3 i8 SYSTEMS OF PERMANENT AGRICULTURE 



5. "I have attempted to show you the way I believe fertilizers act and the 

 reason we use them. I think that this is the way stable manure and green 

 manures act. I think that is the principal office of nitrate of soda, potash, and 

 phosphoric acid ; but they do not all act alike on the same soils. We are work- 

 ing now on a soil in Iowa which with stable manure every time produces a 

 smaller crop than without. . . . 



6. "There is another way in which the fertility of the soil can be maintained, 

 viz., by arranging a system of rotation and growing each year a crop that is not 

 injured by the excreta of the preceding crop; then when the time comes round 

 for the first crop to be planted again, the soil has had ample time to dispose of 

 the sewage resulting from the growth of the plant two or three years before." 



WHITNEY, in Farmers' Bulletin 257, page 21. 



7. "The soil solution is bringing materials from below which the plant gets, 

 and as a matter of fact the most important discovery of the Bureau of Soils in 

 recent years is that plants are feeding on materials from the subsoils, far below 

 where the roots go." 



CAMERON, in the Hearings before the Committee on Agriculture of the 



United States House of Representatives, page 446 (1908). 



8. The Chairman. "Then I come back again to the question, Why is it 

 necessary, or is it in your judgment necessary, ever at any time to introduce 

 fertilizing material into any soil for the purpose of increasing the amount of 

 plant food in that soil?" 



Mr. Cameron. " Not in my judgment." 



Hearings before the Committee on Agriculture of the United States House 



of Representatives, page 446 (1908). 



9. " In the truck soils of the Atlantic coast, where 10 or 15 tons of stable 

 manure are annually applied to the acre, in the tobacco lands of Florida, and of 

 the Connecticut Valley, where 2000 or 3000 pounds of high-grade fertilizers 

 carrying 10 per cent of potash are used, even when these applications have been 

 continued year after year for a considerable period of time, the dissolved salt 

 content of the soil as shown by this method is not essentially different from that 

 in surrounding fields that have been under extensive cultivation. 



"In England and in Scotland it is customary to make an allowance to tenants 

 giving up their farms for the unused fertilizers applied in the previous seasons. 

 The basis of this is usually taken from 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." 



- WHITNEY and CAMERON, in Bureau of Soils Bulletin 22, page 59. 



The question may be asked if the plant food brought to the sur- 

 face by capillary moisture in humid sections is greater than that 

 lost by leaching. Compare, for example, the composition of the 

 old prairie soil (gray silt loam) in the lower Illinoisan glaciation 



