18 BOARD OF AGRICULTURE. 



ordinary interest ; it is vital ; a proper understanding or a 

 misunderstanding of the principles, making all the difference 

 between success and failure in his life-work. We must admit 

 that the investigation of this subject of plant-nutrition, by 

 scientific men, is one of modern date. In fact, it is true that 

 for more than forty years scientific belief on this subject has 

 been in a sort of transition state. Many of the theories 

 which have been openly advocated have been found, by dis- 

 covery and experiment, to have been without foundation. 

 Scientific men have vacillated for forty years in relation to 

 this matter of the principle of plant-nutrition. 



At one time it was believed and openly advocated that 

 plants depend for their nutrition upon the organic matter, or 

 humus, in the soil. The humus theory had its day ; and yet, 

 when the touch of chemistry was put to it, it was found that 

 certain soils were extremely fertile with only two or three per 

 cent, of humus in their composition, and certain other soils 

 were sterile with twenty, thirty or forty per cent, of humus 

 in their composition. Then the humus theory went to the 

 wall. Afterwards it was advocated, and even by the great 

 Liebig, that, for their nutrition, plants needed only the ap- 

 plication of the mineral elements ; but he was met by the 

 nitrogen theory men, and the contest went on, year after 

 year, between the advocates of nitrogen and the advocates of 

 minerals, until at length it was discovered that in some of 

 their assumptions both the nitrogen men and the mineral men 

 were wrong, and in some of their assumptions both the nitro- 

 gen men and the mineral men were right. 



Then, in due course of time, came the theory, that in order 

 to ascertain the wants of plants, that we might provide them 

 with proper nutrition, it was simply necessary to analyze the 

 soil, determine its wants and the structure or the composi- 

 tion of plants, and then the farmer might apply to his soil 

 the elements in which it was deficient, and the plant would 

 have an abundant supply of nutriment. But it was soon 

 found that the acids of the chemist could wring from a sam- 

 ple of soil in the laboratory certain elements, which were sup- 

 posed to be elements of nutrition, which the plant never 

 could find in the soil ; and that although the acid of the 

 chemist might determine positively that there was an abun- 



