192 



BACTERIA AND SOIL FERTILITY 



ing from a fertile field to an alkali plot! The one is covered 

 with a luxuriant growth of healthy vegetation and the other with 

 a scant growth of salt grass or shadscale. Or, if the alkali be- 

 comes too concentrated, the land is a barren waste. A similar 

 condition is found to exist on examining the microflora of the 

 two soils. The fertile soil contains millions of microorganisms 

 in every gram. There is an abundance of nitrifiers, ammonifiers, 

 azofiers, cellulose ferments, and all the decay bacteria, whereas 

 the molds are conspicuous by their absence. On examining the 

 alkali soil we find the millions have dwindled into thousands, and 

 in place of the rich variety of a fertile soil there are only a few 

 of the more hardy species, and the molds often predominate. 



Stimulation of Bacteria by Alkali, — Small quantities of most 

 poisons when administered J.an act as a stillant, and it is 

 only when the dose becomes larger that the poisonous action is 

 perceptible. This appears to be a universal law, holding for man, 

 animals, and plants including microbes, for it is found that 

 when small quantities of alkali are added to a soil the bacterial 

 numbers and activity increase. The extent of this increase varies 

 with different microorganisms and also with the kind of alkali. 

 If we consider the transformation going on in the untreated soil 

 as 100 we then have the following for alkali-treated soils: 





Ammonification 



Nitrtfication 



Nitrogen 

 Fixation 





Lbs, per 





Lbs. per 





Lh, per 





Salt 



Acrefor 



Ammonia 



Acrefor 



Nitrates 



Acre/or 



N. 





Highest 



Produced 



Highest 



Produced 



Highest 



Fixed 





Stimula- 



% 



Stimula- 



% 



Stimu- 



% 





tion 





tion 





lation 





Sodium carbonate 



1,908 



110 



No stim 



ulation 



1,908 



no 



Sodium nitrate 



i>763 



108 



281 



loi 



191 



104 



Calcium sulfate 



612 



104 



9,800 



197 



4,900 



104 



Magnesium sulfate 



270 



105 



137 



lOl 



68 



104 



Sodium chlorid 



% 



1 06 



2,000 



H3 



526 



109 



Magnesium chlond 



28 



lOI 



850 



123 



1,700 



103 



No salt 







100 







100 







100 



Calcium chlorid 



No stimulation 



4,000 



168 



61 



102 



Sodium sulfate 



No stimulation 



No stim 



ulation 



1,000 



108 



