252 



Journal of Agricultural Research 



Vol. XIX, No. 6 



comparatively large amounts of organic matter favor sulphofication and 

 the liberation of potassium under the conditions of this experiment. 

 These results are not in accord with those reported by McLean (//), 

 who, working with sulphur-floats-soil composts, came to the conclusion 

 that a compost is more efficient in the producing of available phosphorus 

 in the absence of large amounts of organic material. 



In Table VII the total potassium present in each compost, the water- 

 soluble potassium at the start, and the maximum water-soluble potassium 

 present at any one time during the period of 23 weeks are computed on 

 the basis of the initial weights of the composts. 



Table VII. — Total potassium made water-soluble (dry basis) 



Com- 

 post 



No. 



9 

 10 



13 



14 



Material added to i.soo gm. greensand. 



None 



Sulphtir 500 gm 



Sulphtir 500 gm. ; manure 500 gm 



Sulphur 500 gm.; mantu-e 250 gm.; soil 



250 gm 



Sulphur 500 gm. ; soil 500 gm 



Sulphiu- 500 gm.; soil 500 gm.; 0.02 per 



cent AU( 804)3 o-'^ HjO; 0.02 percent 



FeS04 o'.^ H2O 



Sulphur 500 gm.; soil 250 gm.; manure 



250 gm.; CaCOg 10 gm 



None 



Sulphur 500 gm 



Sulphiu- 500 gm.; manure 500 gm 



Sulphtu" 500 gm.; manure 250 gm.; soil 



250 gm 



Sulphur 500 gm. ; soil 500 gm 



Sulphiu- 500 gm.; soil 500 gm.; 0.02 per 



cent AU(S04)3 0.18 HgO; 0.02 per cent 



FeS04o"7 H2O 



Sulphur 500 gm.; soil 250 gm.; manure 



250 gm.; CaCOa 10 gm 



Total 

 number 

 grams 

 potas- 

 sium in 

 compost. 



83-38 

 83-38 

 85.68 



86.58 

 87.48 



87.48 



86.58 

 20. 97 

 20. 97 

 23.27 



24. 17 

 25.07 



25.07 

 24. 17 



Water- 

 soluble 

 potas- 

 sium at 



start 

 (percent- 

 age of 

 total). 



0.037 



•055 

 .832 



.408 



.094 



■494 

 . 112 



.243 

 3.22 



2.57 

 •29s 



•275 

 2-33 



Maximum water- 

 soluble potassium 

 present. 



O. 070 



•27s 

 15.28 



7.87 

 .812 



.812 



9.46 

 . 070 

 .251 



9. 62 



6.88 

 .389 



.310 

 6.49 



Percent- 

 age of 

 total. 



C. 084 



17-83 



9. 10 

 .928 



.928 



10.93 



•333 

 I. 20 



41-34 



28.50 

 I- 55 



1.24 

 26.85 



Reference to the last two columns of Table VII will show that, while 

 the actual amount of soluble potassium which formed in the composts 

 containing the Maryland greensand was much smaller than that which 

 formed in the composts containing the New Jersey greensand, the per- 

 centage of the total potassium made water-soluble in the former was 

 much greater than in the latter. One of the causes for this difference is 

 to be found in Table II, which shows the mechanical analyses of the two 

 greensands. The individual particles are much smaller in the Maryland 

 than in the New Jersey greensand, thus exposing a much greater surface 

 to the solvent action of the acids. Also, the glauconite particles of the 



