Aug. 28, 191C 



Effect on Plant Growth of Sodium Salts 



861 



Table II. — Results of experiment 2 {1914), giving the quantity of sodium carbonate added 

 to the soil, the quantity finally recovered as carbonates, the number of plants, and the 

 combined weight produced in each case 



Series No. 



De- 

 crease 



in 

 yield 

 from 

 check 



pot. 



3- 

 4- 



5- 



6. 



7- 



8. 



9 



Per ct. 



O 

 IO 



33 

 45 

 7 1 

 85 

 94 

 90 



97-5 



1 In excess of sodium bicarbonate present at beginning of experiment. 



The results of experiment 2 are in close accord with those of No. i, 

 although the decrease in yield was not quite so rapid. The apparent 

 loss of carbonates — that is, the difference between the amount added 

 and that recovered — was slightly greater. It is noticeable that in both 

 experiments the percentage of sodium bicarbonate recoverable did not 

 increase materially with the percentage of carbonate added, while there 

 was a fairly consistent increase in the percentage of carbonate recovered. 

 Furthermore, it will be observed that the decrease in yield follows the 

 increase in total carbonates recovered more closely than the increase 

 in carbonate added to the soil. 



The results of experiment 2 are shown graphically in figure 2, in which 

 the same arrangement of symbols is used as in figure 1 . 



Experiment 3. — This experiment was undertaken for the purpose 

 of comparing the toxic effect of sodium carbonate on the growth of wheat 

 seedlings in two very different types of soil. The first of these was a 

 rich loam soil from an old alfalfa field on the Truckee-Carson Irrigation 

 Project, and the second was beach sand obtained from Monterey, Cal. 

 The experiment was conducted in the summer of 191 5. Duplicate sets of 

 pots were used in each case. After the salt had been added to the pots, 

 the moisture content was kept at 1 2 per cent in the sand and 1 5 per cent 

 in the loam. This arrangement had the disadvantage of making the con- 

 centration of the soil solution different in the two soils, but it was con- 

 sidered necessary because 15 per cent of moisture in the sand would 

 have kept it too wet, and less than 15 per cent in the loam soil would 

 not have been sufficient for the best growth of the plants. 



