Dec. 15,1919 Oxidation of Sulphur in Soils 341 



Another interesting fact is that about the same percentages of the 

 total phosphorus present was in water-soluble form in No. 3 and 4; and 

 the same held true for the citrate-soluble form, notwithstanding there 

 was over 400 per cent more phosphorus present in No. 4. The amount 

 found soluble in water, however, was much less than in ammonium cit- 

 rate in all cases. One reason why larger amounts of soluble phosphorus 

 were not obtained was probably the absorptive capacity of the soil for 

 compounds of this element, which prevented the portion thus occluded 

 from being estimated, although it existed in a soluble form. 



It will be observed further that about 13 per cent of the phosphate 

 naturally present in this soil has been converted into a water-soluble 

 form and 80 per cent into citrate-soluble form. Composting without 

 sulphur has also shown some benefit, since 14 per cent of the phosphorus 

 in No. I and 6 per cent in No. 2 was citrate-soluble, although the latter 

 contained over 500 per cent more total phosphorus than No. i. The 

 apparently inconsistent amounts of total phosphorus shown in the earlier 

 compost experiments are explained by the fact that a large amount of 

 soil was used in preparing these experiments, and since the quantity of 

 phosphate was large and not evenly distributed, probably a uniform 

 mixture was not obtained. Subsequent mixings of the separate piles, 

 however, during the experiments and before the totals were determined 

 make the analyses for this element trustworthy. 



It will further be observed in Table V that nitrification took place in 

 all piles regardless of the amount of acid formed. There was an irregular 

 but gradual increase in nitrates until December 12, 191 7, at which time 

 the maximum amounts were found in all cases. These maximums were 

 approximately 17 per cent of the original total nitrogen present in each 

 except No. 4, in which there was 20 per cent. The actual amounts of 

 nitrogen nitrified at this time were 232 mgm. in No. i, 182 mgm. in No. 

 2, 213 mgm. in No. 3, and 208 mgm. in No. 4. This is of interest when 

 Table II shows that No. 3 contained 60 times more acid at this time. It 

 should be borne in mind that just previous to this the starter had been 

 added and this was the first time that any pronounced activity of the 

 sulphofying cganism was apparent, as indicated in the phosphate 

 solubility in Table III. 



As the acidity developed there was a distinct loss of nitrate in only one 

 sample. No. 4, which in August, 1918, showed a decrease but still con- 

 tained 300 per cent more than at the beginning, while the acidity had 

 increased 40,000 per cent. 



The results on total nitrogen are not conclusive in regard to the be- 

 havior of this element during the experiments. One set of analyses in 

 Table V indicates there had been a gain. The loss in weight due to the 

 decomposition of the manure does not account for this gain. Neither 

 does the nitrogen contained in the amount of tap water added explain it. 



