338 



Journal of Agricultural Research voi.xvin,No.6 



of soil were present. The soil extract was prepared by shaking 200 

 gm. of soil with 2 liters of distilled water and filtering through paper. 



Six sets of composts, No. 11 to 16, were started December 22, 1917. 

 One-half of each set was prepared without sulphur and one-half with 

 sulphur, as shown in Table XI. 



Table; XI. — Composition of composts 11 to 16 {in grams) 



Ingredients. 



Rock phosphate . 



Sulphur 



Starter 



Total. 



without 

 sulphur. 



204 



With 

 sulphur. 



5° 

 4 



204 



The first three sets were maintained at 20 per cent moisture content — 

 No. II with distilled water, No. 12 with tap water, and No. 13 with 

 soil extract. The last three sets were maintained at 20 per cent mois- 

 ture content with tap water. Two gm. of Station farm soil (the same 

 kind of soil used in composts i to 10) were added to compost No. 14, 

 10 gm. to No. 15, and 20 gm. to No. 16. All were stirred every 7 to 10 

 days. The ammonium-citrate-soluble phosphorus was determined on 

 July 22, 191 8, after a period of about 30 weeks. The results are given 

 in Table XII. 



Table XII. — Percentage of ammonium-citrate-soluble phosphorus in -water-free com- 

 posts II to 16, showing gain resulting from presence of sulphur 



SULPHOFICATION IN DIFFERENT TYPES OF SOILS 



The following experiments were carried on for the purpose of deter- 

 mining the sulphof ying powers of different types of soils which were 

 later used in compost experiments. The soils represent the principal 

 types, other than the Trenton, found in Kentucky. 



Two loo-gm. portions of air-dry soil were intimately mixed with 0.025 

 and 0.050 gm. of sulphur, respectively. Sixteen gm. of each were then 

 taken, 100 cc. distilled water was added, and the whole was shaken 

 constantly for 7 hours. The remainder was maintained at 20 per cent 

 moisture content with distilled water and stirred every 7 days. At 



