27 



corresponding to those in which nitrogen has been 

 determined. 



Soil samples were taken from a selection of plots, 

 in 1857 to a depth of 9 inches, in 1865 to the depth of 

 3 times 9, or 27 inches, in 18 74 to the depth of 9 inches, 

 in 1883 to the depth of 8 times 9 inches, and in 1885 

 to the depth of 9 inches only. The nitrogen by soda- 

 lime has been determined, in mixed samples for each 

 selected plot and depth, and in some individual 

 samples ; and in some the nitrogen as nitric acid has 

 also been determined. 



Some of the results have been given in No. 67 ; but 

 more, though still only in summary, in their bearing 

 on the question of the sources of the nitrogen of vege- 

 tation, in the paper in the " Philosophical Transactions" 

 numbered 77 in the list, The results have, however, 

 been published more fully, so far as they relate to 

 the amounts of produce of the bean and clover crops, 

 and to the nitrogen in them, in No. 81. 



It may be added, that after the removal of the clover 

 crops, and the final soil sampling in 1885, the portion 

 of the field that had been under continuous bean crops 

 was fenced off to exclude cattle from it, and it has been 

 left uncultivated ever since. A luxuriant growth of 

 grasses, and other herbage, soon established itself, and 

 this has been left to seed, with the object of ascertain- 

 ing to what extent the soil will acquire fertility under 

 the influence of the undisturbed natural perennial vege- 

 tation. It is doubtful whether it will be worth while to 

 sample the soil at the end of 10 years, that is in 1895, 

 and it may be desirable to let the experiment go on for 

 at least 20 years, and perhaps longer; but the soil 

 should certainly be sampled at the expiration of 

 20 years, and again at the termination of the experi- 

 ment if it be continued longer. It should be observed 

 that this portion of land has not been conveyed to the 

 Trustees, but Sir J. B. Lawes leaves a memorandum 

 expressing his wish that the land shall remain at the 

 disposal of the Committee so long as they desire to 

 carry on the experiment. 





