VOL.6, No. 9
HIGH-SCHOOL ESSAYS
1437
THE RELATION OF CHEMISTRY TO AGRICULTURE*
Read the platforms on which Smith and Hoover so determinedly stood. Read the speeches given by these men in the last presidential campaign. You will find that farm relief was one of the strongest if not the strongest point at issue. The farmer is promised relief from these economic condi. tions which he can neither foresee nor control. It has always been thus from Lincoln's time right up to the present time of President-elect Hoover. But this sort of farm relief commonly means price-fixing by the government, a guarantee that the farmer will receive what his labor and product are worth. This must be carried out on an economically sound basis and therefore must not burden taxpayers with the payment of a disguised subsidy to farmers. Because this is not an easy thing to do, these promises do not mature. The most effective aid in any instance is to remove the cause of the suffering. What is the reason for the present bad conditions of agriculture? A satisfactory market cannot be obtained, resulting in a surplus which is wasteful. How may this he remedied? Herein the agricultural chemist takes the leading r61e. In the first place the food products raised must be as perfect as possible in order to receive the best prices. The condition of the soil is largely responsible for the success or failure of a crop. Out of all the known elements only thirteen are necessary for plant growth. They are hydrogen, oxygen, nitrogen, and chlorine of the gases, potassium, magnesium, sodium, calcium, and iron of the metals, and carbon, phosphorus, sulfur, and silicon-non-metallic solids. Hydrogen, oxygen, and carbon are obtainable from the air and water. The others are dissolved in soil water in the form of salts, and under ordmary con* Prize-winning high-school essay. 1928-29.
ditions the majority of these are easily supplied; however this is not the case with nitrogen, potassium, and phosphorus, which very often have to be replaced by fertilizers. Due to the ignorance of our ancestors, the soil has been robbed of many of its necessary elements by failure to replace those taken away from the soil in plants and by the burning of trees for the leaching of the ashes. The successful farmer should be instructed by the agricultural chemist whether his fertility account is properly balanced, so that these losses may be restored. The better use of green manures and plant residues, the conservation of animal manures, and the rotation of leguminous plants with the maintenance of soils in a condition suitable for the growth of these nitrogen-fixing organisms will all contribute toward keeping the soil fertile. However, there will still be need for further application after all these resources have been used to the fullest extent. This is accomplished by the use of chemical fertilizers. Nitrogen may be supplied to the soils lacking in this material by use of ammonium sulfate, given off as a byproduct from gas and coke plants, sodium nitrate found in Chile, and from various nitrogen products obtained from the air. Though the need of nitrogen fixation from the air, because of the possible exhaustibility of ammonium sulfate and sodium nitrate together with the high cost of Chilean nitrate, has been known for nearly thirty years, the World War furnished the real impetus. The three most outstanding processes of nitrogen fixation are the arc, cyanamide, and direct synthetic--this latter being based upon the Haber process first developed in Germany. g he arc process necessitates a great amount of power, and therefore is only practical where power is cheap. The cyanamide process uses only about one-fourth the amount of power per unit of nitrogen of that required for the arc process; however, if it is to be successfully operated, it also demands cheap power. In the direct synthetic-ammonia process power causes very little concern. As the product, ammonia, of the direct synthetic process can be easily converted into a compound suitable for fertilizer, and because it uses only onefourth as much power as the cyanamide process, the arc and cyanamide processes are gradually giving way to the direct synthetic process. There are three important sources of commercial potassium, the German and French mines, the salts recovered from evaporation of sea water, and wood ashes. There is as much potash in the rocks as nitrogen in the air, but the nitrogen is uncombined, while the potash is combined with silicon and alumina from which it is very hard to be separated. Potash is also given off as a by-product in cement, alcohol, sugar, and blast furnace industries. However, all these potash by-products could furnish only fifteen per cent of our needs. Some potash deposits have been found in Nebraska, Utah, California, and other states, but it can neither be easily nor cheaply
