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On Agricultural Chemistrij. 



obtaining ammonia ; but as the amount obtained by green crops 

 must depend very much upon their bulk, every attention should 

 be paid to their growth. In order to produce the great- 

 est weight of turnips, it is necessary that the soil should be 

 brought to the finest and lightest condition possible by mechani- 

 cal means, and that it should be manured by a large and available 

 supply of carbon and phosphates. Ammonia artificially supplied 

 is not essential if the soil be not deficient in carbonaceous sub- 

 stances ; and where the phosphates are not supplied in sufficient 

 quantity it exerts a most injurious effect upon the plant. 



The turnip is essentially a plant which requires artificial aid 

 for its development in agricultural quality and quantity. It is 

 singular that while my soil yields 17 bushels of wheat annually, 

 without manure, the turnips upon an unmanured space were re- 

 duced to a few cwt. per acre in three years, and in the fourth 

 only averaged the size of a radish. It is also remarkable that a 

 plant whose office it is to restore fertility to the soil should 

 scarcely be able to exist where wheat was yielding a tolerable 

 crop ; but the different effect produced upon two crops by farm- 

 yard dung and superphosphate of lime at once explains this 

 anomaly. Eighty-four tons of farm-yard dung, consisting of de- 

 caying straw mixed with the excrement of the farm-horses, ap})lied 

 to one acre of wheat and one of turnips during three years, at the 

 rate of 14 tons per acre per annum, did not, in the acre of wheat, 

 add much more than one-half to the natural produce each year: 

 the turnips, however, were increased to an indefinite extent. 

 Superphosphate of lime, which produced no increase of wheat the 

 first year it was applied, gave in succession three good crops of 

 turnips. The dung which I applied to my wheat increased the 

 produce to an extent equivalent to the amount of ammonia which 

 it may be estimated to contain ; but it is evident that the great 

 bulk of 42 tons served little useful purpose, for we find that 

 salts of ammonia have produced each year a larger amount of 

 corn. The whole of the solid matter of the residue, consisting of 

 organic matter almost destitute of nitrogen, could have been 

 assimilated by the turnip, under the influence of a due supply of 

 phosphates. On poor soils it is quite consistent with scientific 

 principles to employ rich azotized dung for the wheat crop, and 

 to convert the carbonaceous residue into the substance of the 

 turnip by an abundance of phosphates. It would, however, pro- 

 bably be advantageous to have a greater proportion than one- 

 fourth of the farm under turnips each year. At present, upon 

 the Norfolk system one-fourth of the farm is clover, but broad 

 clover cannot be obtained with certainty so often. If instead of 

 this, one-eighth of a farm was clover and three-eighths turnips, 

 a larger proportion of winter food would be obtained, and as 



