134 



DR. IT. H. J. MILLER ON THE AMOUNTS OF [May 1903, 



be far greater ; but, as time goes on, the organic matter, which in 

 recently duDged soil contains a relatively high percentage of carbon, 

 will gradually become more and more nitrogenous. Evidence on 

 this point is furnished by some of the results obtained in 1 882, from 

 the soil of the barley-field at Rothamsted. The plots include among 

 others one (7 2 ) permanently dunged, one (7 1 ) which had 14 tons of 

 farmyard manure for the twenty years ending in 1871, but none 

 since, and an unmanured plot (0 1). The percentage amounts of 

 organic carbon and of total nitrogen in the soil dried at 100° are 

 stated in the following table : — 



Table II. — Carbon and Nitrogen in Hoosfield Barley-Soil. 

 (First 9 inches.) 



1 1 



Plot. \ 



Organic 

 Carbon. 



Total 

 Nitrogen. 



Carbon 



tolof 



Nitrogen. 



Nitrogen 



to 100 of 



Carbon. 





14 tons of farmyard manure. . . 



* 



14 tons of farmyard manure. 1 



Unmanured since 1871. J 



Unmanured since 1851 



Per cent. 

 2-486 

 2-032 

 1-021 



Per cent. 

 02131 

 0-1798 

 00930 



11-7 

 11-3 

 110 



8-6 

 8-9 

 9-1 



It is evident that, while the soil of plot 7 1 has lost a certain 

 amount of nitrogen since the application of farmyard manure was 

 discontinued, the loss of carbon has been still greater ; and it is to 

 be expected that some years hence the relations of nitrogen and 

 carbon in this plot will be quite similar to those of the plot O 1, 

 which has been without organic manure since the commencement 

 of the experiments. In a lighter and warmer soil, the reversion to 

 its original state would be more rapid. At Grignon, for instance, 

 Deherain l found that the percentage of carbon in a soil left un- 

 manured was reduced to about half in ten years, but this result 

 must be regarded as quite exceptional. When an application of 

 dung is discontinued, the rate of decomposition will naturally become 

 slower ; and if it happens that non-nitrogenous substances of a 

 relatively stable character are present, the loss of nitrogen may 

 eventually exceed the loss of carbon. 



As regards the effects of extreme conditions of climate, Hilgard 2 

 has investigated the soluble humus in the soils of dry and wet 

 regions in California. He found that, while the total amount 



1 Ann. Agronom. vol. xv (1889) p. 481. 



2 Ann. Eep. Agric. Exper. Stat. Univ. Californ. 1894. p. 6fi. 



