SODIUM CHLORIDE (COMMON SALT). 105 



development of the plant. But all plants and all seeds do not stand 

 the action of salt to the same extent. As a result of some laboratory 

 experiments, it is recognized that barley stands stronger doses of salt 

 than tares, and oleaginous seeds resist salt better than other seeds. 



Role of Common Salt as Manure. — To a greater extent than 

 potassium the sodium necessary to the plant exists in all soils in 

 sufficient quantity. Practice has, however, shown that the application 

 of common salt to a soil rich in sodium is always followed by good 

 results, provided always that a certain dose is not exceeded. In these 

 conditions it is evident that it cannot act as (plant) food, and its role 

 must be regarded fi'om another point of view, and possibly the follow- 

 ing. According to Braconnot, one of the first effects of salt added 

 to a soil is to keep it moist. This property, which the salt owes 

 to its affinity for water, is in a high degree favourable to the transport 

 of the elements assimilated in the plant. Liebig, Voelcker, Malaguti, 

 and Peligot agree in attributing to common salt the role of a solvent 

 of phosphate of lime. Liebig in fact found that a solution of 1 kilo- 

 gramme (2-2 lb.) of common salt in 500 litres (110 gallons) of 

 water dissolves 15 grammes, say ^ oz., of phosphate of lime. 

 According to Boussingault, common salt decomposes carbonate of 

 lime into calcium chloride and carbonate of soda (this action has 

 been disputed by Kuhlmann, Isidore Pierre, and Peligot) ; the latter 

 product would be absorbed by the plant, or would act in the soil on 

 the organic matter to hasten its oxidation and contribute to the forma- 

 tion of nitrate of soda. The good effects of salt may be confirmed by 

 spreading a small quantity on the land. In big doses it is, on the 

 contrary, antiseptic and prevents the putrefaction of organic matter in 

 the soil, and consequently the formation of nitrates. The nitrification 

 of organic matter goes on slowly in cold weather ; salt, therefore, has 

 more action in southern countries than in northern countries 

 (Kuhlmann). For the action of salt on arable land to be complete 

 heat and moisture must be intermittent. In two dry years like 1846 

 and 1865 salt may be injurious because it then acts as a caustic, and 

 corrodes the plant (Fraisse). Plants on the sea-coast are watered 

 naturally by the salt water of the sea. There, where the desiccating 

 action of the wind cannot wither up the plants behind the walls, the 

 hedges, or the ramparts formed by forests, vegetation becomes 

 luxuriant. It is otherwise quite on the seashore, the excess of salt, 

 especially magnesium chloride, being as injurious to plants as the 

 drying wind. Barren zones are thus to be found along 'the shore, 

 according to whether the wind blows more or less frequently from the 

 sea and according to the dryness of the year. The remarkable fertility 

 of the " polders " of Holland is attributed to the temporary submersion 

 of certain land a hundred years ago. In Camargue the soil is highly 

 fertile, but the young blades of cereals must be protected by a layer 

 of I'eeds, so as to prevent too great drying. The experiments of Lecocq 

 have shown that it requires 150-200 kilogrammes (330-440 lb.) of 

 common salt per hectare, say 132-176 lb. per acre, as a manure for 

 lucerne, 250-300 kilogrammes (550-660 lb., say 220-264 lb. per acre) 

 for flax and wheat, and 264 lb. per acre for barley. Kuhlmann, 



