THE RELATION OF CHEMISTRY TO AGRICULTURE* "At the head of all the sciences and arts, a t the head of civilization and progress, stands, not militarism, the science that kills, not commerce, the art that accumulates, but agriculture, the mother of all industry, and the maintainer of human life."' Agricultural chemistry offers the fundamental scientific basis upon which to build a sound and permanent agriculture, therefore, i t should be of v i t a l interest to every American. For the last three hundred years, the American people have been living on the virgin lands of the United States. It has been only within recent decades, when all 'the best unoccupied agricultural areas have been staked out in homesteads, that the question of maintaining and improving soil fertility has begun to receive serious consideration. The farmer must develop intensive methods of agriculture and increase the productivity of his fields, in order to feed and clothe our rapidly increasing population. P l a n t s a r e made of soil JOHN LIVAK material and air material. Of the nintey-two elements that comprise the earth, only thirteen (hydrogen, oxygen, nitrogen, chlorine, potassium, magnesium, calcium, iron, sodium, carbon, sulfur, phosphorus, and silicon) are essential to plant life. Three of these, hydrogen, oxygen, and carbon, are obtained from the air and water. The ten others, in the form of salts, are dissolved in the water, which the plant obtains, by osmosis. In the case of all but three of these elements, the amount deposited in the soil is sufficient to supply the demands of the plant. The three deficient elements are nitrogen, phosphorus, and potassium. Consequently, man must supply these to depleted soils, if he wishes
* Prize-winning high-school essay,
' James A. Garfield.
192G27.
plants to grow. When we realize that a bale of cotton (500 pounds) deprives the soil of 84 pounds of nitrogen, 15 pounds of phosphorus, and 41 pounds of potassium, we can easily comprehend why the soil loses fertility so quickly if no plant food is put back. Further, when we know that these elements are fatal or useless to plant life in the elemental form, but, that fixed in a compound they are available as plant food, we begin to understand the difficult problem that man must solve. Chemists, as early as 1840, began research on this probleq. It was the German chemist, Justus von Liebig, who first discovered that soil fertility could be maintained by the application of chemicals. This important discovery led to our modern commercial fertilizers. The world's principal source of nitrogenous material in the past has been the nitrate beds of Chile. While these deposits are enormous, they are exhaustible; hence, the chemist, believing in being prepared, has resorted to artificial sources for the production of soluble nitrogen compounds. He has been so successful that, a t the present day, the synthetic air-nitrogen products supply most nitrogen to agriculture; by-product ammonium sulfate comes second; and Chilean nitrate falls into third place. The chief source of ammonium sulfate is coal; ammonia being a by-product when coal is burned to produce coke. About 80,000 tons of available nitrogen were produced in 1917 by this method. There are several methods for the fixation of atmospheric nitrogen. In the United States, the most successful one, commercially, is the combining of nitrogen with calcium carbide a t the temperature of the electric furnace to f o m cyanamide. (The Muscle Shoals Plant was designed to produce 110,000 tons of ammonium nitrate, annually.) By far the greatest quantity of phosphoric add used in fertilizers is derived from the mineral phosphates, the chief source of which is the United States. Besides supplying our own needs, we export $7,000,000 worth to Europe annually. At present, the pebbles dredged up from the bottom of Florida lakes and ponds are the chief source, but the supply is limited. There is no need to worry, however, for deposits in the states of Idaho, Wyoming, Utah, and Montana have been estimated to contain more than 6,000,000,000 tons of high-grade rock, besides many times this amount of lower grade phosphates. Germany and France, a t present, have the natural monopoly of potash. The United States had to depend on this source, until the chemist developed artificial methods of producing potash. His task was not as easy as it may appear to the casual observer, for, although, potash compounds are as cheap as dirt, every handful of gravel containing 10 per cent potash has it in combination with silica, from which it cannot be easily separated. In 1924, through the aid of chemistry, the United States produced 44,000 tons of potash salts. The sources were natural brines, dust from cement
