THEORIES CONCERNING SOIL FERTILITY 315 



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 material from the subsoils, 

 far below where the roots go." 



Subsequent to this statement, the following dialogue is recorded : 



The Chairman. "When you say that all soils contain all the elements of 

 plant food, and there is in those soils at all times a saturated solution of which 

 all these elements of plant food make a part, do you not practically say that all 

 soils have all the plant food they need, and that it is at all times available for the 

 plant ; or is it not available for the plant if it is in a saturated solution ? " 



Mr. Cameron. "Certainly, if there is water enough; if the soil is moist." 



The Chairman. "Is it not therefore a justifiable inference from what you 

 have said, that there is all the time in all soils enough plant food available for 

 plant life?" 



Mr. Cameron. "True; perfectly true as regards mineral nutrients." 



The Chairman. "Then I come back again to the question, why is it neces- 

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

 ing material into any soil for the purpose of increasing the amount of plant food 

 in that soil." 



Mr. Cameron. "Not in my judgment." 



The Chairman. "Then in your judgment the only reason for the introduc- 

 tion of fertilizers is for the antitoxic effect or the mechanical effect they may have 

 on the soil." 



Mr. Cameron. "Mainly that, but there are other functions of fertilizers that 

 we know comparatively little about. We know that certain kinds of life, 

 bacteria, molds, can grow in certain solutions of salts, and cannot in others. 

 It may be that fertilizers affect them. But all that is an unexplored field, and 

 little is known about it. ... If you will allow me to say one more word about 

 fertilizers: What are fertilizers? What are the characteristics that a substance 

 must have in order to be a fertilizer? It must be obtained in large quantities. 

 It must also be cheap. Now, the substances which are used as fertilizing mate- 

 rial are substances which can be obtained in large quantities. They are sub- 

 stances, and are the only substances, which we can get hold of that we can 

 get in large quantities, that we can get cheap, and with one exception that is, 

 sodium chlorid common salt. It has not been much used as a fertilizer, 

 because it has not any so-called plant food in it ; and yet it has been used in quite 

 a large number of experiments on quite a large scale, and wherever it has been 

 used, it has generally been found to be quite a good fertilizer. In the investiga- 

 tions of the Bureau we have used pyrogallol. It contains no plant food, but 

 carbon, hydrogen, and oxygen, yet, nevertheless, it is a powerful fertilizer ; ' but 



1 Director Wheeler of the Rhode Island Agricultural Experiment Station reported 

 to the Graduate School of Agriculture held at Cornell University, July, 1908, that 

 a thorough investigation under field conditions at the Rhode Island Station 

 showed practically no benefit from the use of pyrogallol as a fertilizer; whereas, 

 very marked effects were produced by manures and commerical fertilizers. C.G.H. 



