12 SOIL CONDITIONS AND PLANT GROWTH 



did had it not been for Davy's high reputation. His insistence 

 on the importance of the physical properties of soils — their 

 relationship to heat and to water — was more fortunate and 

 marks the beginning of soil physics, afterwards developed con- 

 siderably by Schiibler (254). On the Continent, to an even 

 greater extent than in England, it was held that plants drew 

 their carbon from the soil and lived on humus, a view sup- 

 ported by the very high authority of Berzelius.^ 



(J)) The Foundation of Agricultural Science. — Hitherto ex- 

 periments had been conducted either in the laboratory or in 

 small pots: about 1834, however, Boussingault, who was 

 already known as an adventurous traveller in South America, 

 began a series of field experiments on his farm at Bechelbronn 

 in Alsace. These were the first of their kind : to Boussin- 

 gault, therefore, belongs the honour of having introduced the 

 method by which the new agricultural science was to be de- 

 veloped. He reintroduced the quantitative methods of de 

 Saussure, weighed and analysed the manures used and the 

 crops obtained, and at the end of the rotation drew up a bal- 

 ance sheet, showing how far the manure had satisfied the needs 

 of the crop and how far other sources of supply — air, rain, and 

 soil — had been drawn upon. The results of one experiment 

 are given in Table I, on the opposite page. At the end of the 

 period the soil had returned to its original state of productive- 

 ness, hence the dry matter, carbon, hydrogen, and oxygen not 

 accounted for by the manure must have been supplied by the 

 air and rain, and not by the soil. On the other hand, the 

 manure afforded more mineral matter than the crop took off, 

 the balance remaining in the soil. Other things being equal, 

 he argued that the best rotation is one which yields the great- 

 est amount of organic matter over and above what is present 

 in the manure. No fewer than five rotations were studied, 

 but it- will suffice to set out only the nitrogen statistics (Table 

 II. on the opposite page), which show a marked gain of nitrogen 



^ J. J. Berzelius, Lehrbuch d. chemic, ubersetz, v. F. Wohler, 3 Aufl., 1839, 

 Bd. 8. 



