Potash.—For a long time the United States had more difficulty in getting potash than phosphorus. The only largely worked deposits were in Stassfurt, Prussia; other sources, such as Alsace and Spain, supplied relatively little. The danger that the supply would be cut off, and the price rise to a prohibitive figure led the United States government to undertake a search for new sources. This led to the use of several salt lakes whence most of the limited American produc tion now comes. It also led to the use of kelp along the Pacific coast, as already described, and to the further development of the processes of extraction of potash from the dust of cement mills and blast furnaces.
The largest single source of potash in the United States is Searles Lake in southwestern California. This strange desert lake, twenty square miles in extent, resembles a mass of ice covered with an inch or two of slush and saturated with bitter brine. The ice-like Material is rock-salt and other saline materials deposited as crystals by the drying up of a large lake whose traces are still seen in numerous shore-lines at high levels. The brine is pumped from wells 75 or 100 feet deep and evaporated until the potash crystallizes out. The product is shipped all over the country to replace that which the farmers have sent to market in the form of meat, wheat, and other food supplies. If the farmer would properly preserve the straw, cornstalks, cotton-seed bulbs and similar substances that are now wasted or burned, the need of potash would be much diminished.
The Search for Nitrogen.—Among the essential ingredients of the soil nitrogen is much the hardest to obtain. Its original source is chiefly the air. The amount in the air is inexhaustible. Yet until recently it was almost useless to the farmer, for no one knew how to convert it into a soluble compound that could be carried through the roots of the plants. This is because nitrogen is one of the most inactive chemical elements. Quite unlike such an active substance as oxygen, it will not readily unite with other elements.
No plants are by themselves able to take nitrogen from the air. Fortunately, however, there are certain bacteria which have this power. They grow only on plants of the legume family, that is, on beans, peas, clover, alfalfa, and similar species. They thrive espe cially on the roots, where they form little bunches or tubercles full of nitrogen. All other cultivated plants diminish the supply of nitrogen in the soil; the legumes alone replace it. Farmers have known for generations that it pays to plant peas or beans and plow them under for fertilizer, but did not know why. Scientific investi gators after much study discovered the reason and found that the bacteria that cause " nitrification " can be raised artificially, and shipped anywhere. When clover seed is inoculated with them the
roots become covered with unusually large tubercles which contain nitrogen, and thus the fields are fertilized.
Many farmers do not want their land to "waste a year," as they say, while a crop of clover refertilizes the soil. They prefer to raise something that pays in money and therefore are glad to buy com mercial nitrogen fertilizers. This has had some interesting results. The Atacama Desert in northern Chile contains by far the largest known deposits of nitrates or compounds of nitrogen. They have been exploited to the value of $50,000,000 each year. The taxes paid by the British companies that work the nitrate fields are the chief sources of the revenue of the Chilean government. Before the value of the nitrogen was known the Atacama Desert was such a barren waste that no one thought much about it, although Chile. Peru, and Bolivia all laid claim to parts of it. When its value began to be appreciated, however, about 1879, the three countries wanted it. This led to a long war in which Chile was the victor.
Another interesting result of the demand for nitrogen fertilizers is seen in Norway. After the value of nitrates was realized people began to search for means of utilizing the unlimited supply of nitrogen in the air. Success was at last obtained by means of strong electric currents which cause the atmospheric nitrogen to unite with lime or other substances. Much power is required for the electric discharges, so that the process is commercially profitable only where power is cheap. The cheapest known source of power is waterfalls, which are especially abundant in rugged Norway. Since raw materials of most kinds are not abundant there and nitrogen is present every where the manufacture of nitrogenous fertilizers has become an im portant industry. In the United States part of the water power of Niagara is being used for the same purpose.
The work of obtaining fertilizers from old bone deposits, from desert lakes, and from the air may seem remote from the lives of people who live in cities. Yet it concerns every one of us. The farmers supply us with most of the materials for the food and clothing which play so large a part in the lives of all of us. If the farmers do not have rich soil and cannot raise their crops abundantly and cheaply, the price of food and clothing goes up, and we all suffer. Therefore, it is of the greatest importance that the farmers' need of good fer tilizers should be fully/net.