48 THE SPIRIT OF THE SOIL 



because of his mistaken view of the way in which 

 plants obtained theft Nitrogen. 



Lawes, the pioneer experimenter on agriculture in 

 England, whose work at Rothamsted had been for 

 some years in progress, flatly denied the accuracy of 

 several of Liebig's conclusions, and as a result of 

 further experiments conducted by himself and 

 Gilbert, made several important discoveries in con- 

 nection with mineral manures. These do not con- 

 cern us here ; what is of importance from our present 

 standpoint is that by 1855 Lawes and Gilbert had 

 established that 



1. The beneficial effect of fallowing lies in the 

 increase brought about in the available nitrogen 

 compounds in the soil. 



2. Non - leguminous plants require a supply of 

 some nitrogenous compounds, nitrates and Am- 

 monium salts being about equally good. The amount 

 of Ammonia obtainable from the atmosphere is in- 

 sufficient for the needs of crops. Leguminous plants 

 behave abnormally. 



The experiments had been conducted on the fol- 

 lowing lines: A long list of plants, leguminous and 

 others, had been grown in surroundings free from 

 Ammonia or any Nitrogen compound. The soil in 

 which they grew had been burnt; the air furnished 

 them was washed and purified, but they were sup- 

 plied with everything necessary in the form of 

 mineral foods. All but the leguminous plants 

 languished and died. The leguminous plants, how- 

 ever, were found to flourish. They assimilated large 

 quantities of Nitrogen into their tissues, and the soil 



