ACCUMULATION OF FERTILITY 



139 



plants (beans and clover) had in some way unfitted the soil for 

 carrying other leguminous plants, or at least had so reduced 

 their vigour that they were unable to resist the competition 

 of the grasses in a natural herbage. At the present time 

 leguminous plants are making their appearance in some 

 quantity, and are tending to spread. 



TABLE LI. Accumulation of Carbon and Nitrogen in Soil of Arable 

 Land allowed to run wild for over 20 years. 



* Broadbalk, 1881 ; Geescroft, 1883. 



Note. In November 1885 (that is, after the land had grown Barley and Clover in 1883, 

 and Clover in 1884 and 1885), samples were taken of the first 9 inches of soil from the 

 same portion of the field as in 1883 (Plots 1-10), and gave a mean of -1152 per cent, of 

 Nitrogen. 



The most noteworthy fact is the enormous accumulation of 

 nitrogen : during the twenty-year period the Broadbalk wilder- 

 ness would appear to have gained nearly 98 lb., and Geescroft 

 a little more than 44 lb. of nitrogen per acre per annum. The 

 gain in carbon is less pronounced, although the amount accumu- 

 lated is greater than that of nitrogen, yet the ratio of carbon 

 to nitrogen in the increase is very much lower than the ratio 

 in ordinary vegetable matter or in the original organic matter 

 of the soil. 



Owing, however, to changes in the consolidation of the 

 ground it is difficult to secure an exact comparison of the 

 same layer of soil at the two periods, i.e., the surface nine 

 inches after the land has been in grass for some time will contain 

 a certain amount of recent turf, and less of the poor subsoil than 



