204 Mr. Hall, Dr. Miller, and Mr. Gimingham. [Dee. 19, 
To one-half of each of the plots, 2000 lb. per acre of ground quicklime 
was applied in January, 1903, the application being renewed in 1907. 
Samples of soil taken in October, 1906, from the unmanured_ Plot 3, 
and from Plot 11-1, which receives the largest amount of ammonium salts, 
showed the following proportions of calcium carbonate, as calculated from 
the carbon dioxide evolved on treatment with hydrochloric acid. 
Depth. Plot 3. Plot 11-1. 
inches. 
o— 9 0-516 0 -16* 
10—18 0-206 0°151 
19—27 0 -092 0-106 
28—36 0 087 0°141 
B. Examination of the Soil for the Nitrifying Organism. 
From 0:2 to 1 gramme of the soil under examination was added to 100 c.c. 
of a culture solution made up as follows :— 
Ammonium ‘sulphate \..c22-- ese. 0-5 gramme per litre 
Monopotassium phosphate ......... 0:25 me 
Maenesium sulphate (cryst.)........ f Usk . 
Soditmaschloride se. eee. 0°5 
Ferrousisulphate > erence... ce 0-1 F. 
together with about 0°2 gramme of a mixture of sterilised magnesium and 
calcium carbonate. The solutions were in Erlenmeyer flasks, and had pre- 
viously been sterilised in the usual way; they were then incubated for at least 
a month at a temperature of 30°, the contents being gently shaken two or 
three times during that period. At the end an examination of the clear 
liquid was made for nitrates with diphenylamine, for nitrites with meta- 
phenylene-diamine, for ammonia with Nessler’s reagent. 
The soil samples were prepared as follows :— 
In four series holes were dug in the field and sterile brass cavenl 1 inch 
in diameter were forced into the sides, after breaking away some soil 
to expose a clean surface. The tubes were carried to the laboratory, the 
contents forced out into dishes and partly dried over strong sulphuric acid, 
suitable precautions being taken to avoid external contamination. The | 
partly dried soil was then roughly powdered and stones removed by passing 
through a 1 mm. sieve, sieve and mortar being sterilised each time. By a 
suitable spoon a quantity found by trial to be approximately 0:2 gramme 
* Since the above was written the authors have seen reason to suppose that some of 
the carbon dioxide, evolved on treating soils of this character with hydrochloric acid, 
comes from the organic matter. Several other processes agree to make the calcium 
carbonate in the surface layer amount only to 0°04 per cent.—Wote added March 19, 1908. 
