3H The Tnjluetice of FotKherds on Nitrification 



percolates drained into the collecting bottles. The necessary repairs 

 were made as speedily as possible; but still there were many breaks in 

 the percolation record. Later on, the glass tubes were replaced by metal 

 tubes, paraffined inside. 



Fortunately, the set of jars Nos. 9 to 12 escaped the accidents referred 

 to above. Complete analytical records for the percolates from these jars 

 are noted below. 



Table III. 

 Percolates from the Jars No!<. 9 — 12. 



During the whole period the following amounts of nitrogen (as 

 nitrates) were washed out: 



These results show that potsherds have produced increased nitrifica- 

 tion and that thirty per cent, potsherds are specially efficient, the amount 

 of nitrate from the jar filled with this being more than twice the amount 

 washed out from the soil containing no added potsherds. Apparently, 

 the presence of potsherds renders the soil more open and favours gaseous 

 interchange between the soil and the atmosphere. More oxygen is thus 

 available for the nitrification of the organic matter. 



The amount of dissolved oxygen was practically the same in all these 

 later percolates, and so, its determination was stopped. 



Both the observations as to the marked influence of the presence of 

 thirty per cent, potsherds and as to the constancy of the amount of 

 dissolved oxygen in the later percolates were also found to hold good in 

 the cases of the drainage waters obtained from the other jars (Nos. 1 to 8). 



