14 SOIL CONDITIONS AND PLANT GROWTH 



when the newer rotations are adopted, but not where wheat 

 only is grown. 



Now the rotation has not impoverished the soil, hence he 

 concludes that " I'azote peut entrer directement dans I'organ- 

 isme des plantes, si leur parties vertes sont aptes ^ le fixer ". 

 Boussingault's work covers the \^hole range of agriculture and 

 deals with the composition of crops at different stages of their 

 growth, with soils, and with problems in animal nutrition 

 Unfortunately the classic farm of Bechelbronn did not remain 

 a centre of agricultural research and the experiments came to 

 an end. Some of the work was summarised by Dumas in a 

 very striking essay (88, see also 47) that has been curiously 

 overlooked by agricultural chemists. 



During this period (1830 to 1840) Carl Sprengel was 

 studying the ash constituents of plants, which he considered 

 were probably essential to nutrition (270). Schiibler was 

 working at soil physics (254), and a good deal of other work 

 was quietly being done. No particularly important discoveries 

 were being made, no controversies were going on, and no 

 great amount of interest was taken in the subject. 



But all this was changed in 1840 when Liebig's famous 

 report to the British Association upon the state of organic 

 chemistry, afterwards published as Chemistry in its Application 

 to Agriculture and Physiology (174^), came like a thunderbolt 

 upon the world of science. With polished invective and a fine 

 sarcasm he holds up to scorn the plant physiologists of his day 

 for their continued adhesion, in spite of accumulated evidence, 

 to the view that plants derive their carbon from the soil and 

 not from the carbonic acid of the air. " All explanation"^ of 

 chemists must remain without fruit, and useless, because, even 

 to the great leaders in physiology, carbonic acid, ammonia, 

 acids, and bases, are sounds without meaning, words without 

 sense, terms of an unknown language, which awake no thoughts 

 and no associations." The experiments quoted by the physi- 

 ologists in support of their view are all "valueless for the de- 

 cision of any question ". " These experiments are considered 

 by them as convincing proofs, whilst they are fitted only to 



