

THE AGRICULTURAL GAZETTE 



299 



wmm 



7- uy xrilOS OF THE FINER PARTICLES 

 *J¥aMHY MATTE! ON VEGETATION. 



OF EAR! 



i«i*d from tb# Geirnan of the late P&ofewor Schuele* 

 ***»*■*■" 02 ie University uf Tubingen.] 



loped. 

 me in 



The injurious action of magnesia anpen d to ca * e » it: bad act<Mi aa a poison. It is obvious, from woat ha*- 



these experiments to depend especially on a I b ?. eu ,"^f ^^ 

 physical cause ; 1 always remarked that the substances 



III. 



(Continued from p. 283.) 



quicklime) 



This earth 



The ash of several 



* 



r 



it&ui 



their process of vegetation, deposit 



I ib (or pure _ in .. 



tly enters into mixture with vegetable juices 

 it found, next to sUica, most frequently in 

 JL aafces of plants, and consequently particular 

 ZlilS ea and species of plants, and even the same plants 

 °T ^-p to their different periods of development 

 exhibit remarkable differences. 



^^ of trees is very rich in carbonate of lime ; the 

 aJao of many leguminous seeds is rich in this 

 ^th while, on the contrary, the sulks of many of the 

 CmJiifi. so abundant in silica, contain only a small pro- 

 -5oTof lime. Plants of the same kind commonly 



08 lime in their early growth, but a larger 

 proportion in their advanced stages. Many aquatic 

 Sots, several of the Myriophylla, Characeee, and dif- 

 fc«ntAlg», during their process ■ _ 



lipe, even in crystalline grains, upon their inner or outer 

 graces, although the water in which these plants de- 

 vclM* themselves contains only a very little carbonate 

 of lime, which is not deposited on other organic bodies, 

 lathe botanical periodical •< Flora," I have communicated 

 »ine more exact observations on the Hy drums crvstal- 

 kpliorus, an indigenous aquatic plant found in Wurtem- 

 berg. It appeam from all these circumstances to be 

 highly probable, that on the perfect cultivation of various 

 plants, lime acts favourably as a virtual means of nourish* 

 ment ; and on the contrary, to be injurious to others : 

 accordingly we observe that Chrysanthemum segeumi, 

 Uca vulgaris, and various species of Carex, become 

 more rare whan clay lands are improved by lime and 

 marl. Mixed with soil, lime has the property of pre- 

 venting the formation of the free acids, which in wet 

 clay lands easily result from the decomposition of organic 

 matter or other process of oxidation. It renders acids 

 already pn ut in the soil innoxious, provided they are 

 not in too great an amount. Particles of humus, in an 

 almost insoluble state, have become through its agency 

 soluble, and converted into a beneficial means of nourish- 

 ment for plants. Heavy clay soils by its means are 

 rendered lighter, lose their too great tenacity, and acquire 

 the property of drying up more easily. 



IV. Magnesia. — Various opinions have been formed 

 of the action of magnesia on vegetation. Experiments 

 tried in many districts have shown that magnesia, in 

 combination with carbonic acid, as well as in its union 

 with silica, by no means exerts an unfavourable influence ; 

 on the contrary, thatit sometimes occurs in the most fertile 

 soils. — Einhof gives au example of a marl containing 20 

 t per cent, of carbonate of magnesia ; Sprengel, another 

 instance of a. marl, which contained even 28 per cent, of 

 this earth : while both these marls were employed with 

 as good an effect as others in which magnesia was not 

 present. The slaty marls of the keuper formation in 

 Wiirtemberg, which are frequently employed in vine- 

 cultivation, and often also as an under-dressing for [corn 

 crops, almost always containing carbonate of magnesia, the 

 proportion of which sometimes amounts to 30 per cent. 

