578 



SCIENCE 



[N. S. Vol. XXXVI. No. 931 



for one plant, the same which at first flourished 

 there? What is the reason one kind of plant suc- 

 ceeds in a field where another fails? 



Liebig answered these questions by say- 

 ing: 



Wheat, clover, turnips, for example, each require 

 certain elements from the soil; they will not 

 flourish where the appropriate elements are absent. 

 Science teaches us what elements are essential to 

 every species of plant by an analysis of their 

 ashes. If, therefore, a soil is found wanting in 

 any of these elements, we discover at once the 

 cause of its barrenness and its removal may now 

 be readily accomplished. 



But has science removed the causes of 

 the barrenness of a soil by the analysis of 

 the soil or of the ashes of the plants? In 

 this connection it might be well to quote 

 a statement from an article by Coleman, 

 which was awarded the prize of the Eoyal 

 Agricultural Society of England in 1855. 

 The author says : 



The causes which operate in producing the fer- 

 tility or barrenness of soils have hitherto to a 

 great extent been shrouded in mystery, not from 

 any want of study, but owing to the difficulties 

 which meet the inquirer at every step and the fact 

 that most important results frequently depend 

 upon causes which have eluded the search of the 

 experimenter. The science of chemistry it was 

 hoped would afEord the key wherewith to unlock 

 the mysteries of nature, but though its discoveries 

 have conferred much practical benefit on the agi'i- 

 culturist, it has up to a very recent period effected 

 comparatively little toward settling the cause of 

 fertility or sterility. The theories of scientific 

 men led us to expect that fertility depended upon 

 the presence of certain mineral substances which 

 were found invariably present in the ashes of 

 plants, and the analysis of the soil it was believed 

 would confirm the practical experience of the 

 farmer; these hopes have been falsified except in 

 the few cases of almost simple soils, such as pure 

 clays and sands. In all other cases the analysis 

 presented the existence in varying proportions of 

 those substances supposed to induce fertility in 

 the barren as well as in the fertile soil. The pro- 

 portion of the various ingredients was next pro- 

 posed as a sign of quality, but researches into the 

 amount of inorganic matter abstracted by each 

 crop have demonstrated that soils of a mixed char- 



acter contain abundant supplies of mineral food 

 for numerous crops. 



This was over fifty years ago, and the 

 statements made are practically as true 

 to-day as they were then. There has been 

 a marked advance in agricultural practise, 

 but until quite recently comparatively 

 little light has been shed upon the scien- 

 tific principles which underlie these prac- 

 tises. 



In all justness to Liebig, however, rather 

 than to his followers, I must make another 

 quotation from his works to show that he 

 himself recognized the insufficiency of the 

 views expressed by the above quotations. 

 He says : 



But it has been observed that the crops are not 

 always abundant in proportion to the quantity of 

 manure employed, even though it may have been 

 of the most powerful kind; that the produce of 

 many plants, for example, diminishes in spite of 

 the apparent replacement by manures of the sub- 

 stances removed from the soil, when they are cul- 

 tivated on the same field for several years in 

 succession. 



From the above quotation it may be seen 

 that Liebig recognized that there are many 

 cases which his theory of mineral require- 

 ment failed to cover. Indeed, if he had 

 followed the idea embodied in the quota- 

 tion to its logical analysis he would have 

 reached some conclusions similar to those 

 presented to you in the various papers 

 to-day. 



Even before, and espeeiallj^ since, the 

 time of Liebig, much material of the kind 

 presented to you by the preceding speaker 

 has been accumulated and handled in the 

 same statistical manner. I should here 

 say that much valuable information has 

 been thus obtained, but it should be need- 

 less for me to add that even with aU these 

 years of crop statistics at hand the difficult 

 problems of the cause of fertility or infer- 

 tility of our agricultural lands have not 

 been thereby determined nor eliminated, as 



