Jan. 6.1923 
Sand Drown , a Chlorosis of Tobacco 
33 
portions of the ash. Roughly, the alkalinity of the soluble ash is a meas¬ 
ure of the potash in combination with citric and malic acids in the sap, 
while the alkalinity of the insoluble portion represents the calcium and 
magnesium salts of these acids existing in solution in the sap. Both the 
sulphate and the chlorid greatly reduce the alkalinity of the insoluble 
ash, that is, the content of the sap in calcium and magnesium citrates 
and malates. The most striking effect, however, is the great increase 
in the sap content of potassium salts of citric and malic acids caused by 
the sulphate, as indicated by the content of soluble carbonate in the ash. 
The chlorid, on the other hand, is wholly ineffective in this respect. 
This difference in the effect of the sulphate and the chlorid on the con¬ 
tent of soluble salts of organic acids is of practical importance, for it is 
known that the potassium salts of citric and malic acids improve the 
combustibility of tobacco (r). 2 On the other hand, the acid calcium 
salts of these acids, which largely make up the grain particles of the cured 
tobacco leaf (5), injure the combustibility, especially if the grain material 
is not definitely aggregated. If the organic acids are intermediate 
products in the respiratory combustion of carbohydrate in the plant, it 
appears that in some way the oxidative processes are less complete in 
the presence of the sulphate than when the potassium is supplied as 
chlorid. It is seen from Table II that addition of the potash salts to the 
soil lowered the calcium content of the plant sap. 
It seemed possible that the unfavorable action of potassium sulphate 
on the vigor of the tobacco plant might be due to injurious increase in 
hydrogen-ion concentration of the cell sap. To test this matter leaves 
were collected at intervals, in the manner already described, from the 
special potash test plots and from other specially treated plots, using 
six plants on each plot for material. The leaf material was not sub¬ 
jected to freezing but was ground in a well-tinned meat chopper and 
the expressed sap was passed through muslin. The hydrogen-ion con¬ 
centration of the saps thus prepared was determined electrometrically 
at room temperature according to the usual procedure. The results are 
presented in Table III. 
Table III. — Hydrogen-ion concentration of cell sap as affected by the sulphate and the' 
chlorid of potassium and other salts 
Hydrogen-ion concentration of sap collected at 
stated intervals. 
Fertilizer treatment of tobacco. 
July 18. 
July 23. 
July 28. 
Aug. 5. 
Average. 
Special potash test plots: 
Pb 
Pn 
Pn 
Pn 
Pn 
Control. 
5 - 47 
5 - 40 
5. 26 
5. 26 
5 * 35 . 
36 pounds K 2 0 per acre as sulphate.. 
5.61 
5 - 6 5 
5 - 47 
5-43 
5 - 54 
36 pounds K 2 0 per acre as chlorid... 
5 - 43 
5 - 33 
5 - 29 
5. 28 
5 - 35 
80 pounds K 2 0 per acre as sulphate.. 
80 pounds KjO per acre as chlorid 
S’ 50 
5 * 63 
5 * 52 
5*46 
5 - 55 
5-^4 
5 - So 
5 - 46 
5 - 29 
5 - 4 & 
? ReJerence is made by number (italic) to ” Literature cited,” p. 40 , 
