290 SOILS AND MANURES 



other hand, it may be due to some indirect action of the 

 salt as a whole. 



Common salt possesses a certain power of flocculating 

 clay, but it is not so efficacious as lime. It is slightly 

 deliquescent, and the small amount of moisture it attracts 

 may possibly be of some benefit to the plants. It has 

 been supposed that it renders plant foods in the soil more 

 readily available, but this is not supported by any 

 satisfactory experimental evidence. By reaction with 

 lime it tends to decalcify the soil, and it is said to favour 

 "pan " formation. 



The use of common salt has also been recommended 

 on the ground that it has an antiseptic action and pre- 

 serves the manure (farmyard manure). If it does retard 

 the action of manure, it should certainly not be used 

 unless the soil is too rich, i.e., contains too much 

 nitrogen. It retards the growth of the plants ; thus straw 

 is rendered less luxuriant and less liable to be laid, and 

 the intense (rank) green colour produced in grass and 

 root crops by an overdose of nitrate of soda may be 

 corrected. If the soil has become overstocked or over- 

 dosed with nitrogenous matter, such a condition can 

 sometimes be corrected by using additional quantities 

 of phosphates and potash manure ; this enables the 

 plant to utilise the excess of nitrogen, and increased pro- 

 duction results instead of rankness. Common salt, ap- 

 parently, either prevents the plants from absorbing the 

 excess of nitrogen or of using it advantageously. The 

 principal benefits can therefore be obtained by using less 

 manure. 



Salt is sometimes spread on pastures to induce the 

 stock, which are very fond of the taste of it, to eat down 

 the herbage more closely. Any improvement produced 

 in this way cannot properly be regarded as a manurial 

 effect. 



