INFLUENCE OF SOIL ALKALI ON BACTERIA 193 



These results were obtained by adding the given quantity of 

 the respective salt to a highly calcareous loam and then observing 

 the concentration at which stimulation was greatest. This would 

 differ probably with the texture and organic content of the soil. 



Here we have a marked acceleration of the speed with which 

 protein is transformed into ammonia when some alkalies are 

 added to a soil. When 1,908 pounds of sodium carbonate are 

 added to this soil, ammonifi cation is increased 10 per cent. The 

 other salts stimulate to a less but still an appreciable extent. This 

 would give greater quantities of ammonia for the nitrifiers to 

 work upon, and it is seen that they are stimulated to even a 

 greater extent than are the ammonifiers. 



All of the salts also increase nitrogen fixation; hence, the 

 addition of some alkalies to a soil increases not only the available 

 but also the total nitrogen supply of the soil. The increased 

 bacterial activity would liberate more phosphorus and potassium 

 for the plant. Calcium sulfate or gypsum is especially active in 

 increasing nitrification, and hence increases .proportionately the 

 plants growing on that soil. The dealer in gypsum often takes 

 advantage of this fact in advertising his materials by writing the 

 word PLASTER with a heavy application of the material in 

 large letters on a cultivated field in view of the public road. In 

 the larger greener growth of grain crops or grasses the word 

 PLASTER can be read by the passersby. In this way the farm- 

 ers are induced to use gypsum or land plaster. This, however, is 

 usually a stimulant, and if the landowner will continue to apply 

 the material year after year where the word was first written, the 

 time will come when it cannot be read. If he continues the ap- 

 plication long enough ultimately one may again read the word 

 PLASTER^ but this time the grain composing the word would 

 be inferior to that surrounding it. Moreover, where the plaster 

 has been applied the physical properties of the soil would be 

 found to be bad. 



Common salt is also often used as a crop stimulant. This acts 

 mainly by increasing bacterial activity and with the exception of 

 the true gain in nitrogen it is also a stimulant. Now, it may be 



