Volume IX OCTOBER, 1919 Part IV 



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THE AMOUNT AND COMPOSITION OF RAIN 

 FALLING AT ROTHAMSTED. 



(BASED ON ANALYSES MADE BY THE LATE NORiUN H. J. MILLER.) 



By E. J. RUSSELL and E. H. RICHARDS. 

 {Rolhamsted Experimental Station.) 



The composition of rainwater was a matter of serious interest to the 

 agricultural chemists of the last generation. It was a side issue of the 

 great controversy on the source of nitrogen for plant life, which occupied 

 much time and energy between 1840 and 1870. The main issue was 

 whether plants could or could not assimilate free nitrogen from the 

 air ; this was settled in the case of non-leguminous crops by the investi- 

 gations of Lawes, Gilbert and Pugh in 186P. The side issue was whether 

 the nitrate and ammonia necessary for vegetation would need to be 

 supplied by fertilisers or whether the natural stores in the rain and the 

 air would suffice. 



Liebig had stated^: 



"If the mineral elements, phosphates, etc., be duly supplied, the 

 plant will obtain a sufficient supply of ammonia from the atmosphere": 



and again: 



"If the soil be suitable, if it contains a sufficient quantity of alkalis, 

 phosphates and sulphates, nothing will be wanting. The plants will 

 derive their ammonia from the atmosphere as they do carbonic acid*." 



Liebig clearly supposed that there was a considerable amoimt of 

 nitrogen in the rain, and while he does not seem to have committed 

 himself to any figure in his earlier writings, he published in 1863* an 

 estimate of 24 lb. of nitrogen per acre per annum. 



Lawes and Gilbert did not accept this position. They showed by 

 field experiments that the crop yield is proportional to the ammonia 



' Phil. Trans., 1861, Part ii, 431. 



^ Letters on Chemistry, 1851, 3rd ed., 519. In this Letter, the 34th. Liebig sets out 

 his views with characteristic clearness. 

 ' Farmers' Magazine, 1847, 16, 511. 

 ♦ Natural Laws of Husbandry, 1863, 290. 



Joom. of Agrio, Sci. ix 21 



