18 F. A. CARLSON 
assume that an increase in yield is associated with an increase 
in roots and residual organic matter, which may explain why the 
organic carbon and the nitrogen were generally higher in the 
limed plats than in the unlimed plats. 
The total yields were less on the plats kept permanently in 
grass than on the plats in rotation with legumes or on those in 
rotation without legumes. It has already been pointed out, in 
tables 2 and 38, that the plats in rotation lost more organic car- 
bon and nitrogen in the first foot than did the grass plats. 
SERIES II 
In order to obtain further information on the effect of 
treatment and cropping on the organic carbon and the nitrogen 
in soils, the plats in Series II, located adjacent to plats in Series 
I, were analyzed. These plats, as already stated, received ap- 
proximately the same treatment as the plats in Series I, the only 
marked differences being that the plats of Series II were started 
one year later than the plats of Series I, and that they received 
only two applications of manure. 
Only the first foot was analyzed, due to the failure of the 
second foot in Series I to show any consistent results of experi- 
mental value. 
The results obtained are recorded in tables 6, 7, and §&. 
These tables are not discussed separately, due to their close 
correlation with the results of Series I. 
The points emphasized in discussing the results of Series 
I may well be applied to Series II. However, the results in 
Series II are much more striking. The limed plats, as was 
found in Series I, show in general a higher percentage of organic 
carbon and of nitrogen than do the unlimed plats. The limed 
plats also gave higher yields than did the unlimed plats. There 
was a decrease in organic carbon and in nitrogen in the plats 
cropped under the rotation without legumes, with one exception. 
The most interesting phase of these results is that the plats 
in rotation with legumes showed an increase in nitrogen. The 
percentages are very significant. Plats 7205 and 7211, in rota- 
tion with legumes, increased 4.2 and 6.7 per cent, respectively, 
in comparison to plats 7202 and 7208, in rotation without leg- 
umes, which decreased in nitrogen 12.2 and 7.1 per cent, re- 
spectively. 
