Jan. 6,1933 
Sand Drown , a Chlorosis 0 } Tobacco 
30 
sand drown, and heavier applications probably would further increase 
the effectiveness of both the sulphate and the chlorid of potassium by 
removing magnesium deficiency as a limiting factor. It is of interest to 
note that Wheeler and Hartwell (6) found a marked increase in content 
of magnesium but not of calcium in both red clover and common sorrel 
(Rumex) grown on soil which had been limed. The value of liming 
in overcoming sand drown has been confirmed in other tests involving 
the use of various potash salts containing different percentages of mag¬ 
nesia. In all cases sand drown associated with the use of the purer 
potash salts was entirely prevented by applying dolomitic limestone^ 
Thus, to the various functions in improving soil productiveness which 
have been ascribed to liming must be added that of preventing or cor¬ 
recting magnesium deficiency. Again, it has been shown that one of the 
harmful effects which may result from the use of ammonium sulphate 
as fertilizer without liming is to cause a deficiency of magnesium, and 
this injurious effect may be remedied by use of magnesium salts as well 
as by liming. It is to be noted that the value of limestone in supplying 
small quantities of magnesia has little or no connection with the theory 
of optimum lime-magnesia ratios. 
NEW METHOD FOR CONDUCTING POT CULTURES IN THE STUDY OF 
FERTILIZER PROBLEMS 
It is well known that it is difficult in most cases to harmonize the results 
of pot tests conducted under accurately controlled conditions with results 
obtained in the field. Experience obtained in the study of sand drown 
has emphasized two important particulars in which the two types of 
experimentation usually differ. In the first place, chemically pure salts 
are generally used in pots cultures while in the field pure fertilizer salts 
are practically never used. In the second place, in conducting pot tests 
precautions are usually taken against any loss of material through drain¬ 
age, while in the field more or less leaching invariably occurs. By com¬ 
mon consent investigators and farmers alike constantly speak only of 
the three elements, nitrogen, phosphorus, and potassium (with occasional 
reference to sulphur) in discussing fertilizers. In practice, however, the 
use of so-called complete fertilizers regularly involves applying to the 
soil at least six essential elements, namely, nitrogen, phosphorus, potas¬ 
sium, sulphur, magnesium, and calcium. It is not surprising, therefore* 
that in ordinary fertilizer usage the need of the three last-named elements 
does not become apparent. It has been shown, however, that the 
result is very different, at least in the case of tobacco, when fertilizer 
salts of high purity are used. On sandy soils subject to severe leaching 
and containing little organic matter it should not be surprising to find a 
deficiency of magnesium or sulphur or calcium as well as of nitrogen* 
phosphorus, or potassium. Sand drown seems to furnish a convincing 
illustration. 
The satisfactory results obtained in inducing sand drown in pot cultures 
have suggested that by giving due consideration to commercial fertilizer 
salts with respect to all of the six elements mentioned and by providing 
for leaching effects pot cultures can be made to yield results more in line 
with field experience. The essential feature of the leaching process, 
consists in the use of nutrient solutions, complete and with one or more 
elements omitted, as desired, instead of distilled water for producing 
leaching effects. The leaching can be pushed as far as desired without 
