108 



Mean distribution of nitrates, sulphates and chlorides, in six soil 

 types under mulched and unmulched surfaces. 



From this table it is seen that the more rapid capillary 

 movement upward under the unmulehed surfaces had so counter- 

 acted diffusion downward as to leave all of these salts much more 

 concentrated under the unmulched surfaces. Comparing the 

 data in the table it will be seen that the 3 to inch level con- 

 tains more than 3 times as much nitrates and more than twice 

 as much sulphates under the mulched surfaces, and similar re- 

 lations hold down to and including the 12- to 15-inch level. 



In the case of chlorine, whose rate of diffusion is higher, 

 there is less difference, but the tendency here is clearly marked. 



It has been shown in preceding pages that the three important 

 bases, are rapidly carried upward also by capillarity, and it is to 

 be expected that had these been determined in this series, some- 

 what similar relations would have been found. 



INFLUENCE OF 3-INCH EARTH MULCHES ON THE DISTRIBUTION 

 OF PHOSPHATES, SILICA AND BICARBONATES. 



In the next table there are brought together the mean values 

 showing the relative distribution of phosphates, silica and bicar- 

 bonates under the two conditions of surface. 