 Berthier found magnesia in union with silica in the 

 fertile soils around Eille ; Burger gives an instance of 

 very fertile soils formed in Carinthia by the disinter- 

 gration -of serpentine and chlorite ; Davy also, in his 

 "Agricultural Chemistry," remarks, that the most fertile 

 districts of Cornwall abound in soils containing mild 

 magnesia. It appears, from these results of experience, 

 to be established, that this earth in combination with 

 carbonic acid, or in union with silica, is entirely un- 

 lujurious to vegetation ; it even further appears to act 

 beneficially on some plants as a means of nourishment, 

 as is the case, according to Sprengel, in the culture of 

 Flax, in the ashes of which plant especially, there is a 

 large portion of magnesia. The ashes of several other 

 plants also contain not unfrequently a certain amount 

 of this earth ; its presence however does not appear to 

 be absolutely necessary to any of them, since it occurs 

 m the ashes of the perfectly developed plants, in greater 

 and smaller quantities, or is even absent altogether, ac- 

 cording to the composition of the soils in which they 

 have been respectively grown, as has been particularly 

 noticed by Berthier in the ashes of the Oak. In its 

 fustic state magnesia is decidedly injurious to vegeta- 

 *j 0n ' Tennant first observed this effect in England, in 

 the cas e of a marl* which contained from 20 to 21 per 

 ^nt. of lime^ an( i f rom 29 to 31 per cent, of magnesia, 

 > ^on with carbonic acid). He endeavoured to explain 

 *~ action by the circumstances of the small affinity of 

 a gnesia for carbonic acid, and the longer time the 

 magnesia consequently required to become saturated 

 *™ that acid, than is the case with quicklime ; its 

 Presence thus, he thought, preventing the lime from 

 j*Coming so quickly saturated with carbonic acid as in 

 » simple state, without the magnesia, would have been 

 * e case. Experiments of my own on this point have 

 jJKewise confirmed the injurious effect of caustic mag- 

 ®a. ^ Corn, Peas, and garden-crops, which I sowed 

 P^ly in calcined magnesia previously moistened with 



and exposed to the air, 

 partly in earth merely mixed with calcined 

 j^^j either germinated not at all, or with a de- 

 jwped germen which soon became sickly, and the 

 ^ Un g plants soon died away ; while other seeds of 

 ^ same plants sown at the same time in pure 

 _ceous sand, carbonate of magnesia chrysolite, and 

 e r light insoluble powders, were, by similar treat- 

 sunder the same external circumstances, well deve- 



which came into contact with it acquired the character 

 of hydraulic mortar ; the earthy particles became har- 

 dened, even while in a thoroughly wet state (as another 

 series of experiments with this earth had previously 

 shown me) ; in consequence of which, the germ and 

 young plants could no longer develope themselves freely 

 in the soil ; even with a small admixture of calcined 



was this the case. The solubility which 



magnesia, 



water 

 and 



for 24 



•6 



hours 



magnesia, in its calcined state, possesses to a certain 

 extent, and the weak alkaline properties it consequently 

 exerts, may likewise contribute to this injurious effect. 

 Sprengel endeavoured to explain the injurious qualities j 

 of magnesia on vegetation, by the great solubility which 

 this earth exhibits, in combination with humic acid, as 

 humate of magnesia, and the too great amount of nou- 

 rishment which plants on that account absorbed, be- 

 coming injured in such case, as in every other, in which 

 the supply of rich pabulum is superabundant. This 

 may, under certain circumstances, be the case; but 

 from my own experiments, in which neither humus nor 

 humic acid came into play, calcined magnesia alone, and 

 of itself, clearly acted injuriously on young plants. We 

 cannot understand either, on this principle of explana- 

 tion, why carbonate of magnesia, in fertile soils contain- 

 ing humus, should not also frequently have a similar 

 injurious effect, since, in this case, humate of magnesia 

 must likewise be often formed. An experiment, too, of 

 Davy, is unfavourable to the explanation of Sprengel. 

