100 
it seems to classify a soil more accurately than any other single factor in- 
vestigated. It will be noted from all tables that the nitrogen, phosphorus, 
acid soluble matter and crop yield increase as the per cent of organic 
matter increases. 
The plant food soluble in dilute acid (1/5) is 1.98 per cent for soils in 
table 1 having a volatile content of 2 to 3% whereas that for table 7 con- 
taining 10% or over averages 7.83% soluble in this acid, besides the latter 
shows a high corn yield compared with that shown in tables 1 and 2. 
It will be noted that nearly all soils produced some carbon dioxide gas 
(4 to 6 ce. e.) when treated with hydrochloric acid including those slightly 
acid to litmus. This indicates that a small evolution of gas when treated 
with acid does not prove the soil is not acid as is often noted in the liter- 
ature. 
It will be noted also from tables 1, 2 and 3 containing low organic matter 
that the soils most acid to litmus belong in these three groups and embrace 
about 70 per cent of the total. In comparing the nitrogen content of the 
different groups of soils noted in tables 1 to 7 with that of counties previ- 
ously reported in the Proceedings it is found that the clay soils with a 
volatile content of 0 to 4% contain the following amounts of nitrogen in 
Ibs. per acre for the different counties. Elkhart County 2,049, Allen County 
3,667, Hancock County 2,779, and Cass County 1,745. 
Where the clay loams predominate with a volatile content of 4 to 6% 
Elkhart County contained 2,553 Ibs. of nitrogen per acre, Allen County 3,985 
lbs., Hancock County 3,572 and Cass County 2,700. 
The loam soils with a volatile content varying from 6 to 10% were higher 
still—Elkhart County soils contained 4,213 Ibs. per acre, Allen County 5,305, 
Hancock 5.259, and Cass County 4,411. The above figures were obtained 
from the analyses of over 400 samples of soils representing all townships 
in each of the counties. 
