Banner from top of front page of the Oct. 1, 1921 Saturday Evening Post

October 1, 1921

POISON GAS — By Robert Crozier Long

ALMOST with the intens­ity of their former war interest Ger­man men of sci­ence are pur­su­ing a new pois­on-gas cam­paign, which is to achieve what the chlor­ine and mus­tard-gas argu­ment lam­ent­ably failed in, and put the repub­lic at last and really über Alles in der Welt. Even case-hardened German­o­phobes watch this cam­paign with sym­pathy. Its pur­pose is to raise the badly sunken crops to a level high­er than that of pros­per­ous pre­war times; to double or even treble the food pro­duc­tion; to make an at present ill-nour­ished people inde­pend­ent of for­eign flour; and thereby to restore the trade bal­ance and res­cue a battered Reichs­mark exchange from ever-in­creas­ing inan­i­tion. The secret of this, in Prus­si­an pro­fess­or­i­al lan­guage, is car­bon fer­til­iz­a­tion of crops; in ordin­ary lan­guage it is the diver­sion into and dis­tri­bu­tion among grow­ing plants of car­bon­ic-acid gas, the CO2 of school books, a gas fatal to human beings and anim­als in very mod­er­ate quant­it­ies, but bene­fi­cial and indis­pens­able to plant life. Through the applic­a­tion of adequate doses of this pois­on gas wheat ears are doubled in weight and size; rye, which in the Ger­man's daily bread plays a great­er role than wheat, is equally increased; and on impov­er­ished soil rise pota­toes, cab­bages, peas, toma­toes and fruits sur­pass­ing the prize pro­duc­tions of mod­el farms. From red cur­rants to pump­kins no fruit has been dis­covered that can­not be pois­on-gassed into extra size and nutri­tious­ness. And all this magic, which will revo­lu­tion­ize agri­cul­ture and ulti­mately the trade of the world, will be achieved at a very mod­er­ate cap­it­al expendit­ure, and at prac­tic­ally no oper­at­ing cost at all.

Car­bon fer­til­iz­a­tion is in its infancy, and being an infant its bril­liancy may be exag­ger­ated. There are vis­ion­ar­ies who already talk of onions as big as pump­kins and of pump­kins as big as bal­loons. They see in dreams the ima­gin­ary mon­strous veget­ables raised with H. G. Wells’ Food of the Gods. This is an absurdity. But Friedrich Riedel, of Essen, the man who has done most to solve the prob­lem prac­tic­ally, proved by con­vin­cing fig­ures that any coun­try's food crops may be doubled with CO2. Nat­ur­ally not at once. “Bad things,” said Samuel John­son, “wax more rap­idly than good”; and if Prus­sia's ablest war chem­ists needed only three weeks to find means for pois­on-gass­ing enemies into etern­ity the bene­fi­cial pois­on-gass­ing of plants will need years or dec­ades of labor before the world's food con­di­tion can be mater­i­ally improved. Yet this move­ment is no longer merely exper­i­mental. For more than three years car­bon fer­til­iz­a­tion has been suc­cess­fully car­ried on on a great scale; and the tri­umphs achieved—veri­fied by minute records and con­firmed by con­ver­sion of author­it­at­ive doubters—give fair col­or to Riedel's pre­dic­tion that with­in vis­ible time a gas equip­ment will be as obvi­ous a part of an effi­cient farm as it already unluck­ily is of an effi­cient mil­it­ary force.

Nature No Longer Trus­ted

THE dom­in­ant per­son­al­it­ies in the new pois­on-gas devel­op­ment are three. First in time is Dr. Hugo Fisc­her, of Essen; first in the the­ory of the sys­tem is Dr. F. Borne­mann, now of Heidel­berg, formerly pro­fess­or of farm­ing at Ber­lin Agri­cul­tur­al High School; and first as prac­ti­tion­er is Riedel. As prac­ti­tion­er Riedel leads not only because he has gassed veget­ables, fruits and grain crops on much the largest scale, but because he first made the pro­cess easy and cheap by draw­ing his car­bon­ic-acid gas from the blast fur­naces of great smelt­ing works.