 He remarks, that a soil containing much organic matter, 

 had a larger proportion ofc caustic magnesia in its com- 

 position than another soil, in which such was not the 

 case ; that peat, for instance, is an active and appropriate 

 corrective for soils that have previously suffered from 

 too great an application of magnesian limestone, in order 

 to again improve them, and even to convert them into 

 very fertile land. 



plied in large quantities to peats ; and that where lands have 

 been iojured by the application of too lar^e a quantity of 

 magnesian lime, peat will be a proper and efficient remedy. I 

 mentioned that magnesian Umestoues effervesced little when 

 pl.mged into an acid. A simple test of magnesia in a lime. 

 Btone is this circumstance, and its rendering diluted nitric 

 acid, or aquafortis, milky. From the analysis of Mr. Tennant, 

 it appears that the magnesian limestones contain from 20.3 to 

 22.5 of magnesia, from 29.5 to 31.7 of lime, 47.2 of carbonic 

 acid, and 0.8 of cJay and oxide of iron (per cent.). Magnesian 

 limestones are usually coloured brown or pale yellow. They 

 are found in Somersetshire, Leicestershire, Derbyshire, Shrop- 

 shire, Durham, and Yorkshire. I have never met with any in 

 other counties in England ; but they abound in many partB of 

 Ireland, particularly near Belfast." — Sir S. Davy's Seventh 

 Lecture. 



Oxides of Iron. — The peroxide of iron, like other 

 matter insoluble in water, appears frequently to remain 

 as an inert and indifferent ingredient of soil in refer- 

 ence to vegetation, when no strong acids exist in thef 

 soil, by which it may be dissolved ; a circumstance, 

 indeed, that very seldom occurs. In some experiment* 

 which I made on a small scale, plants developed them- 

 selves well in rich soils mixed with peroxide of iron, so 

 long as the soil possessed the other physical properties 



There are even soils on a 



favourable to vegetation, 

 large scale which 



not 



unfrequently are abundantly 

 fraught with this oxide, particularly in countries lying 

 on the keuper and lias-sandstone formations, like many 

 in South Germany, which belong to the most fertile dis- 

 tricts for orchards, vineyards, corn-fields, and the 

 growth of almost every kind of fruit. We might, 

 accordingly, be even tempted to ascribe to peroxide of 

 iron, individually, a particularly beneficial agency, 

 which, however, it does not appear to possess, at least 

 not. for many of the cultivated plants. ». There are no 

 less fertile tracts of land on the white Jura limestone^ 

 in districts of which the soils contain only inconsiderable 

 traces of that oxide ; although, at the same time, it is 

 not to be doubted that soils rich in the peroxide of iron 

 appear to be particularly favourable to certain plants, 

 as, for instance, to the Cinchona ferruginea in the 



Brazils. The protoxide of iron, on the other hand,. 



Magnesian Limestone (or Dolomite).—" The most consider- 

 able fact made known with regard to limestone, within the , - . . 

 few last years, is owing to Mr. Tennant. It had long: been appears to be ot less value than the peroxide tor vege- 



known that a particular species of limestone, found in j tation, as it more easily forms salts of iron injurious to 

 different parts of the north of England, when applied in its _ _ 



burnt and slacked state to land in considerable quantities, 

 occasioned sterility, or considerably injured the crops for many 

 years. Mr. Tennant, in 1800, by a chemical examination of 

 this species of limestone, ascertain* d that it differed from 

 common limestones by containing magnesian earth ; and by 

 several experiments he proved that this earth was prejudicial 

 to vegetation, when applied in large quantities in its caustic 

 state. Under common circumstances the lime from the 

 magnebian limestone is, however, used in moderate 

 quantities upon fertile soils, in Leicestershire, Derbyshire, 

 and Yorkshire, with good effect ; and it may be applied in 

 greater quantities to eoils containing very large proportions 

 of vegetable matter. Magnesia, when combined with 

 carbonic acid gas, 6eems not to be prejudicial to vegeta- 

 tion, and In soils rich in manure it is speedily supplied with 

 this principle from the decomposition of the manure."— Sir H. 

