Soil Changes Produced By Micro-organisms. 
33 
isolated and grew them upon an artificial culture medium com¬ 
posed of a decoction of pea leaves, gelatin, asparagin and sac¬ 
charose. To the causal organism he gave the name Bacillus radi- 
cicola. 
Following close upon the discovery of the relation of nodule 
bacteria to nitrogen fixation in the Leguminosae came the idea of 
utilizing these bacteria commercially. Experiments had shown 
that where soils were deficient in these germs, they could be made 
much more productive if inoculated with a soil known to contain 
an abundance of the coveted organisms. Accordingly, there have 
appeared on the market in recent years pure cultures of these bac¬ 
teria under the trade names of “Nitragin,” “Nitro-Culture,” etc. 
It was intended primarily to use this material on the seed, but it 
could be employed to inoculate the soil if desired. Columns of 
print have been used to exploit these preparations which are offered 
for sale at the modest price of $2.50 for material sufficient for one 
acre. 
The first cultures that were distributed in this country were 
put up in a dry condition on small tufts of absorbent cotton. From 
these, the purchaser prepared his own liquid culture with which to 
inoculate the seed by adding the dried material to a certain nutrient 
solution, the ingredients of which accompanied the cotton. This 
method failed for two reasons: first, the bacteria could not with¬ 
stand the drying on the cotton; and second, the farmer possessed 
neither the facilities nor the technical skill necessary to grow the 
liquid cultures and keep them pure. The outcome was cultures 
of doubtful purity and virulence, with a glaring lack of uniformity 
and agreement in the results obtained by using them. This diffi¬ 
culty has been overcome in a large measure by the preparation and 
sale of concentrated liquid cultures and cultures put up on a solid 
medium, so that all the purchaser is required to do now is to shake 
up or mix the cultures with a stipulated amount of clean water, and 
use this at once to inoculate the seed. Ivellerman, of the U. S. De- 
partment of Agriculture, reports successful inoculations in 76 per 
cent, of his field tests with the liquid culture, and Edwards, of the 
Guelph, Ontario Experiment Station, has secured positive bene¬ 
fits in 65 per cent, of his trials with' the solid form. 
As the question stands at present in the United States, prac¬ 
tical experiments have shown that the use of pure cultures is at¬ 
tended with much uncertainty. Where the soil is well adapted 
to a leguminous crop, pure culture inoculations have succeeded 
very well, but where the soil conditions are adverse, the simplest, 