With all three exper­i­menters the under­ly­ing prin­ciple is the same. This prin­ciple is that car­bon is the most import­ant con­stitu­ent of all veget­able mat­ter; and that though the defi­ciency of oth­er vital crop con­stitu­ents is made good as a mat­ter of course by farm­ers when they apply fer­til­izers, the dom­in­ant ques­tion of a suf­fi­cient car­bon sup­ply is left to take care of itself. For car­bon the farm­er puts his trust in nature. That he does so is a para­dox. For nature, as he learns in his first les­sons on farm­ing, can­not always be trus­ted to sup­ply nitro­gen, potassi­um and phos­phor­us in suf­fi­cient quant­it­ies; why then should nature be relied on to sup­ply the pre­cise, minutely rationed quant­ity of car­bon, neither more nor less, which best fosters a lux­uri­ant and healthy growth? In the light of pure sci­ence the para­dox is increased. In the remote Car­bon­ifer­ous peri­od plant life, as coal meas­ures prove, was immeas­ur­ably rich­er than to-day—the biggest mod­ern fern is a pygmy beside the Paleo­zo­ic fern—and in this Car­bon­ifer­ous period, phys­i­cists agree, the atmo­sphere was charged much more heav­ily than to-day with car­bon­ic acid gas. Abstract sci­ence has long known these facts; applied agri­cul­tur­al sci­ence has ignored them. It is not long since Ger­many’s lead­ing agri­cul­tur­al chem­ist, the late Prof. Edward Heiden, pro­claimed in a prac­tic­al hand­book that the suf­fi­cient sup­ply­ing of car­bon to crops and fruits was a mat­ter with which no farm­er needed to trouble his head.

The chem­ic­al the­ory behind the entirely con­trary prac­tice of Fisc­her, Borne­mann and Riedel is simple. Car­bon provides the bricks and mor­tar of every plant, of its root, stalk, leaf, ear, fruit and seed. The water con­tents, which in some plant parts out­weigh everything else, are here ignored. Water con­sti­tutes as much as 75 per cent of the potato, against 24 per cent nutrit­ive organ­ic mat­ter, and it con­sti­tutes 13 per cent of the rye grain against 85 per cent. If both water and min­er­als—between 1 and 2 per­cent—are left out of account, 49 per cent of the aver­age plant con­sists of car­bon, against 43.5 per cent oxy­gen, 6.3 per cent hydro­gen and 1.2 per cent nitro­gen. Of car­bon, that means, is used forty times as much as of nitro­gen, for which in the form of nitrates every farm­er provides as a mat­ter of course. Of cel­lu­lose 44.4 per cent is car­bon; of lignin, the wood mat­ter, 55 per cent; of sug­ar 40 per cent; of straw 45 to 50 per cent; of albu­men 50 to 4 per cent; and of oils and fat actu­ally 76 per cent. Car­bon sup­plies from nearly one half to two-thirds of the sub­stance of every plant mater­i­al which has value as food or in indus­tri­al use.

For growth, in addi­tion to the four chief ele­ments men­tioned, every plant requires nine oth­er ele­ments. It requires sul­phur, sili­cium, chlorium, sodium, mag­nesium, iron, cal­cium, potassi­um and phos­phorus. Of these, with the excep­tion of cal­cium, potassi­um and phos­phorus, all soils con­tain enough. The prac­tic­al farm­er recog­nizes this when he applies lime, potash salts and phos­phates; and hav­ing applied also nitrates he has done, he holds, his duty to the full. The duty of sup­ply­ing car­bon is per­formed, he is con­vinced, by the atmo­sphere. The quant­ity of car­bon­ic acid in the atmo­sphere, it is true, is small. Meas­ured by volume it is .03 per cent, or three parts in 10,000, against 78.04 per cent of nitro­gen, 20.99 per cent of oxy­gen, .94 per cent of argon, and traces of four oth­er gases.

