102 CALCAElvOUS MANL'UIlS-PKAGIICE. 



to injure land of certain qualities, it seemed to i^e a fair deduction, that the 

 benefit expected from so heavy a dressing, might have been obtained from 

 half the quantity — if not on the first crop, at least on every one afterwards. 

 That surely is nothing to be lamented. It also aflbrded some consolation 

 for the evil of the too heavy marlings already applied, that the soil was 

 tiiereby fitted to seize upon and retain a greater quantity of vegetable mat- 

 ter, and would thereby ultimately reach a higher grade of fertility. 



The cause of this disease is less apparent than its remedies. It is certain 

 that it is not produced merely by the quantity of calcareous earth in the 

 soil. If it were so, similar effects, shown in diseased crops, would always 

 be found on soils containing far greater proportions of that earth. These 

 injurious effects have not been known, to any extent, except on soils for- 

 merly acid, and made calcareous artificially ; and not on either neutral or 

 calcareous soils, even by the addition of a great excess of marl. The small 

 spots of land that nature has made excessively calcareous, and also sandy 

 by marl beds cropping out at the surface of cultivated fields, (as the speci- 

 men 4, page 38,) produce indeed a pale feeble growth of corn, such as might 

 be expected from poor gravelly soils— but whether the plants yield grain, or 

 are barren, they show none of those peculiar and strongly marked symp- 

 toms of disease which have been described. Some such places on my farm, 

 from which great quantities of poor sandy marl had been removed for ma- 

 nure, and where the remainder still was of unknown depth, have been after- 

 wards cultivated with the surrounding land; and with no more aid than the 

 portion of the adjacent soil carried thereto necessarily by the plough, these 

 places have gradually improved to a product equal to 12 or 15 bushels of 

 corn per acre, and have never exhibited any mark of the marl disease, 



By calculation, it appears that the heaviest dressing causing injurious 

 consequences, if mixed to the depth of five inches, has not given to the soil 

 a proportion of calcareous earth equal to two per cent. This proportion .is 

 greatly exceeded in our best shelly land, and no such disease is found there, 

 even when the rich mould is nearly all washed away, and the shells mostly 

 left. Soils of remarkable fertility from the prairies of Alabama and Missis- 

 sippi have been shown (page 43) to contain from 8 to 16 per cent, of calca- 

 reous earth, all of which proportions were in the state of most minute divi- 

 sion, and therefore most ready to produce this disease, if it could have been 

 produced by the quantity of this ingredient. The soil of the borders of 

 the Nile, celebrated for its exuberant fertility through thousands of succes- 

 sive crops, contains about 25 per cent, of carbonate of lime. (LyeWs 

 Geology.) Very fertile soils in France and England sometimes contain 20 

 or 30 per cent. Among the soils of remarkable good qualities analyzed 

 by Davy, one is stated ta contain about 28 per cent., and another, which 

 was eight-ninths of silicious sand, contained nearly 1 per cent, of calca- 

 reous earth. Nor does he intimate that such proportions are very rare. 

 Siniilar results have been stated, from analyses reported by Kirwan, Young, 

 Bergman, and Rozier, (page 32,) and from all the same deduction is. inevi- 

 table, that much larger natural proportions of calcareous earth, than our 

 diseased lands have received, are very common in France and England, 

 without any such effect being produced. 



From the numerous facts of which these are examples, it is certain that 

 calcareous earth acting alone, or directly, has not caused this injury ; and 

 it seems most probable that the cause is some new combination of lime 

 formed in acid soils only ; and that this new combination is hurtful to grain 

 under certain circumstances, which we may avoid, and is highly beneficial 

 to every kind of clover. Perhaps it is the salt of lime, formed by the calca- 

 reous manure combining with the acid of the soil, which not meeting with 



