658 POTATO ROT. 



than they could derive from run-out seed, in wet soil, or in 

 contact with rank manure. 



6. Planting in new soil and the use of mineral manures. 

 It is generally observed that the potato has been most healthy 

 when planted in new, virgin soil, before the unskilful agricul- 

 turist has extracted from it the stores of alkaline and other 

 mineral manures remaining in it from the ashes of the forest. 

 The composition of the ash of the potato at once explains the 

 reason of this, as the following table, talien from Johnson, will 

 show : — 



Ashes in 10,000 lbs. of the roots and stems of the potato. 



Potash, - . - - 



Soda, _ _ - _ 



Lime, - _ _ . 



Magnesia, _ _ _ 



Alumina, - - - - 



Ox. iron, _ - - - 



Silica, - - - - 



Suphuric acid, - - - 



Phosphoric do. - - - 



Chlorine, - - - - 



82.83 308.4 



Here we have very large proportions of lime and potash : 

 the latter forming nearly 50 per cent, of the ashes of the roots. 

 Now these substances, potash especially, are plentifully sup- 

 plied to the soil by the ashes of the woods, and arc usually de- 

 ficient in exhausted lands. Hence, if we apply to run-out, or 

 long cultivated soil, lime, wood-ashes, gypsum, (sulphate of 

 lime,) common salt, (chloride of sodium,) bone dust, (phos- 

 phate of lime,) we supply it with some or all of the more im- 

 portant substances in the above table, and thus assimilate it to 

 the virgin soil in which experience proves the potato to thrive 

 best. 1 have found, by experience, that healthy potatoes 

 (though not a large crop) could be obtained by planting with 



