Jan. 6. 1923 
Sand Drouiij a Chlorosis of Tobacco 
37 
toes. Considerable attention also has been given to the toxic effects of 
magnesia compounds when present in excess, especially since Loew 
developed his well-known theory of optimum lime-magnesia ratios for 
crop plants (4). 
It seems clear that on many soils it is essential for normal development 
of the tobacco plant that the fertilizer carry a certain minimum quantity 
of magnesia, especially when the fertilizer contains soluble sulphates. 
Preliminary observations indicate that corn and cotton and probably 
other crops have similar requirements. The exact needs of the tobacco 
crop will require considerable study, since both the yield and the quality 
of the product are involved. The combustibility of tobacco is affected 
adversely by salts of magnesia, and it appears that the moisture-holding 
properties, and therefore the elasticity, of the leaf are influenced by the 
magnesia supply. The highly injurious effect of magnesium deficiency 
on the color of the leaf has already been discussed. Hence, it seems likely 
that any considerable excess of magnesia, as well as a deficiency, must be 
avoided for best results. 
Detailed data of plot yields with tobacco in different localities for a 
period of years comparing the action of sulphate and chlorid of potash, 
which involve the effects of magnesium deficiency, are reserved for publi¬ 
cation elsewhere. It will suffice to present here the results obtained at 
Oxford, N. C., in 1920, as illustrating the striking effect of magnesium 
deficiency on the market value of the crop. The detailed fertilizer treat¬ 
ment of these plots has already been described. One-half of each plot 
received ground limestone containing magnesia applied broadcast in the 
fall of 1919 at the rate of 1 ton per acre. The yield and value of the 
tobacco on each plot are shown in Table V. 
Table V.— Yield and value per acre of tobacco receiving sulphate and muriate of potash, 
unth and without addition of ground limestone , Oxford, N. C., IQ20 
Potash (K 2 O) added as fertilizer. 
| Yield of tobacco. 
Value of tobacco. 
Without 
lime. 
With 
lime. 
Without 
lime. 
With 
lime. 
Pounds. 
Pounds. 
None. 
33° 
450 
$27 
$38 
12 pounds per acre, as sulphate. 
260 
660 
33 
12 pounds per acre, as muriate. 
520 
640 
67 
126 
24 pounds per acre, as sulphate. 
480 
620 
47 
93 
24 pounds per acre, as muriate. 
620 | 
| 820 
107 
147 
36 pounds per acre, as sulphate. 
600 
640 
88 
90 
36 pounds per acre, as muriate. 
7S0 
780 
IJ 7 
80 pounds per acre, as sulphate. 
700 
58c 
78 
107 
80 pounds per acre, as muriate. 
800 
920 
”5 
218 
Considering only the treatments without lime, it is seen that the muri¬ 
ate gives far better results than the sulphate; and the difference becomes 
most striking with the intermediate rates of application. The injury in 
quality of the tobacco from the use of sulphate is proportionately greater 
than the reduction in yield as compared with the muriate. Evidence has 
.already been given that addition of magnesia fully overcomes the unfa- 
