218 THE HOTHAMSTED EXPERIMENTS. 



The Amounts of Pkoduce grown in Eotation, and in 

 the various crops grown continuously. 



Obviously, when considering what are the benefits arising 

 from rotation as distinguished from the growth of the indi- 

 vidual crops continuously, it is desirable, as far as practicable, 

 to compare the results of the two methods in regard to their 

 yield per acre of some of the more important constituents of 

 the crops. For the purposes of such a comparison, it will be 

 of interest to illustrate the point by reference specially to the 

 amounts of dry matter, nitrogen, total mineral matter (ash), 

 phosphoric acid, and potash (and in some cases of lime), in 

 the crops grown in rotation, and in those grown continuously, 

 under as far as possible parallel conditions as to manuring. 

 Methods of Accordingly, so far as results obtained under rotation are 

 Honex?' concerne d> the amounts of each of the above constituents are 

 plained. calculated in the produce per acre of the respective crops, in 

 • each of the eight courses (second to ninth), under each of the 

 twelve different conditions as to manuring, or other treat- 

 ment ; and the average amounts of these per acre per annum 

 are compared with those in the individual crops grown con- 

 tinuously, as a rule in the same seasons as those in which 

 the rotation crops were obtained, and under the same, or 

 nearly parallel, conditions as to manuring. 



The amounts of the constituents removed per acre in the 

 rotation crops are calculated from the results of actual an- 

 alyses ; and in the case of the continuously grown crops the 

 amounts of dry matter and ash, and sometimes those of nitro- 

 gen, are also calculated from direct determinations ; but 

 generally the nitrogen, and always the phosphoric acid, 

 potash, and lime, are calculated from the percentage compo- 

 sition of the rotation crops grown under parallel conditions 

 as to manuring. It may be stated that, for the purposes of 

 the illustrations given, the results of 60 complete analyses of 

 the ashes of representative samples of the rotation crops, and 

 of 8 of the ashes of the bean plant taken at different stages 

 of its growth, have thus contributed ; and it may be added, 

 that the ash-analyses were executed by Mr E. Eichter, for- 

 merly in the Eothamsted Laboratory, but now for some years 

 of Charlottenburg, Berlin. 



The Amounts of Dry Matter produced in the Rotation, 

 and in the Continuous Crops. 



Table 60 (p. 219) shows the average annual amount of dry 

 ■matter produced per acre, in each of the four crops — roots, 

 barley, leguminous crop, and wheat — grown in rotation, and 



