THEORIES CONCERNING SOIL FERTILITY 317 



gather their food from. All soils having, broadly speaking, all of these minerals 

 in them, have approximately the same composition in their soil moisture. 



"This is a very astonishing fact, but, looked upon in the light of our experi- 

 ments, it is an actual fact that all soils contain sufficient plant food for the sup- 

 port of plants. Further, when the plant takes into its substance some of the 

 mineral matter from the solution, the solid minerals in contact with the solution 

 immediately dissolve, and the solution is restored to its former concentration. 

 The exhaustion of the soil, therefore, is merely a relative phrase and resolves 

 itself into the question of the rate at which the solution can recover itself. 

 I may state to you that the rate is as fast on an acre planted in our ordinary crops 

 as the demand made upon it by the plant." 



WHITNEY, in Farmers' Bulletin 257, pages 10, n. 



3. "It is not to be denied that plants will not infrequently do better when 

 they are growing in a soil, a nutrient solution, or a soil solution many times 

 stronger than they actually need. . . . 



"If we take a plant and grow it in a water culture, the plant does better if we 

 have a solution containing several times more phosphorus and potash than it 

 actually needs to feed on. Why it is we do not know, but granting that the plant 

 does better in a solution stronger than it actually needs as a food, we still have 

 a solution in the soil apparently strong enough for any need the plant may have. 



"Now we come to a very interesting thing to the farmer. If soils have suffi- 

 cient food for the needs of plants and if this supply is constantly maintained, as 

 I say, by the solution of these minerals in the soil, then what is the function of 

 fertilizers, and what do we mean by worn-out lands or exhausted lands ? . . . 

 The chemical idea of the exhaustion of a soil is not logical in the light of the ex- 

 perience which all of us have seen, that when fertilizers are applied, the soils are 

 not always made immediately productive. You can go into many of the regions 

 of the worn-out soils of our Eastern states and reclaim those soils or make 

 them productive, but not with any amount of fertilizers you can apply." 



"I should say that the soil ought to take care of the excrement of plants. It 

 is its business to do so. It is its proper function. Whether it does this through 

 the agency of bacteria, whether it is due to the abnormal absorptive power of 

 the soil or to direct oxidation, we do not know. It is probably due in part to 

 each. Take a natural soil, a prairie sod; the sanitary conditions in that soil 

 are almost perfect." * 



WHITNEY, in Farmers' Bulletin 257, pages n, 12, and 15. 



4. "Apparently these small amounts of fertilizers we add to the soil have 

 their effect upon these toxic substances and render the soil sweet and more 

 healthful for growing plants. We believe that it is through this means that our 

 fertilizers act rather than through the supplying of plant food to the plant." 



WHITNEY, in Farmers' Bulletin 257, page 20. 



1 See Table 70 for effect of plant food on permanent grass park more than 250 

 years old. C. G. H. 



