40 BOTANICAL GAZETTE [SEPTE MBER 
any other of the soils analyzed. The order of the soils as to the 
organic matter content is about the same as their order considered 
on the basis of the phosphorus content. It might be that the 
relatively large amount of organic matter in the Chester loam 
and the sassafras silt loam soils is a factor in their productivity. 
Organic matter improves the tilth of soils, adds plant food, and 
has other important effects. 
Their relative ability to produce cereal crops is used as a meas- 
ure of the productivity of the soils. Cereal crops require more 
phosphorus than sulphur. It might well be that, if the production 
of a high sulphur containing crop (alfalfa, for instance) was taken 
as the criterion, the order of the soils in table III would be different. 
Even if phosphorus, rather than sulphur, is at present the limiting 
TABLE U1 
RELATIVE ORDER OF THE FIVE MARYLAND SOILS IN PRODUCTIVITY, SULPHUR, 
PHOSPHORUS, AND IGNITION VALUE 
Soil type Productivity Sulphur Phosphorus |Ignition value 
i=J 
Qu 
et 
o 
5 
ne WN 
WwW Nn 
WWwudb H 
wud H 
factor in these soils, sulphur would no doubt soon become the 
limiting factor if the level of supply of the phosphorus is raised by 
adding phosphorus fertilizers. The sulphur supply is so low that, 
with phosphorus removed as the limiting factor, it might become 
the limiting factor to production. 
Of course it is realized that too great reliance should not be 
placed in a soil analysis, especially such a soil analysis as this, 
where only two of the several elements needed by plants are 
determined. At the most, a soil analysis only shows the total 
amount of plant food present and does not tell anything as to the 
availability of the elements. Also, other factors than plant food 
may be limiting production, but a soil analysis should develop 
some leads, which can be followed up by other methods of attack. 
Since the data show a rather low sulphur content in the few 
Atlantic coast and Gulf coast soils analyzed, it might be of interest 
