5 F. ‘A. CARLSON 
. more nitrogen than the soils in native sod, and 30 per cent more than the 
soils continuously cropped. .... 
In the humid section, the cropped soils have lost 36 per cent oi the 
organic carbon present in the virgin sod and those in alfalfa over 21 per cent. 
Lipman and Blair (1920a) summarized a series of experi- 
ments as follows: 
Lime in the carbonate form was used cn a loam soil at the rate of 1 
ton per acre for the first 5 years and 2 tons for the second 5 years in a 
5-year rotation of corn, oats. wheat and 2 years of timothy. No legume crops 
were introduced. Twenty plots with different nitrogen treatment were thus 
limed and twenty similar plots with parallel nitrogen treatment were left 
without lime. : 
The total yields of dry matter and of nitrogen for the 10-year period 
were essentially the same for the two sections. 
Analyses of the soil made soon after the work was started and again 
at the end of each 5-year period showed that there was a loss of nitrogen 
from both the limed and unlimed sections. However, the loss from the 
limed section was distinctly greater than from the unlimed section. 
Thus at the end of the 10-year period, there was a positive loss rather 
than gain from ‘the use of lime. 
From this work it would appear that the practice of using lime on 
light to medium heavy soils, when leguminous crops are not grown in the 
rotation, may be questionable. Under such conditions it is quite possible 
that a slightly acid reaction may be desirable to prevent the too rapid 
oxidation of organic matter. 
The second five-years period showed a distinct loss in carbon 
from both series. but a greater loss from the limed than from 
the unlimed plats. 
Lipman and Blair (1920b) reported also a series of experi- 
ments which included rotations with legumes. They pointed 
out that during the ten years. the limed plots, with only slight 
exceptions, yielded distinctly larger crops and more total nitro- 
gen than did the unlimed plots. In analyzing the soil they found 
that in a number of cases the limed plots contained more 
nitrogen than did the unlimed plots. 
The same investigators (Lipman and Blair, 1921) reported 
the results of experiments in studying the losses of nitrogen 
and organic carbon from a loam soil (in cylinders with natural 
drainage) which for twenty years had been under a five-years 
rotation of corn, oats (two years), wheat, and timothy. They 
found that in most cases there was a general decline in the nitro- 
gen and the organic carbon content. They pointed out that there 
was a lower nitrogen and organic carbon content in the limed 
soils than in the unlimed soils. They stated also that the legume 
‘green-manure crops tended to raise the nitrogen content. 
It is quite impossible to make any direct comparison of 