That is aver­age coun­try air; tests taken out­side Munich forty years ago showed only .02 per cent of CO2, or two-thirds of nor­mal; and a Lon­don Decem­ber day once revealed 14.1 er cent, or nearly five hun­dred times the nor­mal. At most, the quant­ity is small. But the quant­ity of 30: actu­ally avail­able for plant growth is great­er than the aver­age pro­por­tion in the air. The gas is brought down to the soil dis­solved in rain, and evap­or­a­tion re­leases it. The quant­ity released var­ies accord­ing to the height of the cloud and the slow­ness and fine­ness of the rain. The organ­ic mat­ter in a hum­ous soil is con­tinu­ally decom­posed by bac­teria, worms and minute anim­als, and the car­bon­ic-acid gas is set free. Organic, in par­tic­u­lar animal, fer­til­izers are decom­posed by the same means with the same res­ult. Like all liv­ing cells, plant roots breathe and release CO2. These four addi­tion­al sup­plies of the gas play a great role in crop growth. The tests of Pro­fess­or Borne­mann show that between one-sixth and one-sev­enth of the car­bon con­tained in a nor­mal crop is derived from gas exhaled from the soil.

Plant Diges­tion

Plants, as every farm­er knows, assim­il­ate the atmo­spher­ic and the exhaled car­bon­ic-acid gas, and apply the car­bon therein for pro­duc­tion of their organ­ic sub­stance. By the leaves the gas is decom­posed into its two con­stitu­ents, car­bon and oxy­gen, and the oxy­gen is exhaled. The path to acquire­ment of this ele­ment­ary know­ledge was long. A Swiss, Charles Bon­net, first dis­covered that leaves give off a gas; Priestley, an Eng­lish­man, iden­ti­fied this gas as oxy­gen; a Swiss, Sene­bier, dis­covered that the oxy­gen is the rejec­ted ele­ment of inhaled car­bon­ic-acid gas; and Sene­bi­er’s fam­ous pupil, Theodore Saus­sure, mem­ber of a fam­ily which pro­duced three first-rank sci­ent­ists, developed the doc­trine, and proved it by feed­ing plants with car­bon­ic-acid gas. The gas enters the slit-shaped leaf pores—of which a single cab­bage leaf con­tains 11,000,000; it is dis­solved in a liquid which sat­ur­ates the del­ic­ate walls of the green or chloro­phyll cells; it passes, so dis­solved, into the interi­ors of the cells; and it is here decom­posed into the retained use­ful car­bon and the super­flu­ous rejec­ted oxy­gen. That is assim­il­a­tion. For assim­il­a­tion three things are neces­sary: A liv­ing green plant sub­stance, air con­tain­ing car­bon­ic-acid gas, and power. The power is light. Bey­ond that very little is known about a plant’s meth­ods of self-con­struc­tion. The com­plic­ated pro­cesses by which car­bon, with oth­er mater­i­als, is worked up into cel­lu­lose, lignin, albu­men, starch, sug­ar and fats, are not known at all. There are prob­able the­or­ies and plaus­ible assump­tions, but noth­ing more.

Without suf­fi­cient light no plant will assim­il­ate car­bon. Yet the first dis­cov­ery that plant growth can be increased by an extra sup­ply of CO2 was made, a hun­dred years back, in the dim and smoky Eng­lish city of Manchester. That plants do not grow well in indus­tri­al cit­ies is not due to the excess of gas, but to bad light­ing, and to sul­phur­ic acid, smoke, dust and oth­er impur­it­ies in the air. Saus­sure proved this by com­par­at­ive exper­i­ments with plants in ordin­ary air, in air enriched with vary­ing extra doses of car­bon­ic-acid gas, and in pure car­bon­ic-acid gas. Giv­en very good light­ing, he showed, plants grow best in an atmo­sphere con­tain­ing 8 per cent of CO2, or 260 times the nor­mal; no light, however strong, he proved fur­ther, increases assim­il­a­tion if the sup­ply of CO2 is insuf­fi­cient; and finally, even with the strongest light­ing, more than 8 per cent of the gas is injur­i­ous. A later exper­i­ment showed that the yel­low light rays best foster assim­il­a­tion; orange and red are less effect­ive; and blue and viol­et rays pro­duce prac­tic­ally no assim­il­a­tion at all.