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mills, dust from blast furnaces, alunite, kelp, molasses residue from distilleries, and waste liquors from beet-sugar refineries. Recent governmental investigations have resulted in the improvement of methods of recovering potash from the mineral, greensand, deposits of which cover large areas in the states of New Jersey, Delaware, and Maryland. Further discoveries in the state of Texas have strengthened the belief that commercial deposits of potash underlie considerable areas in this region and only await comprehensive surveys with core drilling to be accurately located. Taken as a whole, an independent supply of American potash in the future seems a probability. The chemist, having obtained inexhaustible supplies of plant food, next directs his attention to the welfare of the plants. Plants, like human beings, are subject to disease, and their illnesses must be diagnosed, if we wish a plentiful supply of food. Sometimes, microscopic organisms, which cause diseases like anthracnose, rust, smut, and, sometimes, visible and familiar insects like the boll-weevil, corn borer, and Colorado beetle eat away the living cells of the plant. The losses to American agriculture from the depredations of the cotton boll-weevil alone exceed $300,000,000 a year. One of the most successful means of combating this pest has been by means of calcium arsenate, which is now applied by airplanes. The chemist, besides fist applying insecticides and fungicides, has done much to make them more effective and less costly. He has pointed out that if calcium arsenate is caused to assume a positive charge of electricity, it is attracted to the leaf, which is negatively charged. Experiments have shown the adhesiveness of positively charged calcium arsenate to be 200 times greater than that of the standard product. Another chemical success, too recent to be adopted industrially, is the extraction of a substance, trimethylamine, from the cotton plant, which attracts the boU-weevil and lures the insect to its own destruction. Thus, by instituting chemical warfare against plant pests, the chemist has lowered cost of production for which we, the consumers, should be thankful. The agricultural chemist, having nourished and doctored the plants, again appears on the scene when the crops are harvested. This time he employs his creative genius, and, through the medium of by-products, he has utilized surplus products, as well as produce of inferior quality, in some cases doubling the value of the crop. An effective example is shown in the case of corn. In 1925, 3,013,000,000 bushels of corn were raised in the United States. Of this amount, 50,000,000 bushels were worked up by the factories into 800,000,000 pounds of corn sirup; 600,000,000 pounds of starch; 230,000,000 pounds of corn sugar; 625,000,000 pounds of gluten feed; 90,000,000 pounds of oil, and 90,000,000 pounds of oil cake. A kernel of corn is composed of three parts, the germ, the body, and
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the hull, each of which breaks up into hundreds of useful products. The germ produces corn oil which, in turn, becomes table oil, dyers' oil, soap, glycerine, or rubber substitute, just as the wizard chemist decrees. The germ produces, also, oil-cake and oil meal, which are utilized as cattle food. The body breaks up into starch, dextrose, glucose, corn sirup, hydrol, tanners' sugar, cerelose, white, canary, envelop, and foundry dextrin, British gum, amidex, and gluten. The gluten subdivides into vegetable glue, vegetable casein, and gluten meal. The hull is utilized in the form of bran. Having thus utilized the kernel, the chemist, ever economical, has turned the cob (2,000,000 bushels of which were thrown away annually) into a gum, suitable for bill-posting and, also, into a varnish. The chemist, always thrifty, has utilized cull oranges, grape-fruit, and lemons, and has profitably converted them into citric add, marmalade, candied peel, lemon oil, pectin and cattle feed. Further, he bas found a use for apple pulp in the manufacture of pectin; and, after the pectin is extracted, he bas economized still more, by pointing out that the pomace made suitable cattle food. For another example of chemical utilization, let us consider cotton. Cotton has been known to the West since the time of Alexander the Great, but the attention of mankind has been focused so long upon the valuable fibers or seed hairs of the cotton plant, that chemists overlooked, for many centuries, other numerous possibilities of utilization. It is only since the Civil War that the possibilities of the cotton seed, which was either thrown away or burned as fuel, were realized. Nevertheless, the chemist has made up for lost time, for, in 1925, he added $200,000,000 to the value of the cotton crop by converting the cottonseed into articles of commerce. In this short discussion, it would be impossible to name the countless useful things that a ton of these seeds produce. But when we know that from the linters come such articles as felt, rope, carpets, smokeless powder, varnishes, celluloid, and artificial silk; from the hulls, fertilizer, cellulose, fuel, and feed; from the meats, soap, flour, cosmetics, oleomargarin, artificial leather, candle pitch, and glycerin, we begin to realize the creative genius of the chemist. The extent of agricultural chemistry is so vast that even here the chemist did not stop. Ever on the outlook for more economical methods of production, he has discovered substitutes for overworked plants. For instance, rubber is as essential to agricultural production and marketing of crops at the present time as it is to urban industries, but, it is expensive. The chemist sought a substitute for the juice of the rubber tree. He discovered that vulcanized corn oil, mixed with pure rubber, gave the latter greater durability and elasticity, besides lessening the cost. Iso-
