22 The Eothamsted Wheat Experiments. 



Plot 96. 5501b. nitrate of soda alone (only 4751b. in the ninth season). 



Plot 15a. Mixed mineral manure as plots 5 (but with 2001b. hydro- 

 chloric instead of 1501b. sulphuric acid), and 4001b. sulphate of ammonia. 



Plot 156. Mixed mineral manure as plots 5 (but with 2001b. hydro- 

 chloric instead of 1501b. sulphuric acid), 3001b. sulphate of ammonia, and 

 5001b. rape cake. 



Plot 19. 2001b. bone ash, 2001b. hydrochloric acid, 3001b. sulphate of 

 ammonia, and 5001b. rape cake. 



The sulphates of potash, soda, and ammonia, the muriate 

 (chloride) of ammonia, and the nitrate of soda, were the 

 ordinary articles of commerce passing under those names ; the 

 sulphate of magnesia was Epsom salts. The term " ammonia- 

 salts " may for brevity be employed to denote the mixture of 

 equal quantities of sulphate and muriate of ammonia. 



The 14-acre field set apart for the experiments had, at the 

 commencement of the investigations, grown turnips, barley,. 

 peas, wheat, and oats since the application of manure, and 

 would therefore, according to the ordinary rules of practice, 

 be considered so far exhausted as to need re-manuring before 

 growing another crop. It was considered that a field in this 

 condition would be peculiarly fitted to show in which of the 

 constituents of the crop to be grown the soil had become 

 practically the most deficient by the removal in rotation of 

 the five preceding crops just enumerated. It was felt by the 

 experimenters at the outset that far more had yet to be done 

 in determining the chemical and physical qualities of soils in 

 relation to the atmosphere, and to manurial substances 

 exposed to their action, as well as in perfecting methods of 

 analysis, before comparative analyses could aid much in 

 deciding upon the relative productiveness of different soils r 

 to say nothing of the still more difficult problem of estimat- 

 ing by such means the condition of fertility or exhaustion of 

 one and the same soil at different times. The field was at 

 first divided into plots, of which most consisted of two lands 

 (each about 12ft. 5in. wide), running the whole length of 

 the field, and comprising altogether nearly two-thirds of an 

 acre. After the second season, however, the double land plots 



