336 
Journal of Agricultural Research 
Vd. XXIV, No. 4 
(5) The toxicities of all the substances in the first five groups are 
increased by the specific toxicity of sodium carbonate when they are 
added to soil already impregnated with this salt. 
•••• Ca SO 4 L /iLONE 
- /?LdA/£ 
000 Af/ 9 A/(//?£ / 9 /LOA^E 
ColSO^ 
OXC.K Af/^A/m£ 
A/a.2 
000— 
oo.—- 
%CaSO^-f- k-S 
% MmU££ +^S 
i-A/az^ CO3 
Hi CaSO^+h SaLP//(/£\i^g^ CO 3 
4 Ai/fAJURE -h kca S' 
- o 
Wa^ CO^ 
Fig. 13.—Diagram showing the effect on the growth of wheat plants of adding manure, sulphur, and 
gypsum in various proportions to Greenville loam impregnated with sodium carbonate. The maximum 
concentrations of the individual added substances are given in the text. 
( 6 ) Nontoxic quantities of all the substances in the first four groups 
have the power of correcting, to some extent at least, the harmful effects 
of moderate, and in some cases of fairly high, concentrations pf sodium 
carbonate. The salts in the fifth group do not exhibit this property at 
