1. Soil nitrogen cannot be used by plants until it is changed
to the form of nitrate nitrogen by the nitrifying bacteria. Page 307
2. Atmospheric nitrogen cannot be used by any agricultural
plants, excepting legumes, and even leguminous plants have no
power to obtain nitrogen from the air unless they are provided
with the proper nitrogen-gathering bacteria. Page 309
3. As a rule each important agricultural legume must have its
own particular species of bacteria. Page 311
4. The frequent failure of red clover in normal seasons,
especially on normal soils occupying the highest land, is
undoubtedly due in part at least to the absence of the proper
bacteria (sometimes the soil lacks lime or phosphorus). Page 313
5. On the very acid soils, where clover has never been grown
successfully, applications of ground limestone should be made
where legumes are to be grown. Page 315
6. Cowpeas need not be inoculated, because the cowpea bacteria
are usually either present in the soil or are introduced with
the seed in sufficient numbers to effect a good degree of
infection if the soil is suitable and if cowpeas are seeded
upon the same land for two successive years. Page 317
7. Cowpeas grown on infected soil on the University of Illinois
soil experiment field contained four times as much nitrogen as
the same kind of cowpeas grown on similar land which was not
infected. Page 319
8. As a rule soy bean fields should be inoculated when first
seeded to soy beans, otherwise they may be grown on the same
land for three or four years before the soil becomes thoroughly
infected. Page 320
9. Investigations, reported in this bulletin, furnish
conclusive proof that infected sweet clover soil can be used
for inoculating alfalfa fields and with the same results as are
obtained when the infected soil is obtained from an old alfalfa
field. (Sweet clover is a tall, rank-growing, sweet-scented
leguminous plant widely distributed over Illinois, especially
along the roadsides in the northern and central parts of
the state, and in many places in bottom lands in southern
Illinois.) Page 324
10. This bulletin will be sent free of charge to any one
interested in Illinois agriculture upon request to E.
Davenport, Director Agricultural Experiment Station, Urbana,
Illinois; and, if so requested, the name of the applicant will
be placed upon the permanent mailing list of the Experiment
Station, so that all bulletins will be sent to him as they are
issued.