American Farmer p. 32 (June 5, 1829)
(From the Transactions of the London Hort. Society.)

On the use of Charcoal Dust as a top-dressing for onions, and as a cure for the clubbing in cabbages, &c. Communicated in a letter to the Secretary—by Mr. Thomas Smith, gardener to Matthew Bell, Esq., F. H. S. at Woolsington, Northumberland.

Sir,Having seen some papers in the Transactions of the Horticultural Society upon the cultivation of onions, but none that took any notice of a disease to which these roots are very subject, I venture to lay the following experiments and their results before the society.

The garden I superintend, is a very wet, stiff soil, upon a strong clay, and without any declivity. For several years my crops of onions were nearly all destroyed by a grub, and by mouldiness coming on about their roots at various stages of their growth; sometimes when they were about the size of what we call scallions, at other times when they were beginning to form a bulb, and even when the bulb was formed. As soon as the. disease takes place it may very readily be perceived by the onion blade assuming a glaucous green colour, but very soon after changing to yellow, and the leaves at the same time rather flag. I tried various quarters in the garden, and found that there was a difference in them, some of them producing more of the disease than others. I also tried several experiments to prevent the disease taking place: but none had the desired effect, until I made use of charcoal dust spread upon the top of the ground intended for onions, about half an inch thick, before the seed is sown (the ground being previously well dug and manured,) and merely scuffled in with the point of a spade, so as to mix the top soil and charcoal dust together. Nothing more is after required beyond managing the crop in the usual way.

For these last six years I have had most excellent crops of onions, and not the least appearance of any infection. My first experiment I made on a bed, fifty feet long and five feet wide, prepared in the usual way, one half the bed was dressed with charcoal dust, and the other half without it; the part on which the dust was laid had an excellent crop of onions, it remained quite clean and free from any disease, while the part to which the dust was not applied was entirely destroyed by the grub and by mouldiness.

I subsequently resolved to try the effects of the dust on a larger scale; I therefore had the whole of the quarter prepared for onions, and divided it into eight beds of the same size as before; four of the beds were treated with dust, the other four remained without it. The result was the same as before, the beds where the dust was applied bore a good clean crop, whilst the others were affected. Having had two years proof of the good effects of charcoal dust in preventing the disease from taking place upon the onion in one quarter, I have since tried it upon different quarters, with the best success.

The charcoal dust ought to be kept quite dry, which is easily done by placing it in a round heap, and covering it closely over with turf till it is wanted.

I have also found that the application of charcoal dust effectually prevents the clubbing in the roots of cabbages, &c. I had been accustomed to use lime fresh from the kiln for that purpose, and always with considerable advantage; but since I have made use of the charcoal dust upon different quarters of the garden, and any of the Brassica kind was subsequently planted there, the clubbing has entirely disappeared. I planted, some time back, a quarter with cauliflower plants, which never arrived at maturity, being very much injured with the club. In the spring of the following year I had the same quarter prepared for onions, with charcoal dust upon it as soon as the onions were cleared off in October, I had it well dug over, and planted it immediately with early cabbages, which all arrived at maturity the ensuing spring, without the least appearance of clubbing.

Remarks by the Editor of the New England Farmer—Charcoal is not only useful as an antidote against insects, but is a valuable manure. Dr. Deane stated that he had long observed where coal kilns have been burnt, the ground has discovered a remarkable fertility for many years after, and more especially when it has been a cold and wet soil.The dust of the coals and that of the burnt turf have conspired to produce this effect. Hence I have concluded the small coals, or the dust from coal kilns, spread over sour meadow lands would answer the end of a good manure. Being extremely porous, the pieces of coal imbibe much of the superfluous water, as well as increase the heat on the surface, as all black substances do. And when the weather becomes dry, they discharge the moisture, partly into the soil, when it grows dry enough to attract it, and partly into the air by the action of the sun upon it.

It is stated in the last Philadelphia edition of Willich's Domestic Encyclopedia, vol. i. page 655, that "a friend of Dr. Mease informed him, that some years since, nearly all the cucumber and melon vines in New Jersey were destroyed by a fly or bug. One day he had occasion to ride by a miserable hut in the woods, and perceiving a very flourishing patch of cucumbers, he was induced to dismount and examine it. On approaching the spot he found it had formerly been a charcoal heap. He took the hint, and by strewing powdered charcoal round about the vines, when they first come up, preserves his cucumbers effectually."