150 GYPSUM MADE ACTIVE ON MARLED LAND. 



[Since the publication of the foregoing part of this chapter, in 

 the edition of 1832, my use of g} 7 psum, on land formerly .acid, has 

 been more extended, and the results have been such as to give ad- 

 ditional confidence in the practice, and, indeed, an assurance of 

 good profit, on the average of such applications. But still, as be- 

 fore, disappointments, either total or nearly so, in the effect of such 

 applications, have sometimes occurred, and without there being 

 any known or apparent cause to which to attribute such disappoint- 

 ment in the results. 



In 1832, nine acres of the same body of ridge land above re- 

 ferred to, adjoining the piece on which the 1st, 2d, 3d, and 4th 

 experiments were made, and more lately cleared, were sown in 

 clover in the early part of 1831, on wheat. The next spring, 

 French gypsum was sown at the rate of a bushel to the acre, ex- 

 cept on four marked adjoining squares, each about one-third of an 

 acre, one of which was left without gypsum, and the others received 

 it at the several rates of 2, 3, and 4 bushels to the acre. The 

 whole brought a middling crop, and was mowed for hay, except the 

 square left without gypsum, which did not produce more than half 

 as much as the adjoining land where gypsum was applied at one 

 bushel the acre. The products of the other pieces were slightly 

 increased by each addition to the gypsum, but by no means in 

 proportion to the increased quantity used j nor was the effect of the 

 four bushels near equal to that formerly obtained, in several cases, 

 from 20 bushels of gypseous earth taken from the river bank. 

 Hence it seems that it was not merely the unusual quantity of 

 gypsum applied in this earth, which produced such remarkable 

 benefit ; and we must infer that it contains some other quality or 

 ingredient capable of giving additional improvement to clover. 

 1835.] 



[Since the first publication of the foregoing passage (in 1835), 

 and in accordance with the views there presented, more than 10 

 tons of good French gypsum has been used, in different years and 

 with less effect, in general, than formerly, in the first few years 

 after the marling. This general diminution, and more frequent 

 total failures, may be owing to the longer time that the land has 

 been marled, and, by the increase of its vegetable supplies serving 

 as putrescent manure, the land being thereby changed from calca- 

 reous to neutral, and perhaps in some cases even approaching again 

 to being acid. If this supposition be well founded, then a repetition 

 of the marling would not only be profitable in other respects, but 



apply gypsum for favouring the clover crop, since the lime, in decomposing 

 the sulphates, has already formed an abundant supply of this compound 

 for all the purposes of vegetation." Lectures on Agr. Chein. p. 414.] 



