198 



THE ROTHAMSTED EXPERIMENTS. 



Liebig's 

 view. 



Boussin- 

 gault's in- 

 vestiga- 

 tions. 



Professor 



Daubeny's 



researches. 



Theory of 

 poisonous 

 excretions 

 disproved. 



Rotation 

 and or- 

 ganic and 

 inorganic 

 constitu- 

 ents. 



At first Liebig pronounced this theory of rotation to be the 

 only one having any really scientific basis. Later he seems 

 to have modified his view considerably, and to have supposed 

 that the explanation was — not that the excreted matters of 

 one description of plant were injurious to another of the same 

 description, but that, as the different plants had such very 

 different mineral requirements, the alternation of one kind 

 with another relieved the soil from exhaustion. In his latest 

 work, however, after many years of controversy, he obviously 

 more fully recognised that nitrogen probably played some 

 important part in the matter. 



More than fifty years ago Boussingault published the 

 results of an investigation, extending over a period of ten 

 years, to determine the chemical statistics of some of the 

 rotations actually followed in his own locality, in Alsace; 

 and he came to the conclusion that the difference in the 

 amounts of nitrogen taken up by the different crops constituted 

 a very important element in the explanation of the benefits 

 of rotation. 



We can only further briefly refer to the results and con- 

 clusions of the late Professor Daubeny, of Oxford, who com- 

 menced a series of experiments in the Botanic Garden there 

 in 1834. One of the original objects he had in view was to 

 test the truth of De Candolle's theory that the excretions of 

 one description of plant were injurious to plants of the same 

 description. He soon came to a negative conclusion on the 

 subject; and recognised the validity of Boussingault's argu- 

 ment, that the actual facts of vegetation in different parts of 

 the world conclusively showed that the same description of 

 plant may continue to grow healthily on the same land for 

 long periods of time. On this point it is scarcely necessary 

 to add that the experience at Eothamsted on the growth of 

 various agricultural crops year after year on the same land 

 for many years in succession is conclusive against the theory 

 of injurious or poisonous excretions. 



But, as already said, Dr Daubeny continued his experi- 

 ments for ten years ; and although, in accordance with the 

 prevailing ideas of the time, all his analytical results related 

 to the mineral constituents of his soils and crops, his main 

 conclusion was, that the benefits of rotation were probably 

 as much connected with the available supply of the organic 

 as of the inorganic constituents. 



What, then, are the indications of the results of many years 

 of investigation of the subject, in the field and in the labora- 

 tory, at Eothamsted ? 



