Jan. ;;, 1919 



Influence of Salts on Nitric Nitrogen in Soil 127 



RELATION BETWEEN BACTERIAL ACTIVITY AND HIGHER PLANTS 



The results herein reported, together with those published by Dr. Harris 

 (6), make it possible to compare the influence of some of the salts upon 

 the nitrifying powers of a soil with their influence upon the higher plants. 

 This comparison is quite justifiable, for the same soil was used in the ex- 

 periments with seedlings as has been used in the work on bacterial 

 acti\nties. The comparison is made in Table XVI. The results, as re- 

 ported, are the quantities of the respective salts which are necessary to 

 reduce nitrification and the production of dry matter in wheat seedlings 

 to about half -normal. 



Table XVI. — Percentage of various salts in loam soil necessary to reduce nitrification, 

 germination, and dry matter produced in uheai to about half-normal 



Salt. 



Magnesium chlorid. . 

 Magnesium nitrate. . 

 Potassium nitrate. .. 

 Potassium carbonate 



Sodium nitrate 



Sodium carbonate. .. 



Sodium chlorid 



Potassium chlorid . . . 

 Potassium sulphate . 

 MagTiesium sulphate 

 Sodium sulphate. . . . 



Excess re- 

 quired by 

 bacteria. 



394 

 376 

 299 

 562 



130 

 088 



034 

 .048 



251 

 439 

 018 



Four of the salts tested, sodium chlorid, potassium chlorid, sodium 

 sulphate, and calcium chlorid, are less toxic to the nitrifying organisms 

 than they are to wheat seedlings. All of the other compounds are much 

 more injurious to nitrifying bacteria than they are to wheat seedlings. 

 In many cases the wheat seedlings will withstand many times as much 

 of the salt as wll the plant. This is especially noticeable in the case of 

 magnesium nitrate and magnesium chlorid. The plant being able to 

 withstand 70 times as much of this latter compound as will bacteria. 



It is certain from these results that a test of the ammonifying power 

 of an alkali soil gives a better index of its crop-producing power than does 

 a determination of its nitrifying power, for a close correlation was found 

 to exist between the toxicity of many of these salts for ammonifying 

 organisms and wheat seedlings (j). 



RELATIVE STIMULATION OK THE VARIOUS SALTS 



It has been noted repeatedly throughout this work that many of the 

 salts tested increase the accumulation of nitric nitrogen in the soil. The 

 extent of this stimulation and the concentration of the specific salts re- 



