38 INVESTIGATIONS ON ROTH A.MSTED SOILS. 
TOTAL NITROGEN IN UNMANURED AND IN CONTINUOUSLY 
DUNG-ED PLATS. 
The two plats which seem naturally to claim our first attention are 
the plats which for fifty years have been the most diverse in their 
treatment, namely, the continuously cropped but wholly unmanured 
plat (No. 3), with its almost unmanured companion (No. 4) on the 
one hand, and on the other hand plat 2b, which in the course of the 
fifty years ended in 1893 had received no less than 700 tons of dung, 
estimated to have supplied 200 pounds per annum, or in all 10,000 
pounds, of nitrogen, the greater part of which would originally exist 
in an organic condition, and we naturally look at once to see how 
their nitrogen contents compare. Glancing down the columns of 
Table 13 we find, as we should expect, that, as regards nitrogen, they 
are respectively the poorest and the richest of the plats. 
We find as follows : 
Table 17 .—Broadbalk wheat soils {1893) , plats 3, 4. and 2b. 
Nitrogen. 
Per cent. 
Pounds 
per acre. 
Plat 3, continuously unmanured (first 9 inches only) 
0. 0992 
2,572 
Plat 4, unmanured since 1852 (first 9 inches only) 
.0982 
2,546 
Plat 2b, 14 tons farmyard manure per annum (first 9 inches only) 
.2207 
5, 151 
Plats 3 and 4, then, have less than 0.1 per cent of organic nitrogen, 
while plat 2b has over 0.22 per cent. 
Allowing for the differences of lightness in the soils (see previous 
discussion), the permanently dunged surface soil contains as nearly 
as possible twice as much organic nitrogen as the unmanured soil, the 
excess in round numbers being about 2,500 pounds per acre. 
The manured plat has yielded in its crops in fifty years something 
like 1,600 pounds more of nitrogen per acre than the unmanured plat. 
Of 1 lie total 10,000 pounds of nitrogen estimated to have been supplied, 
then, we find (in rough, round numbers) that 1,G00 pounds have been 
recovered in the increased crops, and that about 2>500 pounds are 
found in the surface soil, leaving 5,000 (or, in round numbers, 6,000) 
pounds to be accounted for otherwise. 
In the second !) inches we find: 
Table 18.— Broadbalk wheat soils (1S93), plats 3, 4, and ?b (second 9 inches). 
Nitro^fM'. 
Per cent. 
Pounds 
per acre. 
Plat continuously unmanured (second 9 inches) 
f6xp 
© * ' 
1,950 
2,092 
2,049 
Plat 4. unmanured wince 1852 (second 9 inches) 
I'i.it ::),, It tons farmyard manure per annum (second 9 inches). 
