162 BOTANICAL GAZETTE [MARCH 
Other soils contain only a medium amount of soluble salts, and the 
vegetation consists chiefly of alkali-resisting plants. Still other 
soils contain much smaller quantities of soluble salts, and they 
become injurious only when the soil is improperly handled. The 
reclaiming of the heavily charged soils and the maintaining of the 
others in a productive condition are problems confronting the soil 
chemist. These problems can be solved more successfully when 
the laws governing the influence of salts upon the growing plant 
and their action upon the chemical, physical, and biological prop- 
erties of the soil are understood. This study was undertaken, 
therefore, with the hope of obtaining light on some of these laws. 
It was carried on with soils which naturally were productive, but 
TABLE I 
MOLES OF THE VARIOUS SALTS PER I00 GM. OF SOIL REQUIRED TO 
RETARD AMMONIFICATION IN THE SOIL IN UNIT TIME 
Chloride Sulphate Nitrate Carbonate 
Calcite erie ese: 156X10—? 5x10—* 9816-8) LE OTe 
pi oti Nek lee peer wee 625410" | 125x107" Ix107* 6X10—* 
See gee et os eS 125.10" |) O22 x to 25 107% 610-7 
Manganese aie at athe culgs o 125 X10—° 4510-7 Sc 1074 TI X10" 
ee i eS i225 1c < 5x i077 5X10" 6xXio7 
Pata SCL peaierese cn Bice aa SMO UTR x yor" 1x107% 
* Not toxic at 11 X10—3, highest tration tested 
became unproductive through the addition of known quantities 
of various salts. This would give a soil which at first had the same 
physical, chemical, and biological properties, hence any difference 
found must be due to the salt added. 
Using as a measure of toxicity of the various salts that quantity 
which if applied to a definite weight of soil reduces the ammonia 
produced in the soil as compared with a similar untreated soil 
kept under similar conditions, the values reported in table I were 
obtained. The quantity recovered from the soil by leaching was 
also determined, but for this study the quantity applied is used 
for the reason that the direct or indirect action of the addition of a 
specific salt is being determined and not the absolute point of 
toxicity, which undoubtedly will vary es different soils and 
conditions. 
