1922] WOODARD—SOIL FERTILITY loi 



phosphorus for loo or more years of alfalfa. No. 34 has phosphorus 

 enough to grow alfalfa 189 years, but sulphur enough for only 14 

 years. The phosphorus content of no. 28 is sufl&cient to grow 

 alfalfa for 131 years, but the same crop would deplete the sulphur 

 in II years. All these soils have sufficient phosphorus to grow 

 maximum yields of alfalfa for 20 years or longer, while all but two 

 would be depleted of sulphur in less than 20 years. 



Of the other crops mentioned, corn, wheat, and clover remove 

 smaller amounts of sulphur than phosphorus; while timothy, like 

 alfalfa, removes more sulphur than phosphorus. Timothy, how- 

 ever, removes only about one-fourth as much sulphur, and one- 

 fourth as much phosphorus as alfalfa, so that the supply of each 

 would last correspondingly longer, yet soil 9 A is the only one that 

 carries sufficient sulphur for 100 crops of timothy. Soil 9 A has 

 sulphur enough to grow timothy 159 years, clover 139 years, corn 

 232 years, and wheat 355 years. No. 34 has phosphorus enough 

 for 401 com crops, 568 wheat crops, and 341 clover crops; yet the 

 sulphur would be depleted by 80 corn crops, 122 wheat crops, or 

 48 clover, crops. The lowest phosphorus content is in soil i A, a 

 sandy loam soil, which has 720 pounds of phosphorus in the surface 

 7 inches of soil. The phosphorus in this soil would be depleted 

 by growing corn 42 years, wheat 60 years, timothy 80 years, clover 

 36 years, or alfalfa 20 years. In the same soil the sulphur would 

 be removed by 40 years of corn, 62 of wheat, 28 of timothy, 24 of 

 clover, or 7 of alfalfa. 



Table III shows the importance of both sulphur and phosphorus 

 if maximum crops of legumes, particularly alfalfa, are to be grown. 

 It also shows that, in most soils, sulphur is more likely to be defi- 

 cient than phosphorus. It does not take into account the leaching 

 of these elements from the soil, which is practically nil in the case 

 of phosphorus and very high in the case of sulphur; nor the supply 

 in the rain water, which is nil in the case of phosphorus and may be 

 quite high in the case of sulphur near cities in the humid regions. 

 Whether the amount of sulphur lost in the drainage water exceeds 

 that gained in the rain water is still unknown. It is certain that 

 the amount of leaching will vary with the character of the soil, the 

 rainfall, and the character of the plant growth. The amount of 



