no Journal of Agricultural Research Voi. xvi,no.4 



sterile distilled water and then quantitatively determining the amount 

 present. In those cases in which the analysis showed the concentration 

 wrong, it was corrected, so that we have a definite knowledge of the 

 quantity of salt added to the soil, as the varying results reported by 

 different investigators can in many cases be interpreted by the unknown 

 variation in salts added. The solution thus prepared was then added 

 to the soil in such quantities as to make the am.ount of the anion and of 

 cation the sam^e and directly comparable the one v/ith the other. The 

 comparatively insoluble salts, calcium carbonate, calcium sulphate, etc., 

 were carefully weighed and intimately mixed with the soil. The ar- 

 ranging of the v/ork in this order gives us as nearly absolute results as 

 can be obtained by the present bacteriological methods, and at the same 

 time gives us directly comparable results, which after all is what we 

 have to look for in this work. 



The salts tested were the chlorids, nitrates, sulphates, and carbonates 

 of sodium, potassium, calcium, magnesium, manganese, and iron. 



INFLUUNCI3 OF SODIUM SAINTS 



The compounds used in this series were sodium chlorid, sodium sul- 

 phate, sodium nitrate, and sodium carbonate. They were in concen- 

 trations such that equivalent quantities of sodium in the various forms 

 could be directly compared. The strengths varied from o to 1,380 

 p. p. m. of soil, and represented the actual proportion of sodium in the 

 various forms applied to the soil. The results are reported as percentage, 

 considering the nitric nitrogen produced in the untreated soil in each 

 case as 100 per cent. This method of reporting the results makes them 

 more directly comparable than if stated as milligrams of nitric nitrogen 

 formed in 100 gm. of soil. The average nitrifying power of the untreated 

 soil was 53 mgm. of nitric nitrogen per 100 gm. of soil. The results 

 are given in Table II, and in every case are the average of at least four 

 and sometimes of several times this number of closely agreeing deter- 

 minations; hence, they should represent very closely the comparative 

 influence of the various sodium salts upon nitrification. 



Sodium chlorid is the only one of the sodium salts tested which in- 

 creases the accumulation of nitric nitrogen in the soil. In this regard 

 nitrification differs widely from ammonification, for in the latter both 

 sodium nitrate and sodium carbonate stimulate. However, sodium 

 chlorid is a much more active stimulant of the nitrifiers than it is of the 

 ammonifiers, and it stimulates in much higher concentration, being the 

 most. active when the soil contains 230 p. p. m., and is not toxic until the 

 quantity in the soil exceeds 460 p. p. m. The toxicity rapidly increases 

 above this concentration, and at a concentration of 1,380 p. p. m., the 

 nitric nitrogen present had been reduced to 16.4 per cent of what it was 

 in the original soil. 



