Guano.—This fertilizer has been formed from the excrement and carcasses of sea-fowl The composition of guano depends upon the climate of the region in which it is found. Guano from an arid region contains nitrogen, phosphoric acid and sometimes potash, while that from a region where rains occur contains only phosphoric acid, the nitrogen and potash having been leached out. In a dry guano the nitrogen occurs as uric acid, urates and in small quantities ammonium salts. A damp guano contains. more ammonia. The phosphoric acid is present as calcium phosphate, ammonium phosphate and as phosphates of other alkalies. A portion of the phosphate is readily soluble in water. All of the plant food is thus either directly available or becomes so soon after ad mixture with soil. The composition is ex tremely variable. Guano was formerly a very important fertilizing material but the supply has become so nearly exhausted that it is rela tively unimportant at the present time. South America, South Africa, Australia and certain islands in the Pacific contribute to the supply. Other fertilizers of less value are powder waste, agricultural salt, cotton-hull ashes, coal ashes, seaweed, king-crab, mussel and lobster shells, muck, peat, marl, tobacco stems and stalks, crude fish-scrap, wool and hair waste, sewage, street sweepings, etc.
Catalytic Fertilizers.— The term catalytic fertilizer has been used rather loosely to 'desig nate a class of substances that, when added tb a soil, increase plant growth by apparently ac celerating the processes that normally take place in soils. They do not really function as fertil izers because their value does not lie in the nutrients that they possess. The term cataly sis is employed in a chemical sense to mean a change brought about in a compound by an agent that itself remains stable. When an at tempt is made to study these phenomena in soils, it becomes difficult, owing to the multi plicity of factors and reactions, to determine whether the agent is acting in a purely catalytic manner.
A large number of substances have been found to act as catalytic fertilizers. Among these are various salts of manganese, iron, alum inum, zinc, lead, copper, nickel, cobalt, uranium, boron, cerium, lanthanum, and the like. These substances when used in small quantities stimu late plant growth, but are toxic in large amounts.
Of the various plant stimulants mentioned manganese is the only one that gives promise, at the present time, of usefulness on a commer cial basis. The manganese salts that have been found to be effective as fertilizers are the sul phate, chloride, nitrate, carbonate and dioxide. Of these the first has been most often used, and in quantities up to 50 pounds an acre it has in most cases not been toxic. It is supposed to be most effective on poor soils that are not acid.
Lime.— This substance is not a fertilizer in the same sense as are the materials previously discussed. It is because of its effect on the soil rather than directly on the plant that lime is applied to soils. The forms in which it is used are (1) ground limestone, (2) marl, (3) air slaked lime, (4) quick-lime, (5) water-slaked lime.
Lime is applied to soils to correct what is called acidity of the soil, which arises from a large removal of basic material by crops and drainage water and to other minor causes. This condition is widespread in soils and is in creasing so that the agricultural lime industry is growing rapidly. The tendency in the busi ness at the present time is to produce ground limestone rather than burnt lime. The ground limestone is somewhat more bulky to transport, but it is much easier for the farmer to handle and it may be kept without danger of heating. Owing to its bulk and the large quantities ap plied per acre lime is not usually transported long distances, and this is one reason why the grinding mills are scattered so widely over the regions in which limestone is found. Dolomitic limestone may be used on most soil with profit, but the trade usually prefers a lime with only a small percentage of magnesia.
Home Mixing of Fertilizers.— Fertilizers are ordinarily sold as (1) complete fertilizers containing nitrogen, phosphoric acid and potash, which in different mixtures are to be found in different relative amounts; and (2) incom plete fertilizers, or raw material containing only one of these ingredients. Authorities at a number of the experiment stations have urged that it is in many cases more profitable for the to purchase the incomplete fertilizers and mix them •himself, The arguments ad vanced in favor of this practice are that the materials can be purchased more cheaply in that form than when mixed by the manufacturer; that they can be used in the proportion desired, which may effect a saving in the amount of some ingredient, and that the form in which each ingredient is present is then known, which is not always the case when mixtures are pur chased.
On the other hand, it is more difficult to obtain the raw materials from the small dealer, and when purchased they are not generally so finely ground as they are in the mixtures.
State Control of Fertilizer Sales.—In most States•in which fertilizers are largely used laws are in effect compelling manufacturers or dealers in fertilizers to state the actual amounts of the fertilizing ingredients contained in the fertilizers offered for sale, and also to state in what form each of these ingredients exist. A chemical control is provided and a penalty im posed for any failure to comply with the law. The control authorities publish each year a state ment of the commercial value per pound of nitrogen, phosphoric acid and potash in each of the various forms in which they occur in fertilizers. Fertilizer control is in most States attached to the State agricultural experiment stations, and information concerning the pur chase and use of fertilizers may be obtained from these institutions Statistical.— The quantity of fertilizers manufactured and consumed is increasing in all portions of the crop-producing world; and especially in the United States there has been a rapid increase from one decade to another. In 1859 the value of the entire output of the fertil izer factories was $891,344; in 1869, $5,815,118; in 1879, $23,650,795; in 1889, $39,180,844; in 1899, $44,657,385 and in 1909, $193,960,213. Not all of this is used on farms in this country, there being $8,700,640 worth exported in 1910. The imported fertilizer materials consisted largely of nitrate of soda and potash salts, while the exported fertilizers were animal ref use and phosphate fertilizers.
Although the commercial fertilizer industry is little more than half a century old, the sale of fertilizers in the United States in 1909 amounted to $114,883,000, an increase of 115 per cent as compared with the expenditure in 1899. This large quantity of fertilizer was largely used in a rather narrow strip•of country lying along the Atlantic seaboard. The South Atlantic states show a higher rate of increase in expenditures for fertilizers between 1899 and 1909 than any other, such increase amounting to 162.3 per cent, but Ohio shows an increase of 155 per cent and Indiana of 141 per cent for the same period, which indicates a westward movement of the practice of using fertilizers.
As is naturally to be expected, the first settled and longest cultivated portion of the country is that using the greatest quantity of fertilizers. This region lies nearest to the large centres of population and hence of con sumption; it produces crops of greatest acre value; and it is so situated that the distances which it is necessary to transport fertilizers are generally less than they would be for the non fertilizer-using portion of the country. It is true in the United States, as it is in Europe, that a large consumption of fertilizers usually goes hand in hand with a highly developed and intensive system of agriculture.
T. Lvrrizroil LYON, Professor of Soil Technology, Cornell Univer sity.