POTASH MANURES 155 



duces the root system to develop corre- 

 spondingly, in order that the plants may 

 secure the nitrogen which though not with- 

 out an effort, as it were is obtainable. 

 Other things being equal, plants with an 

 extensive root system are likely to obtain 

 larger quantities of such substances as potash, 

 naturally present in the soil, than plants 

 with more restricted roots. But it is also 

 believed that the soda of the nitrate of soda 

 can to a certain extent replace potash in 

 the nutrition of plants perhaps more so in 

 case of some plants, e.g. mangolds, than of 

 others. It is not suggested that potash is 

 an unessential element of plant food in the 

 case of mangolds, but it is probable that 

 abundance of soda, whose properties in 

 many respects agree with those of potash, 

 makes it unnecessary that such a crop 

 should have access to such large quantities 

 of potash as would otherwise be required. 

 As has already been pointed out, also, it is 

 probable that nitrate of soda can liberate a 

 considerable amount of potash in the soil, 

 which thus becomes available for the use of 

 plants. 



Where leguminous crops are grown upon 

 medium and lighter soils, they often respond 

 markedly when additions of potash are 



