ii6 



Journal of Agricultural Research 



Vol. XVI. No. 4 



Table VII. — Percentage of nitric nitrogen formed in lOO gm. of soil containing 2 gnt. 

 of dried blood and varying amounts and forms oj magnesium salts 



[The untreated soil is taken as loo per cent) 



Fraction of molecular weight in loo 

 gjn. of soil. 



Amount of 

 magnesium. 



Percentage of nitric nitrogen formed in presence of — 



Magnesium 

 chlorid. 



Magnesium 

 sulphate. 



Magnesium 

 nitrate. 



Magnesium 

 carbonate. 



None. . . . 



78x10-7 

 I56XIO-7 



312X10— 7 

 625x10-7 

 125X10—* 



25X10-* 

 5XI0-* 



lXlO-3 



2x10-3 

 3x10-3 



p. p. m. 



None 

 1.9 



3-8 

 7.6 



15.2 



30-4 



60.8 



121. 6 



243.2 

 486.4 

 729. 6 



100. o 

 67.7 

 58.0 

 68.5 



55- o 



97.1 



123.2 



84-5 

 78.6 

 26. 5 

 II. 8 



100. o 

 95-2 

 96. 2 



101. 2 

 87.1 

 88.7 

 94.6 

 90.4 

 82.9 

 63-3 



59-6 



92.9 



8S-7 



106. 5 



87.0 



95-7 

 65. 2 



43-5 



5-0 

 -354- 7 



100. o 

 90.4 



97-7 

 108. I 

 136. 1 

 119. 8 

 140. 7 

 loi. 2 

 116. o 

 72.7 

 51-7 



Magnesium carbonate reaches its highest stimulation at a concentration 

 of 25 X io~^ mole, and at a concentration of 3 X io~^ mole the ammonify- 

 ing powers had been reduced to one-half normal almost the same as was 

 the case with the calcium carbonate. 



It is indeed interesting to note that this soil, which already contains 

 over 8 per cent of magnesium carbonate, has its nitrifying powers in- 

 creased by the addition of magnesium carbonate. This would lend sup- 

 port to the idea promulgated in the last section that the depressing effect 

 of the calcium carbonate is due to its changing of the lime-magnesia 

 ratio in the soil. 



All of the magnesium salts are peculiar in that at the lower concentra- 

 tions they are toxic, but that at higher concentrations they are stimu- 

 lants. This peculiarity is especially noticeable in the case of magnesium 

 chlorid. 



Both the chlorid and sulphate were toxic in all but one of the concen- 

 trations tested. The sulphate and carbonate of magnesium at the 

 highest concentration tested reduced the nitrifying powers to about 

 one-half normal, while the same concentration of the chlorid reduced it to 

 less than one-eighth normal. A similar concentration of the nitrate 

 caused a rapid disappearance of the nitrate from the soil. 



It is quite evident from these results that the determining factor in the 

 action of calcium or magnesium salts upon the nitrifying powers of the 

 soil is the electro-negative ion. 



INFLUENCE OF MANGANESE SALTS 



The compounds used in this series were manganous chlorid, manganous 

 sulphate, manganous nitrate, and manganous carbonate. The results so 

 obtained as the average of a great number of closely agreeing determina- 

 tions are given in Table VIII. 



