Lecture 5 — 105 — Artificial Media 



field for exploration of the effects of nutrient elements 

 on the metabolism of the plant. 



In a recent period artificial culture methods (water- 

 culture, "hydroponics", sand-culture, gravel-culture) 

 have attracted an extraordinary amount of atten- 

 tion as a means not merely to study general scien- 

 tific principles of plant nutrition, but also to produce 

 crops commercially. Some members of the general 

 public seemed to gain the impression that a revolu- 

 tionary development had taken place and that soon 

 we could dispense with soil as medium for crop 

 growth on a large scale. Many persons also thought, 

 to judge from their letters of inquiry, that plants 

 would grow without light, or in very feeble light, if 

 only the right formula for a nutrient solution were 

 available. But I shall not detain you with the his- 

 tory of this popular exploitation of the water-culture 

 method. I need say only that, save in unusual situa- 

 tions, artificial culture methods including water, sand, 

 and gravel cultures, are at present applicable in a 

 commercial way only to expensive greenhouse crops. 

 Even then practical and economic factors should re- 

 ceive critical consideration before the adoption of a 

 novel technique can be justified. 



The fact that plants that normally grow in soil 

 can be grown in a purely inorganic medium has a 

 rather far reaching significance scientifically, more 

 now than formerly, since so many species have been 

 shown to be adaptable to a water-culture medium. 

 Numerous kinds of plants have been grown in this 

 way through a reproductive cycle. We can, therefore, 

 conclude that no unknown factor is present in the soil 

 which is fundamentally indispensable for the growth 

 of plants, at least of those represented by many agri- 

 cultural species and some others. Evidently the or- 

 ganic matter of the soil so often stressed in considera- 

 tions of soil fertility, is not directly essential from 

 the point of view of the nutrition of the crop plant 



