4 F. A. CARLSON 
Pot experiments by Clausen (1906) conducted with clover 
and oats on sandy soil indicated that applications of lime re- 
sulted in a marked nitrogen hunger, especially during dry, hot 
weather and with non-leguminous crops. 
Van Suchtelen (1910) found in laboratory experiments that 
soils treated with calcium oxide produced less carbon dioxide 
than did unlimed soils. 
Alway and Trumbull (1910) say: 
In a comparison of 22 rotation plots. no distinct relation has been found 
between the composition of the soil and the nature of the rotation. In a 
long cultivated field the till was found poorer in humus, nitrogen and organic 
carbon than the lacustral clay. The amounts of the above three constituents 
found in any of the plots depend more upon the relative proportions of the 
two types of soil occurring on the plots than upon the previous treatment. 
The longer the fields have been kept in grasses mown for hay, the less 
has been the change in composition of the soil. Continuous bare cultivation 
along tree rows has caused greater losses than the alternation of fallow 
and crop in the adjacent fields. The extreme loss of nitrogen, humus and 
organic carbon in 25 years is about one-third of the amounts originally 
present in the prairie. 
Bradley (1912) conducted pot experiments from which he 
pointed out that the nitrogen loss was appreciably reduced by 
legumes. 
Mooers, Hampton, and Hunter (1912) reported that the loss 
of nitrogen was appreciably greater on limed plats than on 
unlimed plats, and that the effect extended below the depth of 
plowing. These investigators stated also that there was an 
increase in percentage of humus on the unlimed sections. 
McIntire (1918) writes: 
Burnt lime decreased the organic matter when applied alone and lessened 
the accumulation when applied with manure. 
Calcium sulphate and ground limestone increased organic matter. 
Each form of lime resulted in an increase of nitrogen content, gypsum, 
limestone, and burnt lime, being effective in the order named. 
Lipman and Blair (1913) reported that in their experiments 
the limed plats had lost nitrogen to a greater extent than had 
the unlimed plats. 
Gardner (1914) says: ““Burnt lime appears to exhaust the 
humus in the soil more rapidly than ground limestone. Burnt 
lime with manure gave returns over manure alone. . . . It 
is desirable that the use of lime or limestone lead to larger 
supplies of organic matter in the soil.” 
Swanson (1915) reported results based on the chemical anal- 
yses of cultivated and uncultivated soils in seven representa- 
tive counties in Kansas. He pointed out that the elements 
