June IS, 1920 Effect of ManureSulpkur-Composts on Greensand 241 



ments, including the pots receiving 2 gm. of potassium chlorid. In their 

 conclusions they suggest — 



the possibility of utilizing the potash of greensand marl and the potash of natural soil 

 materials by growing soybeans and possibly certain other crops, which could be 

 returned to the soil and thus furnish available potash for those crops which can not 

 readily utilize potash from these natural sources. 



Lipman, McLean, and Lint (jo) composted loo-gm. portions of sea 

 sand, sassafras loam, and greenhouse soil with manure, sulphur, and 

 floats. At the end of 30 weeks analyses for water-soluble phosphoric 

 acid showed increases in all the mixtures to which both sulphur and 

 floats had been added. In one case 85 per cent of the total phosphorus 

 in the floats had been made available, the increase in available phos- 

 phorus paralleling the oxidation of the sulphur as measured in terms of 

 sulphates. In experiments conducted under field conditions, two of 

 these authors (9) have shown that the sulphur-floats-soil compost may 

 be utilized in making available the phosphorus of floats or raw ground 

 phosphate rock. They suggest that this compost could be employed to 

 advantage as a substitute for acid phosphate. Further studies at the 

 New Jersey Experiment Station by McLean (11) led to the conclusion 

 that the most economical combination for the production of available 

 phosphoric acid is a compost composed of 100 parts soil, 120 parts 

 sulphur, and 400 parts floats. 



Brown and Warner (5) found that by composting floats with manure 

 and sulphur it was possible to obtain a remarkable increase in the 

 amount of available phosphoric acid. The increase was greater where 

 the sulphur and floats were intimately mixed with the manure than 

 where the material was arranged in alternate layers. 



Experimenting with two Iowa soils, Brown and Gwinn (4) found that 

 while applications of manure alone increased the availability of raw 

 rock phosphate, the increase was much greater when sulphur was used 

 in connection with the manure. They bring out the fact that there is a 

 definite relationship existing between the sulphofying power of the soil 

 and the production of available phosphorus. 



Ames and Richmond (2) found that in an acid soil oxidation of 

 sulphur proceeded vigorously, approximately 50 per cent of the sulphur 

 being changed to the form of sulphate. In a basic soil the acidity 

 resulting from sulphofication was partly neutralized, so that the solvent 

 action on the rock phosphate was much less than occurred in the acid 

 medium. 



Since the inauguration of our work, Ames and Boltz (i) have pub- 

 lished additional data concerning the effect of sulphur on soils and 

 crops. These investigators found that both the nitrification of dried 

 blood and the oxidation of sulphur in soil mixtures resulted in the 

 liberation of potassium. They conclude that the liberation of the 

 potassium was brought about by the salts formed rather than by the 

 direct action of acidity on the insoluble potassium compounds. 



