124 EXPERBIENT STATION. [Jan. 



and allied forms of animal life which prey upon micro- 

 organisms. 



It would be unjust for us to aftirm what might take place in 

 the soils of England or those on the continent, and it is to be 

 assumed that the soil and climate, as well as the biological con- 

 ditions, are diilcrent from those here; nevertheless, we arc con- 

 vinced that the biological theory does not hold in the soils we 

 have experimented with for years, and as far as we are able to 

 determine it possesses no significance. The matter, however, will 

 be discussed in the following article prepared at our suggestion 

 by Messrs. Smith and Lodge. These investigations were made 

 imder our direction in our laboratory during 1910 and 1911, 

 when the men were taking senior work in the college, and prove 

 to our satisfaction that protozoa, at least in our soil, have little 

 or no part in accounting for the increased number of bacteria in 

 our soils, although we cannot affinn that they do not play a more 

 important role in England and elsewhere.^ 



The stimulating effects which sterilized soils have upon bac- 

 teria are chemical in nature, and so far as we can determine 

 with our soils biological factors exert no influence in this respect. 

 j\Iost observers, we believe, agree that ammonia is given off from 

 sterilizing soils, owing apparently to dentrification, and in this 

 connection we might relate that in some cases whei'c horse ma- 

 nure was applied freely and sterilization followed we noted that 

 if certain plants, such as tomatoes, were transplanted in the soil 

 too soon after the sterilizing had been done, their leaves would 

 present symptoms of ammoniacal burning. 



The sterilizing of soils has been carried on very extensively 

 for some years in this country, particularly in greenhouses, and 

 we have had opportunities to observe various crops growing in 

 many acres of treated soil. Tn practically all cases moist heat, 

 that is, steam, is employed for this purpose, although hot water 

 has been used with practically the same results. There are, as 

 might be expected, a variety of opinions as to the effects which 

 stimulation has upon plants, since a large variety of soils have 

 been treated, and the crops have been groAvn under very variable 

 conditions, ^[oreover, as has already been stated, some crops 



' Mr. David Larsen, who ia associated with the Hawaiian Sugar Planters' Experiment Sf^tion 

 in Honolulu, informs me that protozoa are quite abundant in Hawaiian soils, and that carbon 

 bisulfid applied to the soils there acts as a great stimulus to crop production. 



