96 



BULLETIN F. 



Concentration of nitrates by capillary sweeping. 



From this table it is seen that there had been a very strong 

 concentration of nitrates in the upper half of the soil column 

 and if the amounts recovered from the upper and lower sections 

 of the capillary cylinders are combined and compared with the 

 amounts recovered from the two sections of the check cylinders, 

 the results will appear as given in the next table : 



Differences in amounts of nitrates recovered by capillary concen- 

 tration and by ordinary washing. 



It thus appears that, under the influence of capillary sweep- 

 ing, it was possible to recover 24.22 per cent, more nitrates in 

 one series and 5.31 per cent, more in the other series. 



In another soil, a medium clay loam, under a bluegrass sod, 

 which had been reduced so low in its nitric acid content by the 

 action of the roots that only small amounts could be recovered 

 by washing the soil in the ordinary way, capillary sweeping, 

 by the method described, enabled solutions to be obtained which 

 yielded an increase of 17.57 per cent, in nitrates over the ordi- 

 nary method of washing, and of 23.83 per cent, in total salts as 

 indicated by the electrical method. 



