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XVIII. — Afjricultural Chemistry. — On the Grototh of Barley hy 

 different Manures, continuously on the same Land; and on the 

 position of the Crop in Rotation. By J. B. Lawes, F.E.S., F.C.S., 

 and Dr. J. H. Gilbert, F.C.S. 



In endeavouring in former Papers in this Journal to convey such 

 an idea as existing knowledge permitted, of the chemical facts and 

 principles which our Rotation of Crojjs involves, w^e have supported 

 the views put forth, by carefully ascertained data regarding the 

 individual elements which constitute that important practice. 

 The subjects which necessarily pass under review in such an 

 inquiry are, the characteristic requirements of growth of — 



1st. The Root Crops, 



2nd. The saleable Cereal Grains, 



3rd, The Leguminous Corn and Fodder Crops ; 

 and lastly, the chemical circumstances involved in— 



4th. The consumption of food by stock on the farm. 



In regard to some of these branches, only the general conclu- 

 sions drawn from the evidence accumulated have been given ; 

 whilst on others, a good deal of the evidence upon Avhich the con- 

 clusions have been founded, has, been laid in detail before the 

 reader. 



Thus, with regard to the Cereals, the reader is already in pos- 

 session of a considerable portion of the results of the experiments 

 in the field ^ relating to the growth of wheat ; and before adding 

 to the registry on that head, it seems desirable to put on record 

 something relating to harley — the next in importance to wheat in 

 the class of the saleable cereal grains of our rotations. 



We have always assumed that barley, apart from local and 

 minor distinctions, was closely allied to wheat in certain cha- 

 racteristic chemical requirements of its growth. Independently 

 of common observation, the direct evidence upon which this 

 opinion was founded, was a course of field experiments on barley, 

 conducted in 1845. At that time about ten acres were appro- 

 priated to the investigation, which it was intended should be 

 continued through a considerable series of years. Owing, how- 

 ever, to the great labour and attention required in following up 

 experiments of this kind, both in field and laboratory, with suffi- 

 cient accuracy and detail to serve a scientific purpose, it was 

 decided to rest satisfied with the first year's clear indications in 

 the field, until other branches of the main inquiry, then occupying 

 all our available time, should be somewhat further forwarded. 



* For the results in the laboratory, showing the influence of circumstances of 

 growth on the composition of wheat, see ' Journal of the Chemical Society,' vol. x., 

 part i., p. 1-55 : ' On some points in the Composition of Wheat-Grain, its 

 Products in the Mill, and Bread.' 



