1922] WOODARD—SOIL FERTILITY . 105 



3. The sulphur contents in the surface soil vary from 0.0118 to 

 0.0905 per cent, while the phosphorus contents vary from 0.0360 

 to 0.3407 per cent. All the upland soils and most of the alluvial 

 soils are low in sulphur. Most of the Kentucky soils and one of 

 the Indiana soils are high in phosphorus. This is undoubtedly due 

 to the influence of the rock from which the soils were formed, as all 

 the Kentucky samples were from soils derived either from the Tren- 

 ton limestone or the Cincinnati limestone, both of which are high 

 in phosphorus content. 



4. The sulphur and phosphorus contents were calculated to 

 pounds per acre in the surface soil, and compared with the amounts 

 of sulphur and phosphorus removed by maximum crops of corn, 

 wheat, timothy, clover, and alfalfa. The highest sulphur content 

 is sufficient for only 39 years of alfalfa, 139 of clover, 159 of timothy, 

 355 of wheat, or 232 of corn; while the lowest sulphur content is 

 suflScient for only 5 years of alfalfa, 18 of clover, 21 of timothy, 46 

 of wheat, or 30 of com. The lowest phosphorus content is equal 

 to the amount removed by 42 years of corn, 60 of wheat, 80 of 

 timothy, 36 of clover, or 20 of alfalfa. On the other hand, it would 

 take 401 years of com, 568 of wheat, 757 of timothy, 341 of clover, 

 or 189 of alfalfa to remove as much phosphorus as is found in the 

 soil with the highest phosphorus content. 



5. On some of the soils tobacco, clover, and alfalfa have been 

 benefited by the use of gypsum. The results, however, are not 

 quantitative. More field experiments are needed and greater care 

 should be taken to eliminate other factors as far as possible. Each 

 treatment should be repHcated to reduce the probable error. 



This investigation was conducted under a research fellowship 

 from the Gypsum Industries Association. The work was performed 

 at the University of Chicago in the Hull Botanical Laboratory under 

 the direction of Dr. William Crocker. The author wishes to 

 thank the Gypsum Industries Association for their kindness in 

 fumishing the fellowship and Dr. Crocker for his kind and helpful 

 advice and criticism. Thanks are also due Dr. Frederick Koch 

 for his kind advice and criticism of analytical methods. 



University of Illinois 

 Urbana, III. 



