254 



Journal of Agricultural Research 



Vol. XEX, No. 6 



Table IX. — Relation between number of grams of sulphur oxidized and num,ber of 

 grams of potassium m,ade water-soluble 



In the New Jersey greensand composts, approximately 5X gm. of sul- 

 phur were oxidized for each gram of potassium made water soluble. 

 For the Maryland greensand composts, the ratio is approximately 8 to i. 

 The ratio varies with the materials used, the high-potassium greensand 

 having a lower ratio than the low-potassium greensand, and the com- 

 posts containing 20 per cent manure having a lower ratio than those con- 

 taining 10 per cent manure. For the composts in which soil was 

 substituted for all the manure the figures are not shown, but the ratio is 

 much wider, the amount of sulphur oxidized not being sufficient to make 

 water soluble any large amount of potassium. 



The results of this investigation would indicate that the composting 

 of greensand, or of soil rich in postassium, with sulphur and manure may 

 prove to be a practical and efficient method for obtaining available po- 

 tassium from comparatively insoluble materials. 



SUMMARY 



Two greensands, one containing 5.88 per cent of potassium and the 

 other 1.42 per cent, were used in studying the effect of sulphofication 

 upon the solubility of the potassium. The outstanding results of the 

 investigation are summarized in the following paragraphs. 



(i) In composts consisting of greensand, manure, and soil in different 

 proportions, an appreciable amount of the potassium of the greensand 

 was made water-soluble through sulphofication. 



(2) The composts containing the largest proportion of manure de- 

 veloped the highest degree of acidity, oxidized the greatest amount of 

 sulphur, and produced the largest quantity of water-soluble potassium. 



(3) The composts in which soil was substituted for a part of the manure 

 developed less acidity, oxidized less sulphur, and produced a smaller 

 amount of soluble potassium. 



(4) When all the manure was replaced by soil, the rate of sulphofication 

 was so slow that at the end of 23 weeks only a very small amount of 

 acidity had developed and very little potassium had been made soluble. 



