1907.) Nitrification in Acid Sols. | 207 
Two kilogrammes of an air-dried sample of the soil from Plot 11-1 were 
extracted with successive quantities of hot water and the extract concentrated 
_ to a volume of 500 cc.; 50 ce. portions of this were placed in the usual 
flasks for nitrification, 5 c.c. of a 1-per-cent. solution of ammonium sulphate 
was added, and each was seeded with 5 cc. of a cold water extract from 
a garden soil in a good state of fertility. The object was to ascertain if the 
acidity of such a medium, which would represent the solution in the soil 
when it contains 25 per cent. of water, would be sufficient to inhibit 
nitrification after a fresh stock of the organisms had been supplied. The 
extraction of the dried soil had, however, not been very effective, and 
the initial acidity was only equivalent to 0°6 cc. of n/10 alkali, or a little 
more than one-thousandth normal. In the check flasks the acidity was 
removed by the addition of a mixture of calcium or magnesium carbonates, 
and they were all incubated for three weeks at 30° C. Determinations 
were made of the nitrates before and after incubation, with the following 
results :-— 
50 cc. Soil Extract+ 5 c.c. Soil Extract +5 c.c. 1-per-cent. (NH4)2SO4. 
Nitrogen as nitrates. . 
milligrammes, 
1, 2,3 No calcium or magnesium carbonate, incubated ............ 0°95 
4, 5,6 With calcium and magnesium carbonates, incubated ...... 2°38 
7,8 INO DRM CUWATER) eRe psdedsccsatey alvdes Siviccededoheonennpned bodes aes 1°25 
There was no formation of nitrates except when the acid had been 
neutralised by the calcium and magnesium carbonates. In 1, 2, and 3 weak 
growths of mycelium were visible, but none in the neutral extracts, 4, 5, 6. 
In a further experiment fresh soil was brought from Plot 11-1 and 
extracted rapidly with cold water; the extract had a slight acidity, equal to 
0-6 c.c. n/10 acid per 100 cc. Portions of 50 c.c. were taken and 5 cc. of 
1-per-cent. ammonium sulphate were added to each; in some cases the 
extract alone was incubated for three weeks, with or without earthy 
carbonates; in others, 5 c.c. of a garden soil extract prepared as before was 
added to introduce the nitrification organisms. Nitrates were determined 
after a month’s incubation, and in the checks before starting, with the 
following results :— } 
50 c.c. Soil Extract +5 c.c. 1-per-cent. (NH,z)2SOx. 
Nitrogen as nitrates. 
milligrammes. 
1 and 2 ING SIGUA LOR 5 2. . oshe pans ce ote + ss cduemenoMn agate sd ornae edb ane ets 0°25 
3 ,, 4 No calcium and magnesium carbonate, incubated ......... 0°23 
5 , 6 + Calcium and magnesium carbonate, incubated ......... 0°31 
Der Ss +5 c.c. garden soil extract, no calcium and magnesium 0°39 
carbonates, incubated 
Pes LO +5 c.c. garden soii extract, + calcium and magnesium 6°83 
carbonates, incubated 
