134 Journal of Agricultural Research voi.xvi.no. 4 



Sodium sulphate, sodium carbonate, calcium carbonate, potassium sul- 

 phate, potassium carbonate, and iron nitrate failed to increase the nitric- 

 nitrogen accumulation in a soil. All of the others, however, in some of 

 the concentrations tested acted as stimulants. The extent of the stimu- 

 lation and quantity of salt necessary for maximum stimulation varied 

 with the specific compound. Naming them in the order of increasing 

 efficiency, they are: Sodium nitrate, magnesium sulphate, ferric sulphate, 

 calcium nitrate, potassium nitrate, potassium chlorid, magnesium nitrate, 

 manganous carbonate, manganous chlorid, manganous sulphate, ferric 

 carbonate, magnesium chlorid, manganous nitrate, ferric chlorid, magne- 

 sium carbonate, sodium chlorid, calcium chlorid, and calcium sulphate. 

 The last two increased the nitric-nitrogen accumulation of the soil 67 and 

 97 per cent, respectively. 



Those compounds which are the strongest plant stimulants are also 

 the most active in increasing the nitric-nitrogen accumulation of the soil 

 and it is very likely that the effect upon the plant is due mainly to the 

 action of the compound upon the bacteria which in turn render available 

 more plant food. 



Many of the nitrates caused large losses of nitric nitrogen from the 

 soil; this is due to the stimulation of other species which transform the 

 nitric nitrogen into protein nitrogen and not to denitrification. 



Magnesium nitrate, ferric nitrate, calcium nitrate, and manganous 

 nitrate are very active stimulants of the nitrogen-fixing organisms. In 

 some cases these compounds increased nitrogen fixation many times 

 over that in the normal soil. 



The ammonifying powers of a soil containing alkalis are a better index 

 of its crop-producing powers than are the nitrifying powers. 



LITERATURE CITED 

 (i) Deh^rain, p. p. 



1887. SUR LA PRODUCTION DES NITRATES DANS LA TERRE ARABLE. In Ann. 

 Agron., t. 13, p. 241-261. 



(2) Greaves, J. E. 



1910. EFFECTS OF SOLUBLE SALTS ON INSOLUBLE PHOSPHATES. In JoUT. Biol. 



Chem., T. 7, no. 4, p. 287-319. Bibliography, p. 318-319. 



(3) 



1916. THE INFLUENCE OF SALTS ON THE BACTERIAL ACTIVITIES OP THE SOIL. 



In Soil Sci., v. 2, no. 5, p. 443-480. Literature cited, p. 476-480. 



(4) and Hirst, C. T. 



1917. SOME FACTORS INFLUENCING THE QUANTITATIVE DETERMINATION OF 



NITRIC NITROGEN IN THE SOIL.. In Soil Sci. V. 4, no. 3, p. 179-203, I 

 fig., pi. I. References, p. 200-203. 



(5) Griffiths, A. B. 



1889. A TREATISE ON MANURES. 393 p. London. 



(6) Harris, F. S. 



i915. effect of alkali salts in soils on the germination and growth op 

 CROPS. In Jour. Agr. Research, v. 5, no. i, p. 1-53, 48 fig. Literature 

 cited, p. 52-53. 



