VOLUME LXXIII NUMBER 3 
THE 
BOTANICAL GAZETTE 
March 1922 
INFLUENCE OF SALTS ON BACTERIAL 
ACTIVITIES OF SOIL 
J. E. GREAVES 
Salts occurring naturally in soils and those applied to them 
in various operations influence the number, species, and activity 
of the soil microflora. These factors in turn are reflected by yields 
obtained. Some substances applied to a soil may serve as food 
for the growing plant; others increase plant growth indirectly. 
This latter effect may be due to the changing of the physical, 
chemical, or bacterial properties of the soil. The substance may 
alter the physical properties of the soil to such an extent that the 
bacterial flora is modified. This in turn may increase or decrease 
the available plant food of the soil. Other substances may react 
chemically with constituents within the soil, and in so doing 
‘liberate nutrients which may be utilized directly by the growing 
plant (24). Again, they may directly modify the microflora and 
microfauna of the soil both as to numbers and_ physiological 
efficiency. In some cases all three changes may be wrought by 
the same salt. In each case the soil is so changed that its crop- 
producing power is modified. The question arises, therefore, as to 
what effect this or that fertilizer or soil amendment is going to 
have upon the bacterial activity of the soil. Furthermore, there 
are millions of acres of land which contain varying amounts of 
soluble salts. Some of these soils contain such large quantities 
of the so-called “alkalis” that no vegetation grows upon them. 
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