90 IMPROVEMENT OF THE SOIL 



land-shells, immense beds of which are found along our 

 southern Atlantic border, and frequently in the interior, 

 where fresh-water ponds have apparently existed, and 

 where the marl is generally covered with a bed of peat 

 earth. This may be applied at the rate of 25 to 30 loads 

 to the acre ; and may be spread upon stubble, upon a fal- 

 low, or upon grass. While it benefits the herbage, the 

 mineral sinks into the soil, and prepares it, when broken 

 up, for the arable crop. Its effects are slower than those 

 of lime, though they are said to last longer. 



A species oi green sand is coming into extensive use 

 in the maritime borders of New Jersey, Maryland, and 

 Virginia, which is found of great potency in imparting 

 fertility to the soil. Its fertilizing properties do not con- 

 sist of carbonate of lime, but of potash, of which it gives 

 on analysis about 14 per cent. It is applied like marl, 

 but in somewhat less doses. 



Common salt has been highly recommended as a fer- 

 tilizing material, and in many cases certainly has been 

 used with great effect ; yet there do not seem to be 

 any established rules to guide in its appHcation. It is no 

 doubt beneficially applied to some soils, and to some 

 crops, while upon other soils and other crops it seems 

 to be inoperative. It should be used sparingly, and 

 should be mixed with manures or composts. 



It has been ascertained by experiments made by Hitt, 

 Knight, Johnson, and others, that salt is serviceable in 

 preventing some diseases of plants, as well as of animals. 

 In the late investigations by a committee of the British 

 Parliament, on the question of reducing the duty on salt 

 for agricultural purposes, it abundantly appeared, that its 

 free use to farm-stock was the best preventive of disease ; 

 and that in several instances, where flocks of sheep had 

 been diseased, they had been restored to health by the 

 liberal use of this condiment. Used in moderate quan- 

 tities, it is said to prevent mildew on the gooseberry, and 

 on various garden and field crops. 



Until we know more of the peculiar properties of soils, 

 and of the operation of mineral mixtures, the only way to 

 determine the efficacy and economy of these applica- 