 Davy's Introd. Lecture. " The subject of the application of the 

 magnesian limestone is one of great interest. It had been 

 long known to farmers in the neighbourhood of Doneasur, 

 than lime made from a certain limestone applied to the land, 

 often injured the crops considerably. Mr. Tennaut, in making 

 a serieB of experiments upon this peculiar calcareous sub- 

 stance, found that it contained magnesia ; and on mixing 

 e erne calcined magnesia with soil, in which he sowed different 

 seeds, he found that they either died or vegetated in a very 

 imperfect manner, and the plants were never healthy. And 

 with great justice and ingenuity he referred the bad effects of 

 the peculiar lime&tone to the magnesian earth it contains. In 

 making some enquiries concerning this subject I Jouud that 

 there were cases in which tnis mbgnesiau limestone was u^ed 

 with good effect. Amongst some specimens of limestone wi ich 

 Lord Somerviile put into my hands, two marked as peculiar 1| 

 good proved to be magnesian limestones. And lime mace 

 from the Breedon limestone is used in Leicestershire, where 

 it is called 'hot lime f and I have been infornud by farmers 

 in the neighbourhood of the quarry, that they employ it 

 advantageously in small quantities, seldom more than 25 or 



00 bushels to the acre. And that ihey find it may be used with 

 good effect in larger quantities upon rich land. A minute 

 chemical consideration of this question will lead to its solution. 

 Magnesia has a much weaker attraction for carbonic acid than 

 lime, and will remain in the state of caustic, or calcined, 

 magnesia for many months, though exposed to the air. Ani 

 as long as any caustic lime remains, the maguesia cannot be 

 combined with carbonic acid, for lime instantly attracts cai- 

 bonic acid from magnesia. When a magnesian limestone is 

 burnt, the magnesia is deprived of carbonic acid much sooner 

 than the lime ; and if there is not much vegetable or animal 

 matter in the soil to supply by its decomposition carbonic acid, 

 the magnesia will remain for a long while in the caustic 

 state ; and in this state acts as a poison to certain vege- 

 tables. And that more magnesian lime may be used upou 

 rich soils seems to be owing to the circumstance, that the de- 

 composition of the manure in them supplies carbonic acid. 

 And magnesia in its mild state (that is, fully combined with 

 carbonic acid) seems to be always an use'ul c nstituent of 

 soil*. I have thrown carbonate of magnesia (procured by 

 boiling the solution of magnesia in super-car bona* e uf potash) 

 upon Grass and upon growing Wheat and Barley, so as to 

 render the surface whi^e, but the vegetation was not injured 

 in the slightest degree. And one of the most fertile parts of 

 Cornwall, the Lizard, is a district in which the I 1 contains 

 mild magnesian earth. The Lizard Dow Hi bear a short and green 

 Gra«s, which feeds sheep producing excellent mutton ; and the 

 cultivated parts are among the best corn-lands in tke county. 

 That the theory which I have ventured to give of theoperatiou ol 

 magnesian lime is not unfouuded, is shown by an experiment I 

 made expressly for the purpose of determining the true nature of 

 the operation of this substauce. I took four portions ot the same 

 soil; with one I mixed one-twentieth of its w\U lit oi caustic 

 magnesia, with another I mixed the same quantity of mag- 

 nesia and a proportion of a fat decomposing peat equal to one- 

 fourth of the weight of the soil : one portion of soil remained 

 in its natural state, and another was mixed with peat with- 

 out magnesia. The mixtures were made iu Ducemb. , 1306 ; 

 aud in April, 1807, Barley was sown in all of them. It grew 

 very well in the pure soi', but better in the soil conta ; ninK 

 the magnesia and peat, and nearly as well in the soil 

 containing peat alone ; but in the soil containing the mag- 

 nesia alone, it rose very it- e'ole, and looked yellow and sickly. 



