24 EF. A. CARLSON 
The most important result shown in figures 1 and 2, as 
related to the present investigation, is the increase in yields of 
crops on the limed plats over those on the unlimed plats. 
SUMMARY 
A study of the effect of various treatments and cropping 
systems on the organic carbon and the nitrogen in soil is re- 
ported in this paper. The soil is classified as a Dunkirk clay 
loam. The plats were each 1/100 of an acre in size and were 
arranged in two series. The treatments included manure, potas- 
sium sulfate. and lime. The cropping consisted of a rotation 
without legumes, a rotation with legumes, and grass perma- 
nently. The experiment was conducted for periods of eight and 
ten years, respectively. 
The plats were sampled for the first- and second-foot strata 
before and after treatment. 
The organic carbon and the nitrogen were determined. 
The results of the two series compared favorably. 
In genera! the limed plats in both series contained more 
organic carbon and nitrogen than did the unlimed plats. 
There was a decrease in organic carbon and in nitrogen at 
the end of the period of experimentation on the plats in rotation 
without legumes. 
The plats kept in grass showed an increase in organic car- 
bon and in nitrogen. 
The plats in rotation with legumes contained more nitro- 
gen than did the plats in rotation without legumes. The plats 
in rotation with legumes in Series II showed a marked increase 
in nitrogen. The increase was greater in the limed plats than 
in the unlimed plats. This fact seems to indicate that the leg- 
umes had some infiuence on the nitrogen content of the soil 
studied. 
The organic carbon and the nitrogen were lower in the 
plats of Series II than in the plats of Series I. 
The limed plats produced higher yields of crops than did 
the unlimed plats. 
The plats in Series I gave higher yields of crops than did 
the plats in Series II. 
The results suggest that there is some relation between or- 
ganic carbon and nitrogen, and yields of crops. 
