38 THE POTATO. 



potato manure. It is, however, universally agreed that 

 potash manures should not be used indiscriminately for 

 the purpose. Clay soils, for instance, usually contain suffi- 

 cient potash to meet the requirements of the potato. On 

 such a soil it would be well to experiment with its use, 

 and ascertain if it be wise economy to apply it to any 

 extent. We advise this course because, although a clay 

 soil may contain potash, the latter is not always available 

 for the crop. On light, chalky, and peaty soils, potash 

 is indispensable. Three forms of potash are available 

 kainit, muriate (chloride), and sulphate of potash. The 

 former is the cheapest form of potash, and, as it contains 

 a small proportion of magnesium salts, it supplies what 

 little may be required of the latter. It is, however, slow 

 in action, and requires to be applied either in winter or in 

 early spring to be of the greatest value to the crop. Muri- 

 ate or chloride of potash is often advised as a good potato 

 manure. It is richer in potash than kainit, one ton being 

 equal to four of the latter, and the price is correspondingly 

 higher. Sulphate of potash is also richer in potash than 

 kainit, and dearer. The muriate is similar in action to 

 kainit, but, owing to its liability to form calcium chloride 

 in the soil, a substance harmful to plant life, it is not alto- 

 gether a safe form of potash to use. Then again, it is said 

 to have a tendency to cause waxiness in the tubers. Sul- 

 phate of potash, on the other hand, is a perfectly safe form 

 of potash, and, unlike kainit, it may be applied at the time 

 of planting. 



Sulphate of Iron Dr. A. B. Griffiths is the autho- 

 rity who so firmly believes in, and so strenuously advo- 

 cates, the use of sulphate of iron as an ingredient in potato 

 manure formulas. In his " Treatise on Manures " (Whit- 

 aker and Co.), he plainly demonstrates its value, not only 

 as an aid to obtaining a greater yield of tubers, but also as 

 a preventative of the potato disease. According to his 

 statements, an application of iron sulphate will give a 

 greater yield than one of kainit. He asserts, moreover, 



