ACCUMUJ.ATION Ol' FKiMII,ir\ 



i:;i^ 



carrying other Icgimiiaou.s plants, ur at least has so reduce. 1 

 ley are unable to resist the coiniKiition 



their vigour that tl 



of the grasses in a natural herbage. 



Table LI. — Accumulation of Carbon and NUroncn in >>t)i/ of .\r„},l, 

 Land allowed to run wild for over 20 years. 



* IJroadbalk, 1881 ; Geescroft, 1SS3. 



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 -ll')2 percent, 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 

 the original sample from arable land. For these reasons it is 

 necessary to reduce the estimate made of the annual gain of 

 nitrogen, but however large an allowance be made on this 