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prene, an oily, volatile, hydrocarbon (CSH~)obtained by the distillation of caoutchouc, is another successful substitute, scientifically, though not industrially. Recent research has also resulted in obtaining a quality of rubber from the African euphrobia tree, which is comparable with that of para. This discovery is too modern to be put into practical use. At present, the chief source of rubber substitute is the Mexican plant, guayale, which is not cultivated extensively to eke out our supply of natural rubber. In 1870, governmental chemists introduced a new plant, the navel orange, into the United States. The new industry proved so successful that there is now an average annual production of 8,600,000 boxes of oranges and 3,000,000 pounds of orange by-products. Thus was obtained a plentiful supply of the popular and healthful fruit. Another example of the chemist's power is discovered in the production of sugar-beets. Although reference to the sugar-beet is made in ancient Babylonian catalogs of plants as early as 710 B.C.; it was not until 1747, that a German chemist, Andrew Marggraf, made the important discovery that sugar of identically the same properties as that obtained from the sugar cane could be extracted from the beet. The industrial utilization of this discovery broke England's monopoly of the sugar industry which she had acquired through the West Indies. Another important phase of agricultural chemistry, which could be mentioned, is that referring to law enforcement. From time immemorial, articles and products of utility have been subject to adulteration, misbranding, or other forms of deception, practised by unscrupulous persons. In modem times, the chemist plays a most useful and essential r8le in detecting adulteration of fertilizers, cattle-feeds, insecticides, fungicides, and other agricultural necessities. Through his influence, efficient State and Federal laws have been passed, which require the accurate labeling of such products as to their chemical composition, thus protecting the farmer against deception. The chemist protects the consumer of agricultural products in like manner, for the milk, butter, grain, fruit, simp, and other products, which the farmer sells must come up to a certain standard of excellence, if he does not wish to be penalized by some one of the laws against adulteration. Nearly half a century ago, a fertilizer, selling a t $32 a ton, was put on the market. The fertilizer contained mud dug from under the waters of a harbor. Someone ventured to doubt the efficacy of the trace of ocean salts in the mud as a stimulant for crops. The skepticism spread, and, finally, resulted in the chemical analysis of the mud fertilizer. The analysis unearthed the fact that the stuff ww worth $1.02 a ton as a filler, but was useless for other purposes. Much fraud is perpetrated upon the consumer through the sale of adulterated insecticides, sold under misleading trade names, the cost
of the products being far above the value of the constituent ingredients. A product of this kind was offered for sale a number of years ago. The manufacturers claimed that it was not only of great value and efficiency as an insecticide and fungicide, but was also useful as a plant food. Chemical tests showed a total of only 0.07 per cent of plant food, while, as an insecticide, it was practically worthless. It seems almost inevitable that every new valuable discovery in agricultural chemistry should immediately be put into an illegal use. The value of commercial pectin was no sooner discovered than a host of fraudulent manufacturers began to use it as an adulterant in fruit jellies. Ethylene gas, used to impart a yellow color to mature citrus fruits of a green color, was immediately misapplied hy unscrupulous producers to give immature oranges, lemons, and grapefruit a false appearance of ripeness. Hundreds of examples of this nature could be cited and the chemist must be ever on the alert in order to protect the consumer from deception. Thus, in five ways; namely, by feeding the soil, being plant doctor, creating by-products, finding substitutes when necessary and acting as detective, the chemist has been of great value to the farmer, and through him, to us, for as Theodore Roosevelt truly states, "The strengthening of country life is the strengthening of the nation." Chemistry is the basis which underlies the existence of soils and crops and animals. The remarkable achievements of the agricultural chemist in the past bear witness to this. Yet, the chemist, working alone, cannot predict a successful future. Let us, as a nation, cooperate with him, and thus show him our appreciation of the enriching science of chemistry, which utilizes Nature's products to the utmost. I wish to acknowledge the valuable aid rendered me in the writing of this essay by the volume, "Chemistry in Agriculture," Edwin E. Slosson's book, "Creative Chemistry," and the United States Department of Agriculture.