Strik­ing Res­ults

On the eve of the exper­i­ments of Fisc­her, Borne­mann and Riedel no ser­i­ous doubt exis­ted that car­bon fer­til­iz­a­tion was a the­or­et­ic­ally prac­tic­able and use­ful help in agri­cul­ture. But the prac­tic­al res­ults were nil. Reas­ons for this were, first, the sup­posed tech­nic­al dif­fi­culties and, second, the incur­able obstin­acy of even sci­entif­ic farm­ers. The tech­nic­al dif­fi­culty is, however, merely a com­mer­cial one, a ques­tion of oper­at­ing costs versus extra crop profits. The cost of pro­du­cing and dis­trib­ut­ing car­bon­ic-acid gas on the large scale needed even for a veget­able garden would be far greater, it was believed, than the increased value of the yield; and the cost of pois­on-gass­ing whole fields of wheat, corn and oats would be mon­strously out of pro­por­tion to the addi­tion­al value of the crop.

Even at first sight this opin­ion looks like a pre­ju­dice. The same farm­ers who held it found it prac­tic­al to pay for car­riage of potash from Europe to the cent­ral plains of the United States, for car­riage of phos­phates for equally great dis­tances, and for car­riage of Chile niter from a remote corner of South Amer­ica to a noble’s estate on the slopes of the Urals. The argu­ment that these fer­til­izers are abund­ant and need only trans­port­a­tion no longer applies. For sev­en years past the only nitrates used by Ger­man farm­ers have been syn­thet­ic­ally pre­pared out of the atmo­sphere by the costly and com­plic­ated Haber Bosch and cal­ci­um pro­cesses. There is noth­ing more far-fetched in adding car­bon diox­ide to the air than in extract­ing nitro­gen out of it; and fifty years ago prob­ably every farm­er would have pro­claimed the second plan to be the more far-fetched and vis­ion­ary of the two.

The only real unsolved prob­lem, that means, was the prob­lem of com­mer­cial prac­tic­ab­il­ity, the ques­tion of sup­ply­ing car­bon­ic-acid gas at a reas­on­ably low cost. Fisc­her, the first of the recent Ger­man invest­ig­at­ors, found the prob­lem insol­uble. He there­fore ignored it, and exper­i­mented only with the expens­ive cyl­in­der CO2 of com­merce. He began by treat­ing plants with air enriched to .09 per cent of gas, or three times the nor­mal, and he ended with .66 per cent, or twenty-two times the nor­mal. His res­ults, always meas­ured by com­par­is­ons with non­gassed plants grown under sim­il­ar con­di­tions, were:

Great­er size and weights of the plants as a whole;

Con­sid­er­ably earli­er blos­som­ing and ripen­ing of fruits;

Very much big­ger and rich­er fruits.

His last exper­i­ments, made togeth­er with Pro­fess­or Borne­mann, were with the ordin­ary Ger­man winter wheat and winter rye, which sup­ply the greatest part of Ger­many's bread­stuffs. These were planted both under glass and in the open. The res­ults of gass­ing were in all cases good. The gassed wheat and rye pro­duced more and stronger shoots than the ungassed, they ripened weeks sooner, and they car­ried big­ger ears. Seeds which, ungassed, yiel­ded ten ear-bear­ing straws, yiel­ded when gassed is many as thirty-two. The best res­ults were obtained under glass, and the res­ults with rye were bet­ter than with wheat.

