No. 5. 



Burnt Cluy as a Manure. 



119 



disuse. CoBBETT, whose erratic course is so 

 strongly and universally condemiied, tried it 

 ^vith no Utile success durinij his sojourn in 

 this country. His [irincipal experiments 

 were made, I think, on Long Island, and are 

 detailed helow. Loudon says that the oldest 

 bock in u'hich it is mentioned was published 

 more tlian a century since. lie states that 

 the benefits have been irreatly exaj^tjerated — 

 thouj^h on clayey soils it is ot" considerable 

 advantage. The mania for burning clay at- 

 tained its height in England in 1815; and in 

 a itiw years thereafter its most strenuous ad- 

 vocates were indisposed to say much on the 

 subject. AiTON, in his Farmers' INIagazine 

 says ; " I regret that the discoverers of 

 florin grass and of the effects of burnt clay, 

 have so far overrated their value. Both are 

 useful and proper to be attended to — the grass 

 to be raised on patches of marshy ground, 

 and used as green food to cattle, and the 

 burnt earth as a corrector of the mechanical 

 arrangement of a stubborn clay soil ; and I 

 have no doubt that if they had been only re- 

 commended for those valuable purposes, they 

 would have been brought into more general 

 use than they yet are, or will be, till the pre- 

 judices against them arising from the disap- 

 pointment of expectations raised high by too 

 flattering descriptions, are removed." The 

 advantages of burnt clay are briefly set forth 

 in the following synopsis, and which embo- 

 dies the " practical experience" of intelli- 

 gent men on both sides of the Atlantic. 



1. When clay is burnt to a state of ashes 

 (like brick dust) it will so remain, and can- 

 jiot return to its original state of clay unless 

 by the application of acids. Consequently, 

 says Alton, an admixture of that with a 

 strong adhesive clay must evidently operate 

 as a powerful manure, by changing the me- 

 chanical arrangements of the latter. By 

 this means it is rendered more friable, af- 

 fording a greater facility to the percolation 

 of redundant moisture, and to the spreading 

 of the roots of vegetables in quest of food. 

 If the clay or earth thus burnt abounds with 

 vegetable fibre, the soot or carbonic matter 

 acquired by the operation, would probably, 

 for one season at least, operate as a stimulus 

 to the growth of plants. Alton, however, 

 expresses the opinion that as the subsoil is 

 frenerally used for burning, it is impossible 

 that any considerable quantity of vegetable 

 matter can be found in it. 



n. " The calcareous matter in the soil is 

 said to be calcined and formed into lime by 

 this process." This argument by many 

 writers is considered more plausible than 

 solid. But while the opponents of this sys- 

 tem contend that little or no perceptible 

 effect can be produced when the matter burnt 

 «r torrefied is applied as a manure to other 



soils, they admit one princij)al point, wliich 

 is, '• that some (lualitii^s in particular soils, 

 unfavorable to vegelalioii, may be corrected 

 by burning; and that in some other instances 

 the fire may render the clay more nutritive to 

 plants." VVhatever effect may be producedi, 

 except that of rendering the soil more friable, 

 must be temporary, and therefore soon run 

 out. 



in. A writer in the Farmers' .lournal, 

 1819, says that the action of bur7U clai/ is 

 threefold, and may be manifold. '' It opens 

 the texture of stubborn clays, gives a drain 

 to the water, spiracles to the air, and affords 

 t^ the roots facility of penetrating. Clay 

 ashes burnt from turves containing an ad- 

 mixture of vegetable matter, consist in some 

 small proportion of vegetable alkali or pot- 

 ash, a salt which is known to be a good 

 manure. It frequently happens that a stiff 

 cold clay is impregnated with pyrites, a 

 compound of sulphuric acid and iron. Al- 

 though the chemical attraction between these 

 two bodies is so strong that it is one of the 

 most difficult operations in the arts totally to 

 free iron from sulphur, yet a very moderate 

 heat sublimes a large portion of the sulphur. 

 The iron is then left at liberty to re-absorb a 

 portion of the redundant acid, which is too 

 generally found in these soils, and thereby 

 sweetens the land; and it is probable that 

 the bright red or crimson calx of iron which 

 gives coloring to the ashes when over-burnt 

 is beneficial to vegetation, in the present 

 case, inasmuch, as it is, of itself, one of the 

 happiest aids to fertility. Curwen notices 

 that clay ashes do not benefit as a top dressing 

 on grass, which is in part to be explained by 

 reason that the ashes, when spread on the 

 surface of the grass, cannot exert mechanical 

 action on the soil in the ways enumerated. 

 Neither can the calx of iron come so imme- 

 diately in contact with the particles of the 

 soil, for the production of any chemical ef- 

 fect, as it would do if the ashes were plough- 

 ed in. In short, like many other manures 

 which are laid on the surface, unless it con- 

 tain something soluble, which may be wash- 

 ed into the ground by rains, it does very 

 little good ; and the feeble proportion of 

 vegetable alkali is probably the only soluble 

 matter the ashes contain." 



IV. The salutari/ effects of fire on soils is 

 thus described by the late Richard Peters, 

 Esq. " I could give many instances of the 

 great utility of fire in fertilizing land which 

 have passed under my own observation, both 

 recent, and of very old date. I can show 

 numerous spots in fields on which large col- 

 lections of weeds were burnt twenty years 

 ago, which now exhibit, and have so done 

 ever since the operation, a most extraordinary 

 comparative fertility, in ground, the whole 



