Jan. 27, 1919 



Influence of Salts on Nitric Nitrogen in Soil 



117 



Table VIII. — Percentage of nitric nitrogen formed in 100 gm. of soil containing 2 gm. of 

 dried blood arid varying amounts and forms of manganese salts 



[The untreated soil is taken as 100 per cent] 



Fraction of molecular weight in 100 

 V gm. of soil. 



None .... 



78X10-' 

 156X10-^ 

 312X10 ^ 

 625X10-^ 

 125X10-' 



25X10-5 

 5X10-" 



I X 10-3 



2X10-3 

 3X10-' 



Amount of 

 manganese. 



P. p. m. 



None. 



4-3 



8.6 



17. 2 



34-4 



68.8 



137-6 



275.2 



550-4 

 I, 100. 8 

 1,651.2 



Percentage of nitric nitrogen formed in presence of- 



Manganous 

 chlorid. 



100. O 

 100. 6 



112. 9 



57-7 

 41.7 



31-9 

 44.2 



55-2 



55-2 



24-5 



4-5 



Manganous 

 sulphate. 



100. O 



113. 2 



100. O 



106. 6 



106. 6 



104. I 



97-6 



loi. 3 



88.7 



80.2 



74-3 



Manganous 

 nitrate. 



100. O 



121. 3 



113. 8 



"3-5 



125.4 



107.9 



79-4 



49-2 



26. 9 



4-5 

 - 17.80 



Manganous 

 carbonate. 



100. o 



91. 2 

 72. 2 



77-8 

 86.3 

 108. 4 

 86.8 

 84.6 

 84.6 

 71. I 

 81.2 



All of the manganese compounds tested are strong stimulants to the 

 nitrifying organisms. The extent of the stimulation and the quantity of 

 the salt required to produce the maximum stimulation varies greatly with 

 the salt used. The sulphate produces its greatest stimulation at the 

 lowest concentration tested, whereas the chlorid is most active at 8.6 

 p, p. m. of manganese, the nitrate at 34.4, and the carbonate at 68.8. 

 Manganous chlorid stimulates the nitrifying organisms greater than it 

 does the ammonifying organisms, whereas with the carbonate the reverse 

 is true. It is quite evident from these results that the stimulation 

 exerted by manganese upon soil organisms is governed by the electro- 

 negative ion, which is combined with the manganese and the specific class 

 of organisms on which it is acting. 



While manganese is at times added to the soil as a soil amendment, the 

 results reported by different investigators vary, some noting a marked 

 stimulation, while in other experiments it is not so pronounced. The 

 data herein reported, together with those previously reported for ammoni- 

 fication, offer a very plausible explanation of the lack of agreement 

 among various reported experiments. 



If we admit that much of the beneficial effect of the manganese on the 

 plant is due to its stimulating influence on the bacterial activity of the 

 soil, thus liberating more available nitrogen, forming organic acids and 

 carbon dioxid, which in turn liberate phosphorus and other elements 

 essential to plant growi;h, we can readily see that its influence upon a 

 plant growing in a soil well supplied with available nitrogen and phos- 

 phorus would not be great. But if the soil contained unavailable plant 

 food, the increased bacterial activity would m.ake more plant food avail- 

 able. This would then be taken up by the growing plant and shown in 

 the increased crop yield. 



