340 



Journal of Agricultural Research voi.xviii,no.6 



EXPERIMENTS WITH COMPOSTS OF DIFFERENT TYPES OF SOILS 



The same rock phosphate and sulphur were used as in the former ex- 

 periments. The sulphof ying soil was from a new lot obtained from the 

 same place as the other. The composts were prepared on March 15, 

 1 91 7, as follows: 



Table XIV. — Composition of composts {in grams) prepared with various Kentucky soils 



Ingredients. 



Without 

 sulphur. 



With 

 sulphur. 



Soil 



Rock phosphate. 



Sulphur 



Starter 



200 



6?i 



Total. 



340 



66% 

 200 



66^ 

 6K 



340 



The same soils were used here as in the sulphofication experiments, 

 and the soil used in the former experiments was also included. The 

 mixtures were kept at 20 per cent moisture content with distilled water 

 in Mason jars covered with watch glasses. They were stirred every 7 to 

 10 days until September 27, 191 8, and after this date they were not stirred 

 but kept moistened. The results are shown in Table XV. 



Table XV. — Percentage of ammonium-citrate-soluble phos phones in water-free composts 

 prepared with various Kentucky soils 



County. 



Soil and rock phos- 

 phate. 



Sept. 27, 

 1918. 



Mar. 7, 

 1919. 



Soil, rock phosphate, 

 and sulphur. 



Sept. 27, 

 191S. 



Mar. 7 

 1919. 



Lawrence . . 

 Warren 



Mason 



Muhlenberg 



Barren 



McCracken. 

 Madison. .. . 

 Jefferson. .. . 

 Fayette. . . . 



o. 124 

 . 141 



• 132 

 . 169 



■^3S 

 •135 



• 130 

 . 162 

 .178 



103 

 117 

 122 



139 

 126 

 107 



125 

 136 



17s 



456 

 469 

 411 

 480 

 436 

 452 

 517 

 493 

 604 



0-473 

 .488 



•523 

 •531 

 .470 

 .501 



•549 

 .501 

 .611 



DISCUSSION OF RESULTS 



It will be observed in Table III of the earlier experiments that 4 per 

 cent of the phosphorus present in No. 4 was citrate-soluble after 7 months, 

 60 per cent after 15 months, and 83 per cent after 24 months. The 

 amount in soluble form after 7 months, however, is much less than Dr. 

 Ivipman found in his experiments. In fact, in the present experiments 

 no pronounced action developed until the starter was added. 



