RELATION OF SULPHUR COMPOUNDS TO PLANT 

 NUTRITION 



By E. B. Hart, Chemist, and W. E. Tottingham, Assistant Chemist, Department of 

 Agricultural Chemistry, University of Wisconsin 



INTRODUCTION 



The four elements, nitrogen, phosphorus, potassium, and calcium, still 

 play the most important role in soil treatment. For a number of years, 

 however, other materials which stimulate growth in vegetation have been 

 studied by chemists and agronomists. 



The so-called catalytic fertilizers, such as the salts of manganese, have 

 often been shown to increase plant growth. In addition, studies have 

 been made of radium, hthium, sodium, arsenic, barium, copper, and some 

 other elements. While these may stimulate plant growth, their appli- 

 cation is not at present regarded as of economic importance. These ele- 

 ments are either not at all necessary for the plant's cycle of growth or, 

 so far as we know, are abundantly supplied in all ordinary soils. 



In the case of sulphur the relation appears to be somewhat different. 

 It was pointed out in 191 1 by Hart and Peterson (5)^ that the total sul- 

 phur content of the soils examined was low, being approximately equal 

 to the phosphorus content. This work has been confirmed by Shedd (12) 

 for Kentucky soils and by Robinson (11) for the important soil types of 

 the United States. It was further shown by Hart and Peterson (5) that 

 the sulphur content of our common farm crops was considerable, cereal 

 grains containing about half as much sulphur as phosphorus and legume 

 hays sometimes more sulphur than phosphorus, while the Cruciferae, 

 such as cabbage, turnips, etc., may contain two to three times as much 

 sulphur as phosphorus. 



It has been urged by Hopkins (6) that the high sulphur content of 

 plants does not represent their needs, but merely shows the superabun- 

 dance of sulphates in the soil water, with an extraordinary consumption 

 by the plant. This may apply to the stem and roots of plants, but not 

 to the seed. The seeds maintain a fairly constant composition and, as 

 shown by Peterson (9), either contain but traces of sulphates, or more 

 probably none at all. The criticism, then, that a high sulphur content 

 of a plant merely represents a large soil supply can not possibly hold for 

 seeds. It is true that the sulphate sulphur and probably other forms of 

 sulphur in the stems and roots of plants will vary with the soil supply. 

 In these plant parts sulphates may be present where the soil supply is 

 plentiful. The same statement, however, is equally true of phosphates. 



' Reference is made by number to " Literature cited," p. 249. 



Journal of Agricultural Research, Vol. V, No. 6 



Dept. of Agriculture, Washington, D. C. Nov. 8, 1915 



aq Wis.— I 



(233) 

 9839°— 15 2 