1 repeated this experiment in the summer of 1810, with si; ar 

 results, and I found that the magnesia iu the soil mixed with 

 peat became strong ; y efferresc nt, whilst the portion in 

 the unmixed soil gave carbonic acid in much smalk 

 quantities. In the one case, the magnesia had as>Uted in the 

 formation of a manure, and had become mild; in the other 



plants ; and also, from its imperfectly oxidised state, is 

 more likely to abstract oxygen from the surrounding 

 soil, and from the roots of plants ramifying themselves 

 throughout it. The marls, which contain much pro- 

 toxide of iron, often become on this account only bene-* 

 ficial in their action after they have been exposed to the 

 atmosphere for some time previous to their application » 

 Chaptal adduces some observations on lands which, in 

 consequence of the ploughing up of the black protoxide 

 of iron, remained sterile for some years, but which after- 

 wards attained a high degree of fertility on the saturation 

 of* the soil with oxygen ; a result that in one case was ac* 

 companied with a change of colour in the soil from adingy • 

 brown to a deep yellow. The beneficial effect of turf-burn- 

 ing in the cultivation of peat lands appears also, at least* 

 in part, to rest on the same cause ; as the protoxide of 

 iron, which not unfrequently occurs in such land, is by 

 this operation more speedily converted into the peroxide; 

 The well-known fact, that the Hortensia speciosa, so 

 frequently cultivated as an ornamental plant, developes 

 blue flowers, instead of its ordinary red ones, when it is 

 planted in soils which are rich in protoxide of iron and 

 fine carbonaceous particles, or which contain the latter 

 only, indicates, in a particular manner, that such imper- 

 fectly oxidised bodies^may even exert deoxidising effects 

 on the plants grown in them. These artificially blue- 

 flowered Hortensias become as ordinarily red when 

 their petals are only touched lightly with a weak acid, 

 a clear proof that this blue colour had not been occa- 

 sioned solely by absorbed particles of charcoal or prot- 

 oxide of iron, as had been already assumed. We should, 

 moreover, greatly err in regarding soils which contain- 

 protoxide of iron as being generally injurious to vege- 

 tation. I found various plants develope themselves well 

 in soils to which I had added several per-centages of 

 pure protoxide of iron. Soils of great extent, too,- not 

 unfrequently occur, containing that protoxide, without 

 its being known to exert an injurious influence on vege- 

 tation. Such oils appear on the grounds already 

 stated, only to be capable of assuming, under certain 

 external circumstances, more easily than other soil% 

 these properties which are injurious to vegetation. 



Oxide of Manganese. — A& this metallic oxide does 

 not commonly occur in soils free, but combined with 

 earths and peroxide of iron in an almost insoluble state, it 

 appeal^ frequently to remain as an indifferent and inert 

 ingredient of soil ; and I found by artificial mixture of 

 it in large proportions -with soil, to be uninjurious. 

 Sprengel found in the Waldeck a marl containing 4 

 cent, of oxide of manganese, which was applied with 

 great advantage to the improvement of the Grass-lands. 

 Its amount, moreover, is very various in the ashes of 

 plants ; and in the case of the same plant, even at its 

 perfect development, it does not occur constantly in the 

 same proportion. It would appear that it must be 

 classed rather with the accidental ingredients of the soil 

 than with those component parts of it which are essen- 

 tially necessary for vegetation. 



iim 



w 



lar? 



Home Correspondence. 



Thatch [vtrsusl pe'rmanent Shelter. — When a 

 stock is kept through the winter, economy in the use of 

 straw is requisite. The quantity required for thatching, 

 first the hay-ricks and then the corn, is considerable ; 

 and this at a period at which the stock of straw usually 

 runs short. Ac;ain, the annual expense of thatching a 

 large number of ricks is great. Furthermore, several 



