114 AGRICULTURE 



superior effect of the former manure are 

 probably rather complex. Nitrate of soda 

 sinks more easily and to a greater distance 

 into the soil, and the roots of the mangold 

 crop, following the nitrate, occupy a much 

 more extended range of feeding ground, and 

 so are brought into contact with supplies of 

 potash naturally present in the soil which they 

 can utilize. While it cannot be maintained 

 that soda can replace potash in the economy 

 of the plant, it is possible that certain physio- 

 logical processes may take place by the aid 

 of soda where potash is not available, and 

 thus the soda of the nitrate of soda confers 

 a benefit upon the crop which is excluded in 

 the case of the sulphate of ammonia. That 

 there are good grounds for this suggestion 

 appears to be proved by the fact that where- 

 as the mangold crop at Rothamsted responds 

 in a very striking manner to the use of 

 potash in the presence of ammoniacal dress- 

 ings, there is no such marked response where 

 potash is employed in the presence of dress- 

 ings of nitrate of soda. The conclusion 

 would therefore appear to be justified, that 

 in the latter case potash is not so much 

 required, because, as has been indicated, 

 the soda has to a certain extent acted as a 

 substitute. 



