Jan. 6,19*3 
35 
Sand Drown , a Chlorosis of Tobacco 
of potassium, and since sand drown was present on the plants receiving 
the sulphate the disease can not be due to calcium deficiency. The in¬ 
creased content of soluble sulphate, however, is undoubtedly significant 
No evidence of soluble oxalates could be found in the sap from leaves 
affected with sand drown. 
MAGNESIUM DEFICIENCY THE CAUSE OF SAND DROWN 
As previously stated, the effectiveness of magnesium sulphate in pre¬ 
venting sand drown in field tests at Oxford while other sulphates greatly 
aggravated the trouble suggested that lack of an adequate supply of 
magnesium might be the cause of the trouble. Pot tests soon proved this 
to be the case. The cultures were conducted in 12-quart galvanized-iron 
buckets with perforated bottoms, using sassafras fine sandy loam soil 
from Prince Georges County, Md., and in some cases the Durham sandy 
loam soil from the Oxford (N. C.) Tobacco Station. As a complete 
nutrient solution for the cultures a mixture of 10 gm. sodium nitrate, 5 
gm. monocalcium phosphate, 5 gm. potassium sulphate and 5 gm. mag¬ 
nesium sulphate was dissolved in 10 liters distilled water. In some cases 
potassium chlorid was substituted for the sulphate and ammonium 
nitrate was used in place of the sodium salt. For one series in each test 
the magnesium sulphate was omitted from the nutrient solution. To ac¬ 
centuate the effect of omitting magnesium the plan was adopted of water¬ 
ing the plants with the nutrient solution instead of distilled water, the 
solutions being added in considerable excess so as to cause a leaching 
.effect. This plan proved to be quite successful. Where magnesium 
was omitted from the solution sand drown quickly appeared. A typical 
case in the advanced stage is shown in Plate 4. It will be seen that the 
leaves have lost nearly all color and hang limp, the cells having lost their 
turgidity. It is to be noted, however, that seed formation was success¬ 
fully accomplished and the chlorotic leaf tissue remains alive for many 
days. Under favorable conditions the disease may be induced by apply¬ 
ing the fertilizer salts (with magnesium omitted) to the soil before trans¬ 
planting and avoiding any leaching action in watering the plants, as is 
shown in Plate 5. Naturally, the symptoms are less severe than when 
leaching is employed. When the disease has not progressed too far it is 
readily cured by addition of magnesium to the soil. A case of this sort 
is shown in Plate 6. The plant at the right, affected with sand drown in 
severe form, to which magnesium sulphate had been subsequently added 
was rapidly recovering at time of photographing. Thus, while soluble 
sulphates generally will greatly aggravate sand drown, sulphate of mag¬ 
nesium both prevents and cures the malady. It seems proper, therefore, 
to consider lack of an adequate supply of magnesia as the primary cause, 
whatever may be the internal processes involved. On the other hand, 
the importance of an increased supply of soluble sulphate as an inciting 
factor should not be overlooked. In other words, the ratio of magnesia 
to soluble sulphate seems to be of prime importance. 
SAND DROWN CONTRASTED WITH OTHER TYPES OF CHLOROSIS 
The tobacco plant with its extensive foliar expanse is well adapted to 
the study of pathological symptoms such as those characteristic of sand 
drown; and the plant, in fact, is subject to several types of chlorosis. Of 
special importance in this connection is the chlorosis due to potash hun- 
, ger. In typical cases, the symptoms of potash hunger are readily 
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