362 INVESTIGATION BY CULTURE EXPERIMENTS 



legume system, and $26.15 in the fallow system, at the prices used 

 in Table 59. (See also comparative statement of prices on page 359.) 



17.84 



TURNIP CROP OF 1908 ON AGDELL FIELD, ROTHAMSTED; 6isi CROP IN 4-YEAR 

 ROTATION; TONS PER ACRE 



5 



Unfertilized 



Mineral plant food 



Minerals and nitrogen 



Counting from the left, lots i, 3, and 5 were grown on land where the rotation is 

 turnips, barley, clover, and wheat, while lots 2, 4, and 6 were grown on land where the 

 rotation is turnips, barley, fallow, and wheat. The six lots were all produced on plots of 

 ground of equal size. Plots i and 2 have received no fertilizer. Plots 3 and 4 received 

 only a phosphorus fertilizer for the 36 years, 1848 to 1883, but since that time they 

 have received mixed minerals, including phosphorus, potassium, magnesium, and sodium. 

 (The average yield of turnips in 1880 was 1% tons for plots i and 2, and the average 

 yield of plots 3 and 4 for the same year was 12% tons per acre.) Plots 5 and 6 have re- 

 ceived mixed minerals and nitrogen since 1848. 



These are the rotation experiments referred to by Professor 

 Whitney on page 22 of U. S. Farmers' Bulletin 257, as follows: 



"In other experiments of Lawes and Gilbert they have maintained for fifty 

 years a yield of about 30 bushels of wheat continuously on the same soil where 

 a complete fertilizer has been used. They have seen their yield go down where 

 wheat followed wheat without fertilizers for fifty years in succession from 30 

 bushels to 12 bushels, which is what they are now getting annually from their 

 unfertilized wheat plot. With a rotation of crops without fertilizers they have 

 also maintained their yield for fifty years at 30 bushels, so that the effect of rota- 

 tion has in such case been identical with that of fertilization." 



In commenting upon these statements, Director A. D. Hall, of 

 the Rothamsted Experiment Station, says: 



"I cannot agree with Professor Whitney's reading of the results on the 

 Agdell field in the least. The figures he quotes for wheat are hardly justifiable 

 as approximations, and are in spirit contrary to the general tenor of the par- 

 ticular experiment. In my opinion the results on the Adgell rotation field are 

 directly contrary to Professor Whitney's idea that rotation can do the work of 

 fertilizers." (See Report of the Committee of Seven, including Woll of Wiscon- 

 sin, Van Slyke of New York, Lipman of New Jersey, Davidson of Virginia, 



