AN INTERESTING EXPERIMENT

The essential facts of plant growth have long been known. The bulk of the food that all plants need comes from the atmosphere, taken in by the leaves as carbonic acid gas. Other foods are taken in through the roots as dissolved in water. Of these latter, nitrogen, potash and phos­pho­rus are not found in our soils in sufficient quantity to insure the greatest plant growth, so they are commonly supplied to the plants in the form of fer­til­izers or manures.

It has been supposed that the carbon required by the plant was present in the atmosphere in quantities sufficient to insure the plant's greatest development, or, if not, certainly no means of supplying additional carbon to the plant at a profit has been known.

Experiments are now being carried on in Ger­many which indicate that it may be possible, by fertilizing the atmosphere with carbonic acid gas, to increase the yields of our common garden vegetables by 100 per cent. to 300 per cent. and do it profitably, that this may be practicable not only in the green­houses but in the out-doors as well.

To quote from the Scientific Amer­i­can:

“Whereas atmospheric air at present is relatively poor in carbonic acid, of which it contains only about .03 per cent., at an early period in the development of our planet, when this was covered with the luxuriant forest our coal deposits are derived from, it comprised incomparably greater quantities of this gas. This fact suggested the idea of heightening the fertility of the soil by increasing its carbonic-acid content and thus producing conditions resembling those of antidiluvian ages. In order to enable such a process to be carried out on anything like a com­mer­cial line, a cheap source of carbonic acid had, of course, to be provided.

“This was found by Dr. Fr. Riedel, of Essen-on-Ruhr, in the combustion gases escaping from all factories, but most abundantly from blast furnaces, and which so far had been allowed to flow out into the atmosphere without serving any useful purpose. He accordingly set to work designing a process for which patents were obtained and which was put to practical tests on a large scale. Three green­houses were at first erected, one of which served as testing-room, while the two others were used for checking purposes. The testing-room vas supplied with purified and burnt blast furnace exhaust gases through a line of punctured piping traversing the whole green­house in a forward and backward direction. The gas supply was started on June 12, that is to say, at a time when plant growth was at its height.

“On account of the careful cleansing and complete elimination of constituents such as sulfur, the gas was found to exert no harmful effects. On the contrary even a few days after starting the test, there could be observed in the testing-room a more luxuriant vegetation than in the checking-houses. The leaves of the castoroil plant in the green­house supplied with gas were found to reach more than a yard in span, whereas the largest leaf in the checking-houses was only about a foot and a half in width. Plants submitted to the influence of carbonic-acid gas also showed a marked advance with regard to their height. With the tomatoes planted in part of the green­house the weight of the same number of fruits in the testing-room was 175 per cent. more. With the cucum­bers planted at the same time a somewhat slighter dif­fer­ence was noted, an increase of 70 per cent. An interesting phe­nom­e­non noted in this connection was that, while the cucum­bers in the checking-houses would exhibit bright spots, those in the testing-house, on account of the more plentiful formation of chlorophyl, were of a dark green color throughout.

“Experiments in the open air were made simultaneously with these green­house tests, a square plot of ground being encircled by punctured cement pipes from which a continuous supply of exhaust gases was escaping. The wind, mostly striking the ground at an angle, would drive the carbonic acid in a variable direction toward the plants, thus allowing extensive areas to be supplied with the fertilizing gas. On the opposite side of the green­house plant there was provided for checking purposes a plot of the same size submitted to no carbonic-acid gas, the soil in the two plots being of the same quality Samples were derived from the best portions of the checking-field, but from the center of the field submitted to the action of carbonic-acid gas, the increase in yield in the case of spinach was found to be 150 per cent., with potatoes 180 per cent., with lupines (a legume) 174 per cent., and with barley 100 per cent. The potatoes in the field submitted to the action of carbonic-acid gas were found to ripen much more quickly than in the checkingplot. Later and more extensive exper­i­ments developed an increase of yield of potatoes of 300 per cent.”

It certainly is an interesting exper­i­ment.