INTRODUCTION. 1 7 



some of the most interesting and the most valuable of our results, 

 as will be fully illustrated as we proceed. 



Table I. further shows the area, and the number of plots, 

 under experiment in each case ; and it may be stated that the 

 total area under exact and continuous experiment has been for 

 some years, and is at the present time, about 40 acres. 



The next point to consider is — What is the most appropriate 

 selection to make among the field and other results ; and what 

 is the most appropriate order in which to consider them, in 

 attempting to illustrate the objects, plan, and results, of the 

 Eothamsted investigations ? It will be readily understood that 

 our selection of crops for investigation was largely influenced 

 by the actual practice of our own part of the country. The 

 separately grown individual crops were, in fact, the chief of 

 those entering into our rotations ; whilst the rotation selected 

 for study was the well-known " four course " — namely, roots, 

 barley, leguminous crop (or fallow), and wheat. Obviously, 

 therefore, the most natural order of illustration would be that 

 indicated by the ideas and conditions in accordance with which 

 the experiments have been arranged and conducted; and the 

 order so indicated will, we think, be found to be, upon the 

 whole, not only the most convenient but the most instructive. 



We have, it is true, in different parts of the country a great 

 variety of soil and of climate, and accordingly great variety in 

 crops, and in the order of their rotation. Still, it will be seen 

 that the selection of individual crops experimented upon in- 

 cludes most, and certainly the most typical, of those grown in 

 the varied rotations of different parts of the country ; and it will 

 be admitted that, in some important respects, the characteristic 

 requirements of the individual crops are very similar whether 

 grown in one locality or in another. Indeed, it cannot fail to 

 be recognised that, mutatis mutandis, the results which have 

 been obtained under given conditions at Eothamsted are not 

 without their significance and bearing, under the different con- 

 ditions of other localities. 



In accordance with what has been said, it is proposed to 

 consider the results obtained, with the selection of the crops 

 experimentally grown, and in the laboratory investigations con- 

 nected with them, as given in the following list. Lastly, it will 

 be seen that the very important complementary subject of the 

 feeding of animals will also be considered. 



1. Eoot-crops — Common turnips, Swedish turnips, sugar- 



beet, and mangel-wurzel ; each grown continuously. 



2. Barley — grown continuously. 



3. Leguminous crops — Clover, beans, and various other Le- 



gummosa? ; mostly grown continuously. Also the 

 question of the fixation of free nitrogen. 



VOL. VII. B 



