40 
INVESTIGATIONS ON ROTHAMSTED SOILS. 
RAPE-CAKE PLAT. 
Next in order to the dunged plats in point of richness in total 
nitrogen is the only other plat of the series which has been persist- 
ently treated with organic nitrogenous manure, viz, plat 10, which 
constantly receives rape cake, the quantity since 1883 being from 1G 
to 17 hundredweight per annum, estimated to contain 9o pounds of 
nitrogen per annum. The crops yielded by this plat have been 
inferior to those of most of the chemically manured plats receiving 
inorganic nitrogen (ammonium salts or sodium nitrate) with a liberal 
supply of minerals. But there has been accumulated a distinctly 
larger quantity of organic nitrogen; that is to say, there is in the 
surface soil an accumulation of nitrogen clearly due to the organic 
matter of the manure, apart from that due to crop residues. We may 
compare this plat with plat '6 (wholly unmanured), and with the 
average of plats 7, 11, 12, 13, 14, 15, and 16, all receiving annually 
nearly as much nitrogen as the rape-cake plat, but in the form of 
ammonium salts or sodium nitrate, and also receiving phosphates 
with or without various alkaline salts. 
Table 20. — Broadbalk ivheat soils, 1893 — Comparison of chemically manured plats 
and Rape-cake plat. 
NITROGEN. 
Plat. 
Average yield 
for forty-two 
years. 
Per cent. 
Pounds per acre. 
Wheat. 
Straw. 
First 
9 
inches. 
Second 
9 
inches. 
Third 
9 
inches. 
First 
9 
inches. 
Second 
9 
inches. 
Third 
9 
inches. 
Bushels. 
Cwt 
12* 
10f 
0. 0992 
0.0730 
0. 0851 
2,572 
1,950 
1,817 
Average of plats 7, 11, 12, 13, 14, 15, 
and 16. Minerals with ammo- 
nium salts (or sodium nitrate) 
containing 86 pounds nitrogen 
per annum 
291 
29 
.1196 
.0788 
.0662 
3, 100 
2, 106 
1,848 
Plat 19, rape cake, containing 93 
.0719 
pounds nitrogen per annum . . . 
28 
25* 
.1348 
.0794 
3,478 
2,121 
2,007 
CARBON. 
Plat 3, unmanured 
12} 
ioi 
0.888 
0. 565 
0.483 
23,022 
15,093 
13,483 
Average of plats 7,11,12, 13, 14, 15, 
and 16. Minerals with ammo- 
nium salts i or sodium nitrate) 
containing 86 pounds nitrogen 
per annum 
29.} 
29 
1.124 
.641 
. 485 
29, 141 
17,112 
13,685 
Plat 1!), rape cake, containing 93 
pounds nitrogen per annum ... 
28 
25| 
1.257 
.719 
.587 
32,430 
19,307 
16,385 
As more organic matter has been formed above ground, as grain and 
straw, in the average of the plats receiving ammonium salts, we may 
suppose thai more stubble and root residue has on the average been 
left by each crop than on the rape-cake plat. The much Larger nitro- 
gen accumulation, therefore, in the surface soil of the rape-cake plat 
musl be attributed to the direct accumulation of nitrogenous organic 
matter from the rape cake itself. Not only does the surf ace- soil con- 
