i8 



TABLE VIII. 



Wheat year after year on the same land. Broadbalk Field, Eothamsted. 



Produce of the best season, 1863 ; the worst season, 1879 ; and 

 average of 32 years, 1852-1883. 



We will confine our attention to the amount of dressed grain per acre 

 in bushels. The difference in yield of the various plots in the best and 

 worst of the thirty-two seasons is very marked. The unmanured, the 

 mineral manured, and the heavily nitrogeneous manured plots, all suf- 

 fered severely. In most cases the difference approaches, and in two 

 cases (Plots 6 and 7 mixed mineral manure, together with 200 and 400 

 pounds of ammonium-salts, respectively furnishing 43 and 86 pounds of 

 nitrogen) it actually exceeds the average produce of the plots. From 

 these facts we see how easy it is to form wrong conclusions as to the 

 effects of different manures, if experiments are conducted in only one 

 season or in only a few seasons, and if the characters of the seasons are 

 not studied. 



Not only season, but soil and locality must exercise an influence. The 

 Rothamsted results are obtained on one description of soil, and in one 

 locality only. Reference to the following table (IX.) shows the results 

 obtained in experiments conducted at Rothamsted during the same 

 eight years, but in two fields; at the same place in one field for thirty- 

 two years; at Woburn, for seven years; at Holkham, Norfolk, for three 

 years; and at Rodmersham, Kent, for four years. Thus, the experi- 

 ments were made on very various soils, under various conditions from 

 previous treatment, and in various seasons, yet the general characters of 

 the results are accordant. 



TABLE IX. 



Results of Experiments on the growth of Wheat by different Manures, 

 on different Soils, in different Localities, and in different Seasons. 



DKESSED GRAIN PER ACRE BUSHELS. 



AVERAGE ANNUAL RESULTS. 



(1) By Ammonium-Salts = only 43 Ibs. N. 



