34 



Journal of Agricultural Research 



monium carbonate the production of dry matter was stimulated by low 

 concentrations of the salts. The growth of plants was not greatly reduced 

 by the sulphates even in relatively high concentrations, while with the 

 chlorids the yield dropped very rapidly and was practically nothing 

 where the concentration was above 4,000 p. p. m. 



Figure 34 shows the dry matter produced by different kinds of crops 

 in soils containing sodium chlorid, sodium carbonate, and sodium sulphate 

 in concentrations from 1,000 to 10,000 p. p. m. Com gave by far the 

 largest quantity of dry matter, but it was probably as much affected by 

 the salt as any other crop. The yield was reduced from above 0.6 gm. 

 per glass with no salt to less than o.i gm. per glass with a concentration 

 of 10,000 p. p. m. Canada field peas produced a large quantity of dry 



1,000 2,000 3,000 4,000 5,000 6,000 7,000 

 Concentration of salts in p. p. m. 



9,000 10,000 



Fig. 34. — Curve showing the effect of concentration of salts on the dry weight of plants from seeds of various 

 kinds. Average for sodium chlorid, sodium carbonate, and sodium sulphate. 



matter, but they were also greatly affected by the concentration of salt. 

 Alfalfa gave the least total yield under all conditions. 



The effect of the individual salts on the yield of the various crops is 

 brought out in figure 35. The yield of all crops was highest with sodium 

 sulphate and lowest with sodium chlorid. With most crops it was only 

 about half as great with sodium chlorid as with sodium carbonate. 



DAYS TO COME UP 



During the experiments a count was made each day of the number of 

 plants that appeared above the surface of the soil, and from these figures 

 a determination was made of the average time required for the plants 

 in each glass to come up. The average results are in some cases mis- 

 leading, because with toxic salts no plants genninated in the high con- 

 centration, and the averages were determined from the plants that came 



