The following analysis by Stöckhardt* of the flesh and bones of the whale may not be without interest in this connection : 299. The following tables illustrate the composition of some of our more common fish fertilizers. Those in Table A are from analyses reThose in Table B are reported by Prof. S. W. ported by the writer. * Per cent. soluble in water, 1.76; per cent. soluble in ammonium citrate, 2.47. Chemische Ackersmaun XVI, 1870, 52. + Report of Connecticut Agricultural Experiment Station, 1876, p. 63. Waste from faulty manufacture and use of fish fertilizers. 300. An enormous loss results to our agriculture from the waste of fish that might be saved, from faulty manufacture of fish into fertilizers, from wrong use of the fertilizers when made, and from the exportation of the best products to Europe, where their value is better understood. This loss will be prevented in proportion as the nature and uses of fish manures are learned. 51. THE USE OF FISH FERTILIZERS IN AGRICULTURE. Chemistry of plant nutrition. 301. Not only farmers and merchants, but many manufacturers as well, have a very poor understanding of what constitutes the value of fish as fertilizers, and how they may be most economically utilized. It will be well, therefore, to consider briefly some of the principles that decide the value and usefulness of fertilizers in general, and of fish products in particular. Fish manures, like other commercial fertilizers, are valuable because they supply plant-food which crops need and soils fail to furnish. Their main value depends upon their content of nitrogen and phosphoric acid. These are the most valuable and costly ingredients of commercial fertilizers. Plants, like animals, require food for life and growth. A part of the food of plants is supplied from the atmosphere, the remainder is derived from the soil. No ordinary cultivated plant can thrive without a sufficient supply of each of a number of substances needed for its food. With an abundance of all of these in forms in which the plant can use them, and with other circumstances favorable, the plant will flourish and the yield be large. But if the available supply of any one of them be too small, a light yield is inevitable. For instance, potash is an essential ingredient of the food of plants. If all the other conditions for a profitable crop of corn or potatoes, or other plants, are fulfilled in the soil, except that potash is deficient, the crop will inevitably fail. But if the potash be supplied the yield will be abundant. The chief use of fertilizers is to supply the plant-food which the soil lacks. Vegetable and animal substances, and manures and soils as well, contain, besides water, two kinds of materials, the so-called organic matter and the mineral matter or ash. The organic matter consists chiefly of the four chemical elements, carbon, oxygen, hydrogen, and nitrogen. We do not need to trouble ourselves about the first three of these in fertilizers, because they are supplied to the plant in abundance by the atmosphere and the soil through the leaves and through the roots. But the nitrogen is an important ingredient of fertilizers. It is, in its pure state, a gas, and makes up about four-fifths of the air. Combined with hydrogen it forms ammonia; combined with oxygen it is known as nitric acid. In these and other combinations it occurs in minute quantities in the atmosphere, and in considerable quantities in soils and manures. Plants are unable to make use of the pure nitrogen of the air, though some, if not all, absorb a very little combined nitrogen from the atmos phere. By far the largest part of the nitrogen of plants is absorbed from the soil through the roots. From the facts that nitrogen is available to plants only in certain combinatious, that it is slow to form and easily leaves these compounds, that it readily escapes from manures and soils into the air, and is leached away by water, it is one of the most commonly deficient and hence the most costly ingredients of the food of plants. The mineral matter or ash of plants is derived entirely from the soil. It consists of several ingredients, known as potash, soda, lime, magnesia, iron, silica, sulphuric acid, phosphoric acid, and chlorine. Essential ingredients of plant-food. 302. The results of a vast amount of this sort of experimenting prove that no agricultural plant can attain full growth without a sufficient supply, through its roots, from the soil, of potash, lime, magnesia, iron, phosphoric acid, sulphuric acid, and some compound of nitrogen. Besides these, chlorine, and perhaps silica, are sometimes, if not always, indispensable, though in very small proportions, to complete development. If any one of these essential ingredients be lacking the plant will suffer in growth and development. Exhaustion of soil by various crops. 303. Crops take from the soil, then, the materials needful for their growth; and these are rightly called "plant-food." Some soils yield large crops many years in succession without manuring. They do this because they contain large stores of the ingredients of plant-food, as potash, lime, nitrogen, &c., and because these are furnished in available forms, so that the plant can readily use them. As a rule, after cropping for some time, the point is reached where the natural resupply of plantfood is insufficient to produce large crops. In other words, in the so-called "poor," "worn-out," or "exhausted" soils, the natural strength is insufficient for profitable production. In order to know what fertilizers to use on such soils we must know what ingredients of plant-food are deficient, and what manures will best supply them. An idea of the essential ingredients of plant-food removed from the soil in cropping may be obtained from the table below, which is calculated from the extensive tables of analyses of plants by Wolff. Materials removed from the soil by various crops. Large quantities of silica, and small quantities of soda, chlorine, and iron, are also removed from the soil by every crop. Iron is necessary to the growth of all agricultural plants, but in very minute quantity. In many cases sall amounts of chlorine seem to be requisite. Silica, if needed at all, which is quite doubtful, is required only in extremely minute proportions. Soda does not appear to be an essential ingredient of plant food. In so far as these latter are essential ingredients of plant food, they are furnished in abundance by every ordinary soil. Ingredients most commonly lacking in worn-out soils, and hence most important in fertilizers; nitrogen, phosphoric acid, and potash. 304. For our present purposes, then, we have to consider only the potash, lime, magnesia, sulphuric acid, and nitrogen. Of this list the magnesia is commonly, though not always, supplied in sufficient quantities in even "worn-out" soils. Sometimes its presence in fertilizers may be of considerable importance to crops. Sulphuric acid and lime are more often deficient, and hence one reason of the good effect so often observed from the application of lime and plaster. The remaining substances, the nitrogen, phosphoric acid, and potash, are the most important ingredients of our common commercial fertilizers, because of both their scarcity in the soil and their high cost. It is in supplying these that fish guano, phosphates, and bone manures are chiefly useful. In brief, then, in order that crops may grow, they must have at their disposal an adequate supply, in available forms, of each one of a certain list of essential ingredients of their food. Soils differ in respect to their supplies of these food ingredients. The crop cannot rise above the level of the lowest ingredient in the food supply. The chief use of fertilizers is to fill up the gaps. Principles to be observed in the manufacture and purchase of fertilizers. 305. The cardinal principle to be observed by the farmer in the purchase of fertilizers is, to— Select those which furnish, in the best form and at the lowest cost, the ingredients of plant-food that his crops need and his soil fails to supply. The principle that should guide the manufacturer should be, toEconomize all available materials in his manufacture so as to furnish the valuable ingredients in the best forms in products of high grade and uniform composition, and at the fairest practicable rates. The most important ingredients of our fertilizers, because the most rare and costly, are nitrogen, phosphoric acid, and potash. The two first are the most important. These are supplied in large proportions in fish. Composition, character, costs, and uses of fertilizers in general. 306. It will be to our purpose, then, to note briefly : 1. The composition of some of our more important commercial fertilizing materials, particularly those which, like fish manures, contain nitrogen and phosphoric acid; in other words, the analyses of these fertilizers. 2. The comparative costs and values of the active fertilizing ingredi. ents in these articles; or, in other words, the commercial valuations. |