Borne­mann fol­lowed with inde­pend­ent open-air exper­i­ments, last­ing 130 days, on winter wheat, oats, bar­ley, beans and mus­tard. Gas was dis­trib­uted from ordin­ary small light­ing-gas pipes, which the later large-scale exper­i­ments of Riedel show to be unsuit­able; and the oth­er con­di­tions, owing to poverty of resources, were unfa­vor­able. The superi­or­ity of the gassed crops was less than Riedel attained, but it was emphatic. Gass­ing increased the yield of wheat 25 per cent, of oats 41 per cent, of bar­ley 24 per cent, and of beans 63 per cent. Borne­mann drew the con­clu­sion that car­bon fer­til­iz­a­tion is an indis­pens­able part of really sci­entif­ic farm­ing. For com­mer­cial farm­ing it was, under present con­di­tions for pro­du­cing and dis­trib­ut­ing gas, imprac­tic­able. The use of cyl­in­der gas was out of the ques­tion. It was reserved for a young West­phali­an engin­eer, Friedrich Riedel, to solve the prob­lem com­mer­cially. Solu­tion, he reasoned, lay in the util­iz­a­tion of the already exist­ing unlim­ited sup­ply of waste indus­tri­al gases. Con­fid­ent of suc­cess, ignor­ing the gibes of cer­tain pro­fess­ors of agri­cul­ture who told him that though he was a first-rate engin­eer he had yet a great deal to learn about farm­ing, he set to work.

Hugo Stinnes—Prus­sia's Mor­gan, as some call him, a mer­chant of Mülheim, as he mod­estly calls him­self in a Reich­stag mem­ber's list—next comes on the scene. With 170 Stinnes indus­tri­al under­tak­ings, cap­it­al­ized at 5,500,000,000 marks, few Ger­man scenes can be ima­gined on which Stinnes does not appear. Riedel's exper­i­ments in car­bon fer­til­iz­a­tion were made in con­nec­tion with the Deutsch Lux­em­burg smelt­ing works at Horst on the Ruhr, the first of the 170 cor­por­a­tions to be con­trolled by Stinnes and the nuc­le­us of the vast elec­tro-min­ing trust which to-day embraces most of the rest. Stinnes and his chief dir­ect­or Voe­g­ler gran­ted to Riedel the use of the whole resources of the Deutsch- Lux­em­burg, its land, its machines, its work­men and its labor. Out of that rose the first great car­bon farm in the world. The sow­ings and plant­ings were made on a gran­di­ose scale; there were no eco­nom­ic­al obstacles of the kind that had hampered the first two invest­ig­at­ors; and the res­ult was a suc­cess which soon put an end to doubt in the most skep­tic­al pro­fess­or­i­al brain.

Riedel's first work was to con­struct two big glass houses as near as pos­sible to Stinnes' blast fur­naces, and to pre­pare two fields for open-air exper­i­ments a little farther off. One glass house and one field were for ordin­ary cul­tiv­a­tion; the oth­ers for cul­tiv­a­tion in air arti­fi­cially fer­til­ized with CO2. Minute care was taken to insure that the soil, light­ing and mois­ture should be identic­al for gassed and ungassed plants. The gas was dis­trib­uted from per­for­ated tubes ten cen­ti­meters in dia­met­er with ori­fices of about two cen­ti­meters in dia­meter, placed at reg­u­lar inter­vals; and pres­sure in the tubes was main­tained by elec­tric fans. In the glass house for gass­ing were laid two tubes, one low down, bent into twelve-meter squares, the oth­er higher, in shape of a main tube with radi­at­ing smal­ler tubes. In his fields Riedel laid per­for­ated con­crete pipes, arranged in quad­ri­lat­er­als, so that equable dis­tri­bu­tion was insured in any wind.

Flue Gases Used

The gas used came dir­ectly from the blast fur­naces, and con­tained 5 per cent of C02, which is less than the 8 per cent found most effect­ive by Saus­sure, but is 160 times stronger in car­bon­ic than in ordin­ary air. The only treat­ment under­gone by the gas between expul­sion from the blast fur­naces and dis­tri­bu­tion to the plants was puri­fic­a­tion from smoke and dust. Puri­fic­a­tion from sul­phur­ic acid was not neces­sary, as the iron ore is smelted with coke; and puri­fic­a­tion from car­bon monox­ide—CO—was need­less, because this gas is harm­less to plants. But as car­bon monox­ide is highly pois­on­ous to human beings and anim­als Riedel later removed it by pre­lim­in­ary com­bus­tion. He remarks that as a rule this is unne­ces­sary, as most indus­tri­al works in their own interests allow no car­bon monox­ide to escape.

