1922] WOODARD—SOIL FERTILITY 103 
the second clover crop, and Mr. TuomMey an increase in alfalfa. 
Neither of these men weighed the hay, so the results are not quan- 
titative. Mr. SHArRpP’s field, from which sample 30 was taken, is 
low in sulphur and high in phosphorus, but it showed evidences of 
being farmed hard, and was evidently low in nitrogen, which was 
probably the limiting element for a non-leguminous crop like 
tobacco. Mr. Fowter’s soil, no. 32, has 0.0250 per cent sulphur 
and 0.1727 per cent phosphorus, equivalent to 500 pounds of sul- 
phur, and 3454 pounds of phosphorus, in the surface soil; so sulphur 
was probably the limiting element for clover. Mr. Tuomey’s field, 
sample 34, had 6814 pounds of phosphorus, the highest of the 
samples analyzed. This sample also contained small fragments of 
limestone, so that there was an abundance of lime. On the 
other hand, the sulphur content, 626 pounds, although higher than 
in many samples, is probably rather low for a plant like alfalfa, 
which uses such large quantities of sulphur. 
These results are not conclusive, but it seems probable that 
sulphur may be a limiting element on some of these soils, and that 
gypsum is a satisfactory source of supply for this element. More 
field experiments are necessary in the humid part of the United 
States, and great care in conducting these experiments is necessary 
if satisfactory results are to be obtained. Experiments should be 
conducted through several years to avoid weather conditions, which 
may be the limiting factor in some years. On some soils drainage 
is necessary, and no fertilizer treatment will have any effect until 
this is done. Most soils in the humid part of the United States 
are acid. A large part of them are so acid that liming is necessary 
before any other treatment is effective, especially for leguminous 
crops. Table I shows a high phosphorus content in some of the 
soils reported in this paper, but those are exceptional soils. Asa 
general rule soils are deficient in phosphorus, and farmers report 
increases in crop yields for the use of acid phosphate. It is impos- 
sible, however, to tell how much of the increase is due to the phos- 
phorus and how -much to the sulphur in the acid phosphate. A 
comparison of acid phosphate with rock phosphate and gypsum, 
and with gypsum alone, and rock phosphate alone would give some 
valuable results. 
