44 TRUCK-FARMING AT THE SOUTH. 



other vegetable exhaustive of potash, an application of a 

 salt of potash either alone, or of a fertilizer largely con- 

 taining it, becomes indispensable. All potash salts, be- 

 ing exceedingly soluble, are liable to be leached out of 

 sandy land. A crop of one hundred and fifty bushels of 

 Irish potatoes will remove from the soil, in the tubers, 51.3 

 Ibs. of potash, 1.44 Ibs. of phosphoric acid, and 30. 6 Ibs. of 

 nitrogen. Formerly the ashes of hard-woods was nearly 

 the only, and limited source of potash; but recently the 

 kainit mines in North Germany, near Stassfurt and Leo- 

 poldshall, provide this element in enormous quantities. 

 The lower grades contain a constituent, the chloride of 

 magnesium, which is actually injurious to plant growth. 

 Years ago, like J. H. H. Gregory of Marblehead, Mass., I 

 had an experience which showed the detrimental effects 

 of this salt in the ruin of a potato crop. Mr. Gregory 

 mixed a compost of twenty-eight bbls. of hen manure, 

 twenty-eight bbls. of dry, rich soil, twelve bbls. of fine 

 ground bone with three bbls. of kainit. This was allowed 

 to heat twice before it was applied, at the rate of two quarts 

 to the hill, and according to his custom, cabbage seed 

 was sown in the field, on each hill. The seed sprouted; 

 but the little seedlings were killed as soon as the first 

 rootlets reached the fertilizer. As large quantities of this 

 kainit are being introduced into the South, statements by 

 Prof. Atwater (American Agriculturist, Vol. XXXVI, 

 No. 11) are here given as a warning against the improper 

 or. indiscriminate use of the lower grades of these potash 

 salts: "The mines at Stassfurt, Leopoldshall and Wes- 

 teregeln are from six hundred to one thousand two hun- 

 dred feet deep, and the area of deposit is calculated at 

 six hundred square miles. The salts, as taken from the 

 mines, contain only a small proportion of potassium com- 

 pounds, the bulk consisting of materials which have com- 

 paratively little agricultural value, and are sometimes 

 positively injurious. They are, therefore, subjected to 



