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of the pots were found acid, but all were slightly alkaline, as normal 
soils should be. So the cause of the dying of the plants on pots 
405 and 406 is unexplained. It was not due to acidity of the soil 
and it seems that it could not be due to lack of plant food, for there 
were free nitrates present and the corresponding pots unsterilized 
showed no lack of plant food. 
The following investigation 1 on the effect of soil sterilization on 
the development of plants bears directly on the point under dis- 
cussion. It was made by C. Schulze of Germany. He made pot 
experiments with field, meadow and garden soil. The crops grown 
were oats, mustard, peas, buckwheat and grasses. One pot of each 
series was untreated, one was sterilized for one hour at 125°C. be- 
fore fertilizing, one sterilized the same after adding the fertilizers, 
and a fourth was sterilized at 100°C. for 18 hours. During steriliza- 
tion, there was found to be a formation of more or less injurious 
decomposition products and also a release of otherwise non-avail- 
able nitrogen. The addition of lime counteracted the injurious ef- 
fects of the decomposition products. In general sterilization 
seemed to retard growth for a time, but later the plants became 
more vigorous in the sterilized pots, often exceeding in total growth 
those in the untreated pots. In most cases there was an increase 
in the total plant product which was attributed to sterilization. 
This agrees exactly with my results and it seems safe to con- 
clude that the bacteria in the soil did not aid in the better growth 
of the clover. They may have, and in fact seem to have a great deal 
to do with elaboration of plant food and the probabilities are that 
a soil kept sterile, would soon become unproductive, but it also 
seems true that the loss of the bacteria would not be felt the first v 
few months or during the production of the first crop. If that is 
the case, the greater number of the bacteria in the manured pots, 
41 and 46, noted above over the check No. 44, was due to the same 
cause as the better clover, but the larger number of bacteria were 
not responsible for the larger clover. That is the question we 
were working on. If this may be considered settled, then the con- 
clusion is that bacteria in no way were responsible for the bene- 
ficial action of the manure on the growth of the clover, for in the 
first place it was shown that sterile manure was as beneficial as the 
unsterilized, and in the second place it was shown that when the 
whole pot was sterilized, the crop did not suffer but was even a 
little better. 
. Abst. Experiment Station Record 18, p 542. 
