November 8, 1912] 



SCIENCE 



621 



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 fol- 

 lowed wheat without fertilizer 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 rotation has in such case been identical 

 with that of fertilization. (Pages 21, 22.) 



If we turn to the Rothamsted data, we 

 find that the first recorded yield of wheat 

 on the unfertilized plot on Broadbalk Field 

 was not 30 bushels, but only 15 bushels; 

 that the average of the first eight years 

 was 17.4 bushels; that the best fertilized 

 plot on the same field has averaged not 30 

 bushels, but 37.1 bushels for fifty-five 

 years; that, as stated above, the wheat 

 grown in rotation, following a leguminous 

 crop, has averaged not 30 bushels, but 25 

 bushels on unfertilized land, and 34.8 

 bushels where fertilizers are applied for 

 turnips three years before. 



The following pertinent quotations are 

 from Whitney and Cameron in Bureau of 

 Soils Bulletin 22 : 



In England and Scotland it is customary to 

 make an allowance to tenants giving up their 

 farms for the unused fertilizers applied in previous 

 seasons. The basis of this is usually taken at 30 

 to 50 per cent, for the first year, and at 10 to 20 

 per cent, for the second year after application; 

 but, in the experience of this bureau there is no 

 such apparent continuous effect of fertilizers on 

 the chemical constitution of the soil. (Page 59.) 



It appears further that practically all soils con- 

 tain sufficient plant food for good crop yield; 

 that this supply will be indefinitely maintained. 

 (Page 64.) 



In Bureau of Soils Bulletin 55, by 

 Whitney, entitled "Soils of the United 

 States," issued in 1909, we find under the 

 heading "Permanency of Soil Fertility as 

 a National Asset" the following summar- 

 ized statements: 



The soil is the one indestructible, immutable 

 asset that the nation possesses. It is the one 

 resource that can not be exhausted; that can not 

 be used up. (Page 66.) 



From the modern conception of the nature and 

 purpose of the soil it is evident that it can not 

 wear out, that so far as the mineral food is con- 

 cerned it will continue automatically to supply 

 adequate quantities of the mineral plant food for 

 crops. (Page 79.) 



As a national asset the soil is safe as a means 

 of feeding mankind for untold ages to come. 

 (Page 80.) 



As stated in the beginning, I have not 

 planned to discuss the subject of plant 

 food in relation to soil fertility; but I felt 

 it a duty as well as an honor to be per- 

 mitted to accept a place on your program; 

 and I have placed before you some most 

 important and trustworthy data bearing 

 upon the question. I have presented some 

 statistics for consideration in connection 

 with the gravest problem which now con- 

 fronts America; namely, the problem of 

 restoring American soil and of maintain- 

 ing American prosperity. I have quoted 

 accurately and fairly from the teachings 

 of Whitney and Cameron; and I also sub- 

 mit for your information the following 

 quotation from Director A. D. Hall, of 

 Rothamsted : 



I can not agree with Professor Whitney's read- 

 ing of the results on the Agdell field in the least. 

 The figures he quotes for wheat are hardly justi- 

 fiable as approximations, and are in spirit con- 

 trary to the general tenor of the particular experi- 

 ment. ... In my opinion the results on the Agdell 

 rotation field are directly contrary to Professor 

 Whitney's idea that rotation can do the work of 

 fertilizers. (From Eeport of the Committee of 

 Seven, appointed by the Association of Official 

 Agricultural Chemists "to consider in detail the 

 questions raised," published in full in Circular 

 123 of the University of Illinois Agricultural 

 Experiment Station.) 



A thousand additional proofs of the 

 practical value and of the evident neces- 

 sity of supplying plant food in systems of 