separated from the other elements. Thus we see that the bulk of our potash is still being imported. Soils deficient in phosphorus may be enriched by the application of three substancesfine-ground natural rock, acid phosphate, and double super-phosphate. Although the United States has not the monopoly on phosphorus that Chile has on nitrogen and Germany on potash, we need not worry about our need of these products, as some of the world's most important deposits are found in Tennessee, South Carolina, Florida, A~kansas, and Kentucky. Large deposits of the rock were also found in the western states, Utah, Idaho, and Wyoming. In many cases the unproductiveness of a soil is due not to an absence of any particular element but to an injurious excess of acid, alkali salt, or some other substance. The acid in the soil may be neutralized by the application of lime. Excess of alkali may be prevented by irrigation and drainage or use of gypsum. The chemists are now working to develop more efficient fertilizers in concentrated forms, eliminating a great amount of the shipping cost. If in the future phosphoric acid may be obtained more cheaply, a salt, ammonium phosphate containing both nitrogen and phosphorns in a highly concentrated form, would be obtained by directly combining phosphorus ' acid with ammonia. There are various other nitrogen, pbosphorns, and potassium compounds which may be combined in varying amounts to form a more efficient fertilizer. It is evident that in time to come, due to the wi~leninguse of fertilizers and the decreasing of present sources of these products they will he manufactured on a strictly chemical basis. However, there are various difficulties which must be overcome. Not only must a plan he worked out for the manufacture of ammonia and phosphoric acid so cheaply that they could compete with the present sources of nitrogen, but the farmer must be educated in the use of these new methods before they can come into wide use. By this brief survey of the soil it can easily be seen that by the application of certain chemical fertilizers in the correct proportions found by chemical analysis chemistry is certainly now solving the problem of soil fertility and will continue to in the future. The chemist's work does not end bith making it possible fortbe farmer to have his soil in perfect condition, but also protects the plant after it has begun to grow against various diseases, insects, microbes, and fungi. Price-fixing by Congress could not possibly have any effect on the workings of these little organisms, but chemistry certainly has. The yearly losses caused by the cotton boll weevil have been estimated to exceed $300,000,000. Calcium arsenate has been found to be a valuable insecticide for this and is now scattered by airplane. This means of appli-
cation, however, is often wasteful, and it remains with the chemist to devise a plan by which this may be scattered without the present waste. Forms of sulfur were the only chemical sprays known to the ancients. Cato has written about these. As with fertilizers so with sprays. It was left to the modem chemist to find the real reasons for the actions of certain materials and to discover new and more efficientways. Bordeauxmixture is used as an effectivefungicide on potatoes, tomatoes, and other crops. With the great increase of San Jose scale in the Middle West, interest was revived in lubricating oil sprays, and several simplified formulas for their manufacture have appeared. The use of a trap crop to collect insects where they can be killed without loss to the main crop is a common farm practice. The chemists found that this attraction was due to some volatile substance in the plant. If this could be separated and synthesized, its use in combination with the poison would furnish a very effective means by which the insect would be lured to its own death. Amy1 acetate has been used in this way for the destruction of grasshoppers, geraniol for attracting the Japanese beetle, and trimethylamine for the cotton boll weevil. Hydrocyanic acid and other volatile poisons have been used to combat scale upon fmit trees and weevils in stored cereal products. To perfect these insecticides, fungicides, and sprays so that they will be more efficient, cheaper, and less dangerous to both plant and consumer is a feat which will necessitate the highest chemical knowledge. The damage to agricultural product3 caused by the attack of certain microbes opens a wide field for investigation. Souring of milk, rotting of fruit and timber, and swelling of canned goods are examples. The chemical action of these processes is very imperfectly understood, and the chemist must study these changes and provide a means by which they may be prevented. Not all the work of these micro-organisms, however, is detrimental. Bacteria and yeasts, when properly controlled, are exceedingly useful to the farmer. Cheese, vinegar, sauerkraut are valuable products resulting from their work. Quack grass-with the exception of the Canadian thistle, the most destructive weed known-has in recent experiments been successfully killed, roots and all, by the use of the chemical, sodium chlorate. This is indeed a very important discovery, Qsmany of the richest soils in Northem and Eastern United States are now so overrun with the weed that cultivation is almost impossible. This idea of killing weeds with chemicals is old, but heretofore none has been found that is not injurious to the soil. Losses through insufficient fertilization, diseases, insects, and fungi are by no means the only f a m ~losses. The problem of surplus is doubtlessly the most important agricultural enigma of the present day. Here again the chemist is solving the problem.
