CHAPTER I 



THE SOURCES OF THE NITROGEN OF VEGETATION 



To arrive at a proper understanding of the scheme of the 

 Kothamsted Experiments it is necessary to reconstruct a 

 little the state of the knowledge of agricultural science at the 

 time they were begun in 1843. In many respects it was a 

 period of considerable activity in matters agricultural ; the whole 

 landed interest were making great efforts towards the improve- 

 ment of land and stock and of methods of cultivation ; great 

 areas of the country were being tile-drained and rendered for 

 the first time suitable for arable cultivation, other poor sandy 

 land was being reclaimed by marling and claying. A sign of 

 the times was the establishment of the Eoyal Agricultm'al 

 Society in 1838, and in its earlier volumes, particularly in the 

 writings of Dr Daubeny on the scientific side, and those of 

 Philip Pusey on the practical side, a good idea may be 

 formed of the point of view of the intelligent farmer of that 

 date. The science of the time had just reached a point which 

 enabled a general theory of the nutrition of both plant and 

 animal to be formed. In the latter part of the eighteenth 

 century the researches of Priestley, followed up l)y Ingenhousz 

 and Senebier, had settled the fundamental fact that green 

 plants in sunlight decompose the carbonic acid of the atmos- 

 phere, setting free the oxygen and retaining the carbon, this 

 being the source of the carbon which makes up the bulk uf the 

 dry matter of plants. A little later De Saussure, who pul)lished 



