52 
INVESTIGATIONS ON ROTH AMSTED SOILS. 
residues. In the surface soil the ratios of carbon to nitrogen vary 
only from 9: 1 to 10: 1; but if two plats be excluded (2b and 13) the 
ratio varies only from 9:1 to 9.8:1, the average being 9.4:1. The 
actual percentage of carbon varies from 0.888 on plat 3 (unmanured) 
to 2.230 on plat 2b (permanently dunged). Excluding the dunged 
plats, it averages 1.076 per cent, or 27,800 pounds of carbon per acre. 
In the second depth the variations in carbon on all the plats lie 
between 0.530 per cent and 0.748 per cent, the latter representing the 
dunged plat. Excluding this, the range is from 0.530 to 0.727, and 
the average is 0.640 per cent, or 17,093 pounds per acre. The ratio 
of carbon to nitrogen ranges from 7.6:1 to 9.7:1, but if two plats 
(viz, the dunged and rape-cake plats) be excluded, the range is from 
7.6:1 to 8.7:1, averaging 8.2:1. 
In the third depth the percentage of carbon shows a range of from 
0.426 to 0.587 (or from 0.426 to 0.535 if we exclude the rape-cake 
plat), and averages 0.492 per cent, or 13,735 pounds per acre. The 
ratio of carbon to nitrogen ranges from 6.7: 1 to 8.2: J (or to 7.8:1 if 
we exclude the rape-cake plat), the average ratio being 7.4: 1. 
In the fourth 9 inches we find a range of carbon from 0.263 per cent 
to 0.414 per cent, with an average of 0.339 per cent, or 9,445 pounds 
per acre. The ratio of carbon to nitrogen varies from 5.6:1 to 7.8: 1, 
and averages 6.6: 1. 
In the fifth 9 inches the carbon drops still lower, ranging from 
0.229 per cent to 0.332 per cent, and averages only 0.279 per cent, or 
8,106 pounds per acre. The ratio of carbon to nitrogen varies from 
5.0:1 to 7.1:1, and averages 5.9:1. 
In the sixth, seventh, and eighth depths the individual variations 
are smaller, save from irregularities of sand, etc., such as have been 
mentioned. The percentages of carbon fall but very gradually, aver- 
aging 0.256, 0.248, and 0.215 (from 7,255 to 6,165 pounds per acre). 
The average carbon to nitrogen ratios are 5.9:1 in both the sixtli and 
seventh depths, and 5.4:1 in t he eighth. 
In the ninth and tenth depths (4 plats only), the quantities of car- 
bon average only 0. L89 per cent and 0.188 per cent, or 5,669 and 5,636 
pounds pei- acre; but one plat shows in these two depths as much as 
0.225 per cent and 0.258 per cent (or 6,75S and 7,745 pounds, respec- 
tively, per acre). 
The table (Table 27) already given shows all the averages at one 
glance, and shows well the diminution of the ratio of carbon to nitro- 
gen and the converse increase in the ratio of nitrogen to carbon. 
The depth at which the carbon ceases to show any marked diminu- 
tion coincides with the depth at which the nitrogen ceases to diminish 
much, viz, a1 the fifth to sixth depth. There also the ratio of carbon 
to nitrogen, which has been rapidly dwindling from the surf ace down- 
ward, suddenly ceases to diminish. It seems that, we at this point 
come to the depth at w hich the nitrogen and carbon are little influ- 