The farmer has heretofore paid attention only to the production of crops for net weight in making food products and clothing. Now through breeding experiments and constant chemical supervision he is providing his growing plants with the necessary amount of raw materials which will make possible a maximum yield of the desired product whether it is starch, cellulose, oil, protein, or any other substance. According to Professor 0. R. Sweeney of Iowa State College, some 3000 known industrial products can be made from cornstalks, oat chaff, cottonseed hulls, peanut shells, and straw. Wall board is made from sugar cane bagasse. Sixteen million tons, the yearly waste of cornstalks, may be converted into 8,000,000 tons of paper. Corn has been used in the manufacture of starch, dextrin, glucose, sirup, dextrose, gluten, oil, and cattle feed. There is also the possibility of converting straw into tar, illuminating gas, acetic acid, wood alcohol, xylose, furfural, oxalic acid, strawboard, and lumber. The utilization of unmarketable lemons has been accomplished by the manufacture of citric acid, lemon oil, marmalade, cattle feed, and pectin. Oil from the cottonseed, once a problem, now is a very profitable product. These are only a few of the many that might be mentioned. It can be truthfully said that not nearly all the possibilities of chemical utilization of our crops have yet been realized. Not nearly all the farm products grow from the soil. Indeed the farm animals play a great part in agriculture. Here also we see the need of chemical aid. As new kinds of machinery are';.apidly taking the place of horses and oxen for work on farm, the feedmg of animals for production of milk and meat rather than work has become the practice. Therefore, feedmg materials must be investigated in order to find the best growthproducing kinds of proteins. In the old days a certain amount of carbohydrates, fat, proteins, and mineral matter was thought to be sufficient for an animal. But as a result of investigation, i t has been found that not all proteins are alike in tissue building. It was also formerly thought that no other minerals were needed besides salt and calcium phosphate. We now know that this is not true and that it is necessary to balance the acid-forming with the base-forming elements in the diet. According to Henry P. Armsby, Founder and First Director of the Pennsylvania State College Institute of Animal Nutrition, the difference between the energy value before consuming and that lost in utilization represents the net energy value of a food. Iodine has been introduced to prevent goiter in animals raised where the soil is deficient in iodine. It has been found that the iodine taken up by cereal crops is lodged in the germ of the grain. This hitherto re-
jected portion of the cereal may come into wide use as a feeding material, as it contains not only iodine but organic phosphorus, vitamins, and other foods. We see now that soil fertility is maintained by the aid of chemicals and plants protected by application of chemicals. Therefore, if the farmer will have good crops, he is dependent on chemistry. Due to the fact that we cannot possibly consume all the farm production as food, it has become necessary to devise plans by which there would be no waste. This chemistry has done. The investigation of chemists on food rations for farm animals has told the farmer what foods he can most profitably and with the best results feed to his animals. I believe that in the future the bulk of our food will continue to be raised from the soil, but I also believe that the farmer of the future will not confine himself so closely to food production as formerly. Real farm relief will be secured when the factory and farm cooperate in carrying on great industries. The agricultural chemist has already laid the foundation of many new and rich industries. The general nation-wide belief is that agriculture is doomed to die or is now dying a pitiful death. On the contrary, I believe, after seeing all the things chemistry has done and may in the future do for farming, that agriculture is now just establishing itself upon a sound and profitable basis as other industries. Bibliography "Soil Fertility and Permanent Agricultura" C. G. Hopkins, Ginn & Company, Boston, 1910. "Creative Chemistry," Edwin E. Slosron, The Century Company, New York, 1919. "Chemistry in Agriculture," J. S. Chamberlain, The Chemical Foundation, Nrw York, 1926. "Spraying, Dusting and Fumigating of Plants," A. F. Mason, The Macmillan Company, New York, 1928. Literary Digest, October 20, 1929, "Chemical Farm Relief by Ennobling Farm Waste," pp. 22, 23. Literary Digest, January 12, 1929, "Chem~calCrops to Make Farms Pay," p. 18. "Muscle Shoals, Nitrogen and Farm Fertilizers," R. 0. E. Davis, The Annals of the American Academy, 135, 157-64 (January, 1928). "Agricultural Chemistry," lecture delivered by Dr. C. A. Browne a t Columbia University, New York, August 11. 1926. "Attack Farm Problem by Utilizing Wastes," released for publication November 22, 1928, by United States Department of Agriculture. "Phosphorus in Fertilizer," William H. Waggaman, United States Department of Agriculture, Bureau of Soils.
