Koch was making his greatest contributions to the world's knowledge of the germ theory of disease—that these nodules were the result of minute bacteria found in the soil. Professor Beyerinck, of Münster, gave the bacteria the name Radiocola.