FARMERS" REGISTER— CAUSE OF GYPSUM NOT ACTING. 



633 



[V limestone soil, to our surprise, these specimens 

 wlien treated with muriatic acid, gave no indica- 

 tion of calcareous earth; and on procurino; others 

 from a dark rich loam amongst broken limestone 

 partly disintegrated, the elicrvescence was but 

 barely visible. On digging down into the subsoil 

 liowever, and subjecting a specimen to tlie same 

 treatment, the carbonic acid t()anied in the glass. 

 We are tiierelbrc jirepared to adopt liie conclusion 

 of our author, thai calcareous matter when mixed 

 witli the soil, soon becomes converted into the 

 oxalate of lime* and the unchanged stale ot" thai 

 subsoil, fi'om not having been penetrated by the 

 vegetable acids, may be otlered as additional evi- 

 dence. 



lie has not left this opinion however, unsupport- 

 etl by direct experiments. To an acid soil, full ol 

 vegetable matter, he applied fossil shells at such a 

 known and heavy rate as would have given to the 

 soil (by calculation) at least three per cent, of cal- 

 careous earth to the depth of live inches. Aller the 

 field had been cullivateil six j-ears, the soil was 

 examined; and in the first experiment 1000 grains 

 only yielded eight of calcareous matter; the second 

 experiment only seven graiiis; and in the thiril, 

 1500 grains produced seventeen and a half. The 

 average is thus consideraijlj- less than one percent.; 

 and shows that more than two per cent, of calca- 

 reous matter had undergone a new combina- 

 tion. 



As a sample of our author's manner of treating 

 a subject, avc select a "Note" in the appendix on 

 the application of gypsum. In the lower parts of 

 Pennsylvania, liming has been Ibund to insure the 

 efficacy of that wonderful numure; and some of 

 our readers may recollect that our correspondent 

 J. Spicer (Vol. 2, p. 165,) has derived great bene- 

 fit from mixing ashes with it before sowing. How 

 these operate, we think the "Note" (which follows) 

 will satisfactorily explain. 



"I do not pretend to explain the mode of opera- 

 tion bj^ which gypsum |)roduccs its almost magic 

 benefits: it would be equally hopeless and ridicu- 

 lous lor one having so little knowledge of the suc- 

 cessful practice, to attempt an explanation, in 

 which so man}- good chemists, and agriculturists 

 both scientific and ])ractical, have completely fail- 

 ed. There is no operation of nature heretofore 

 less understood, or of which the cause, or agent, 

 seems so totally disproportioned to theetfect, as the 

 enormous increase of", vegetable growth fi'om a 

 very small quantity of gypsum, in circumstances 

 favorable to its action. All other known manures, 

 whatever may be the nature of their action, re- 

 (juire to be a])|)lied in quantities, very fiir exceed- 

 ing any bulk oi' crop expected from their use. But 

 one bushel of gypsum, spread over an acre of 

 land fit for its action, may add more than twent}- 

 times its owiijveight to a single crop of clover. 



"Howevervvonderful and inscrutable the fertil- 

 izing power of this manure may be, and admitting 

 its cause as yet to be hidden, and entirely beyond 



* This accords with the assertion of the Earl of 

 Dundonald in his Connexion of ./Is^ricnltiu e and Chem- 

 istry: "Much of the oxalate of lime will be formed by 

 adding calcareous matter to i;i'ound abounding witli 

 plants of sorrel or other vegetables containing the 

 sorreline or oxalic acid." He has referred to no ex- 

 periments however, in proof of this opinion. Gen. Far. 



Vol. 11—16 



I our reach — still it is possible to show reasons why 

 gyj)sum cannot act on many situations, where all 

 experience has ))roved it to be worthless. If this 

 only can be satisliictorily explained, it will remove 

 nmch of the uncertainty as to the cllects to be ex- 

 pected: and the farmer may thence learn on what 

 soils he may hope lor benefit li^om this manure — 

 on what it will certainlj' be thrown away — and by 

 what means the circumstances adverse to its ac- 

 tion may be removed, and its efficacy tliereby se- 

 cured. This is the cxiilanation that I shail at- 

 temjit. 



'•if the vegetable acid, which I suppose to exist 

 in what I have called acid soils, is not the oxalic, 

 (which is the particular acid in sorrel,) at least 

 every vegetable acid, being composed ol diiierent 

 proportions ol" the same elements, may easily 

 change to anj- other, and all to the oxalic acid. 

 This, of all bodies known by chemists, has the 

 strongest attraction for lime, and will take it from 

 any other acid which was belbre combined vvhh it 

 — and for Lhat purpose, the oxalic acid will let go 

 any other earth or metal, which it had before held 

 in combination. Let us then observe what would 

 be the eliect of the known chemical action of these 

 substances, on their nieetin,:^ in soils. If" oxalic 

 acid was produced in any soil, its immediate effect 

 would be to unite with its proi)er proportion ol lime, 

 if enough was in the soil in any combination what- 

 ever. If the lime was in such small quantity a."? 

 to leave an excess of oxalic acid, that excess would 

 seize on the other substances in the soil, in the or- 

 der of their mutual attractive force; and one or 

 more of such substances are always present, as 

 magnesia, or more certainly, iron and alumina. 

 The soil then would not only contain some propor- 

 tion of the oxalate cf lime, but also the oxalate of 

 either one or more of the other substances named. 

 Let us suppose gypsum to be applied to this soil. 

 This substance, (sulphate of lime) is composed of 

 sulphuric acid and lime. It is a])plied in a finely 

 |)ulverized state, and in quanthies from half a 

 bushel to two bushels the acre — generally not 

 more than one bushel. As soon as the earth is 

 made wet enough for any chemical decoin|)osition 

 to take place, the oxalic acid must let go its base of 

 iron, or alumina, and seize upon and combine whh 

 the lime that tbrmed an ingredient of the gyj)sum. 

 The sulphuric acid left t"ree, will combine with the 

 iron, or the alumina of the soil, forming copperas 

 in the one case, and alum in the other. The gyp- 

 Sinn no longer exists — and surely no more satisfac- 

 tory reason can be given Vvdiy no efiect from it 

 should follow. Thedecomposition of the gypsum 

 has served to form two or [)erhaps three other sub- 

 stances. One of them, oxalate of lime, I suppose 

 to be highly valuable as rnaimre: but the very 

 small quantity that could be formed out of one or 

 even two bushels of gy|isum, could have no more 

 visible en<?ct on a whole acre, than that small 

 quantity of cidcareous earth, or farm-yard manure. 

 The other substance certainly formed, copperas, is 

 known to be a poison to soil and to plants — and 

 alum, of which the formation would be doubtful, I 

 believe is also hurtful. In such small quantities, 

 however, the poison would be as little perceptible 

 as the manure — and no apparent efiect whatever 

 could follow such an ajiplication of gypsum to an 

 acid soil. So small a proportion of oxalic acid, or 

 any oxalate other than of lime^ would suffice to 

 decompose and destroy the gypsum, thtit it v.-ould 



