PROCEEDINGS 



OF 



THE ROYAL SOCIETY. 



1845. No. 61. 



May 22, 1845. 



The MARQUIS OF NORTHAMPTON, President, in the Chair. 



" Memoir on the Rotation of Crops, and on the Quantity of In- 

 organic Matters abstracted from the Soil by various plants under 

 different circumstances." By Charles G. B. Daubeny, M.D., F.R.S., 

 Professor of Rural Economy, &c. in the University of Oxford. 



The author was first led to undertake the researches of which an 

 account is given in the present memoir, by the expectation of verify- 

 ing the theory of DeCandoUe, in which the deterioration experienced 

 by most crops on their repetition was attributed to the deleterious 

 influence of their root- excretions. For this purpose he set apart, 

 ten years ago, a number of plots of ground in the Botanic Garden 

 at Oxford; uniform as to quality and richness, one-half of which 

 was planted each year, up to the present time, with the same species 

 of crop, and the other half with the vsame kinds, succeeding each 

 other in such a manner that no one plot should receive the same 

 crop twice during the time of the continuance of the experiments, 

 or at least not within a short period of one another. The difference 

 in the produce obtained in the two crops, under these circumstances, 

 would, the author conceived, represent the degree of influence 

 ascribable to the root-excretions. 



The results obtained during the first few years from these experi- 

 ments, as well as from the researches which had, in the mean time, 

 been communicated to the world by M. Braconnot and others on 

 the same subject, led him in a great measure to abandon this theory, 

 and to seek for some other mode of explaining the falling-off' of crops 

 on repetition. In order to clear up the matter, he determined to 

 ascertain, for a series of years, not only the amount of crop which 

 would be obtained from each of the plants tried under these two 

 systems, but also the quantity of inorganic matters extracted in each 

 case from the soil, and the chemical constitution of the latter, which 

 had furnished these ingredients. The chemical examination of the 

 crops, hov/ever, on account of the labour it involved, was confined 

 to six out of the number of the plants cultivated ; and of these, three 



