20 The Eothamsted Wheat Experiments. 



selected cases been determined. The percentage of nitrogen 

 in the soil of some of the plots, at different stages of the 

 progress of the experiments, has also been estimated. 



One useful result of a study of the Rothamsted experi- 

 ments is that intending investigators may learn, not only 

 what methods are best to follow, but those which it is 

 desirable to avoid. As already mentioned, these wheat- 

 growing experiments were not during the first eight years 

 carried out with uniformity of manuring on each plot. 

 Referring to this point, the experimenters observe, in the 

 introduction to their second report, that an attempt to inves- 

 tigate the growth of wheat, under circumstances so totally 

 different from any which had ever previously arisen, could 

 hardly be carried out without the commission of some errors 

 which experience would have enabled them to avoid. They 

 have now ascertained that, if it is desired to advance beyond 

 the question of the best manure to grow one crop of wheat, 

 continuity of the same manuring is of supreme importance. 

 With the exception of the plot receiving farmyard dung, and 

 the unmanured plot neither of which has been altered from 

 the commencement there is no plot in the field in which some 

 change did not take place in the manure applied during the 

 early years of the experiments. But in the autumn of 1851, 

 eight years after the experiments were commenced, the 

 manuring of the field was arranged upon a fixed plan which, 

 with very slight changes in one or two instances, has been 

 followed ever since. 



As, therefore, the manurial treatment of each plot has, 

 since 1852, not been varied, it will be convenient to state 

 here, once for all, the description and quantities, estimated 

 per acre per annum, of the several manures : 



Plot 2. 14 tons farmyard manure (also for the eight preceding years). 

 Plot 3. Unmanured (also for the eight preceding years). 

 Plot 20. Unmanured (also for five preceding years). 

 Plot 4. Unmanured (sulphate of ammonia and bone ash acted upon by 

 hydrochloric acid, for seven preceding years). 



