1922] WOODARD—SOIL FERTILITY 103 



the second clover crop, and Mr. Tuomey an increase in alfalfa. 

 Neither of these men weighed the hay, so the results are not quan- 

 titative. Mr. Sharp'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 Uke 

 tobacco. Mr. Fowler'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 abimdance 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 hmiting 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. As a 

 general rule soils are deficient in phosphorus, and fanners 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. 



