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A MANURE. 47 



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h-needed fertilizer soda. The chief source of 

 supply is from salt-mines, such as exist so largely in 

 Cheshire, and also from the evaporation of sea-water. 

 Good samples of Cheshire salt contain as much as 

 98 per cent, of chloride of sodium; but the salt 

 obtained from sea-water usually contains chloride of 

 magnesium, and it is more than usually disposed to 

 become moist, which renders its distribution more 

 difficult. Its action as a fertilizer is in many respects 

 peculiar, by reason of its apparently inconsistent influ- 

 ences, for in many cases we see it giving a decided 

 check to vegetable growth, and yet thereby increasing 

 the production of corn. For some crops, such as the 

 mangel wurzel, salt is a direct requirement of the 

 plant as food. Beans, cabbages, and onions also 

 appear to flourish with liberal supplies. The analysis 

 of the ash of mangel wurzel shows considerable varia- 

 tion in the quantity of salt present. According to 

 Way and Ogston the average of four analyses of the 

 bulb showed a variation of from 10 per cent, to 49*51 

 per cent, of salt in the ash, and an average of 24*55 

 per cent. The tops of the mangel wurzel, on the 

 same authority, contained 33*96 per cent, of salt in 

 the ash. It is therefore evident that this crop in 

 particular requires a supply of salt as plant-food. It 

 is present in the ash of every cultivated plant, and it 

 must therefore be regarded as generally desirable as 

 a food for these crops. The necessity for supplying it 

 to the land will be determined in a great measure by 

 the supply already existing in the soil. Lands which 

 are situated near the sea have a supply carried by 

 winds from the sea, and the quantity of salt which is 

 thus carried inland for twenty, thirty, or sometimes 

 even forty miles, will surprise those who have never 

 tested this supply. 



90. One important influence which salt exerts on 

 vegetation arises from its power to check plant 

 growth, possibly arising from the action of the 