Riedel's exper­i­ence is that 5 per cent of car­bon­ic-acid gas is the most effect­ive on the aver­age. But how much of this mix­ture is really avail­able for the plants is not exactly known. In the open air, part of the CO2 is speedily blown away by wind; and if there is no wind it is thinned by dif­fu­sion. In glass houses the con­tinu­ous for­cing in of a 5 per cent mix­ture under pres­sure keeps the whole air of the house at that strength. By that is explained the fact that in Fisc­her's exper­i­ments the greatest addi­tion­al crop yield obtained from plants grown under glass.

After the first year of suc­cess Riedel increased the dimen­sions of his exper­i­ments. He built three more glass houses and added 40,000 square yards to the area of his fields. In the new fields he laid his per­for­ated cement tubes under­ground. His aim was to sup­ply the extra dose of gas from the low­est pos­sible level, so that it would reach the leaf pores exactly as does gas set free from the soil. This dimin­ishes the quant­ity of gas dif­fused upwards or blown away before it is caught in the pores; and the effi­ciency of the fer­til­iz­a­tion is very largely increased.

Riedel's exper­i­ments embraced nearly all of the more import­ant cul­tiv­ated food plants, and also some flowers. Flower tests proved use­ful for study of the effects of gass­ing upon blos­soms, and one of the first tri­umphs was a more than four-and-a-half-fold increase in the blooms of the helio­trope plant. In fields or in glass houses were planted—some­times in both, and always on a suf­fi­ciently large scale to pro­duce reli­able aver­ages—bar­ley, pota­toes, turnips, sug­ar beet, rape, toma­toes, gher­kins, lupines, soy­beans, spin­ach, fen­nel and the castor-oil plant.

Import­ant Res­ults

The first plant­ings, which covered only six of the plants men­tioned, took place in 1917 in the middle of May. Four weeks later, when the first green shoots were show­ing above the soil, car­bon fer­til­iz­a­tion began, and with it began the mak­ing of hourly and daily obser­va­tions and the keep­ing of minute records. With­in two or three days the dif­fer­ence between sizes and con­di­tions of gassed and ungassed plants was seen. The dif­fer­ence invari­ably favored the gassed plants. It was at first con­fined to stalks and leaves; later, when blos­soms and fruits appeared, the dif­fer­ence was equally marked; and finally the har­vest­ing of the root and tuber crops proved that the advant­age from gass­ing was gained by every part of the plant.

First and most import­ant of res­ults of gass­ing is the greatly increased leaf growth. The leaves of Riedel's gassed plants were lar­ger and their stalks thick­er and firmer. The leaves of man­gel-wurzels gassed in the open air aver­aged in area 70 per cent more than the leaves of ungassed plants. Ungassed castor-oil plants had leaves 58 cen­ti­meters long; gassed plants had leaves 100 cen­ti­meters long. The gassed castor-oil leaves bore a whit­ish bloom sim­il­ar to the bloom on grapes. Leaves of gassed plants were unusu­ally firm and fleck­less, and they were colored a deep­er green, prov­ing bet­ter assim­il­a­tion and a rich­er pro­duc­tion of the pre­cious chloro­phyll, the green col­or­ing mat­ter upon which the health of all plants, para­sit­ic fungi excep­ted, depends.

This bet­ter leaf pro­duc­tion in the early growth stage is espe­cially import­ant, be cause the leaf's abil­ity to absorb car­bon­ic-acid gas depends upon its size. There­from fol­lows the fact—proved when Riedel inter­rup­ted the gas sup­ply—that the young gassed plant with its abnor­mally big leaves extracts an extra dole of car­bon also out of the ordin­ary air, so that car­bon fer­til­iz­a­tion, even if car­ried on for only a few days in the early growth period, largely increases the ulti­mate size and weight of the crop.

Riedel found not a single excep­tion to the rule that car­bon fer­til­iz­a­tion mater­i­ally increases the weight and size of fruits and roots. The smal­lest advant­age of any gassed fruit or root crop over an ungassed crop was 15 per cent. In all oth­er cases the advant­age was at least 36 per cent; often the advant­age was more than 100 per cent, and some­times it was more than 200 per cent. These fig­ures were for the whole crops of beds or patches of a defined size.

Riedel declares that car­bon fer­til­iz­a­tion without oth­er fer­til­izers pro­motes plant growth more effect­ively than all the ordin­ary fer­til­izers when these are used without arti­fi­cially sup­plied car­bon. Ordin­ary fer­til­izers, he says, used in ordin­ary air increase an aver­age crop by half a kilo­gram per square meter, which is 18 per cent of the crop, where­as car­bon fer­til­iz­a­tion applied without the ordin­ary fer­til­izers brings an aver­age increase of 40 per cent. This is the exper­i­ence in fields, where res­ults are less favor­able than under cover. If a field gets both car­bon fer­til­iz­a­tion and ordin­ary fer­til­iz­a­tion the aver­age increase of crop is 82 per cent.

Riedel, Borne­mann and Fisc­her draw from this the con­clu­sion, valu­able for all farm­ers, that fer­til­iz­a­tion with nitrates is usu­ally over­done, and that part of the heavy cost is need­lessly incurred. The full quant­ity of nitrates usu­ally used could be taken advant­age of by crops; but in prac­tice it is not taken advant­age of, because the sup­ply of car­bon is rel­at­ively too small. The dis­sat­is­fied farmer, however, often adds more nitrates at a time when he should be resort­ing to car­bon fer­til­iz­a­tion, and so help­ing his crops to the more act­ive assim­il­a­tion which would enable them to use an abund­ant nitrates sup­ply.

At first sight this the­ory is of no interest to the ordin­ary farmer, who is not yet in a pos­i­tion to sup­ply extra car­bon by arti­fi­cial means. But the three pion­eers of the the­ory declare that it has a prac­tic­al imme­di­ate mean­ing, because car­bon fer­til­iz­a­tion to a lim­ited extent is with­in the reach of every farm­er in pos­ses­sion of a har­row or a spade. This lim­ited car­bon fer­til­iz­a­tion is achieved simply by insur­ing that the soil is well sup­plied with organ­ic mat­ter, and by keep­ing the sur­face looser than is at present the rule.

The secret of nat­ur­al car­bon fer­til­iz­a­tion is merely the keep­ing of a con­tinu­ally loose sur­face and the pre­ven­tion of incrust­a­tion. Back­ward farm­ers believe vaguely that by this means they air the land, and less back­ward farm­ers ima­gine that they let oxy­gen in. The real profit from a loose and por­ous sur­face soil is that it lets the under-sur­face car­bon­ic-acid gas rise freely towards the leaves. Borne­mann proves from exper­i­ments last­ing sev­enty-eight hours that the CO2 emit­ted by a con­tinu­ally broken sur­face is three times as great as from an incrus­ted sur­face. The increase of crops by pois­on gas, it fol­lows, is no vis­ion of remote sci­entif­ic magic; it is an aim attain­able by every prac­tic­al farm­er at very little cost.

Car­bon fer­til­iz­a­tion by arti­fi­cial means on a great scale is anoth­er mat­ter. All the three exper­i­menters are optim­istic; but they take dif­fer­ent views as to times and prac­tic­ab­il­it­ies. For the present only small oper­a­tions are com­mer­cially prac­tic­able, says Borne­mann. Berry fruits, vines and veget­ables can already be car­bon fer­til­ized with fin­an­cial suc­cess. Fisc­her goes fur­ther. The waste gases of industry, he pre­dicts, will soon be set stream­ing through young forest plant­a­tions. Riedel has no doubt that even under present con­di­tions grain crops can be car­bon­ized with profit. For that, he admits, the car­bon­ic-acid gas of com­merce is too dear. Of the future he says: “Just as cer­tain as we have to—day spe­cial plants for pro­du­cing elec­tric power, so we shall some day have CO2 works erec­ted for the fer­til­iz­a­tion of our fields.” Costly and com­plic­ated these works will be; but they will be less costly and com­plic­ated than the equip­ment at present needed for pro­duc­tion of syn­thet­ic air niter.

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