40 THE POTATO. 



that in the experiments made with kainit and iron sul- 

 phate, in the plot dressed with the former the crop was 

 diseased, while that grown in the plot dressed with the 

 latter was quite free from disease. We must certainly say, 

 as the result of our own and others' experiments with the 

 use of iron sulphate on crops and plants, that there is 

 some justification for Dr. Griffiths' claim as to its manurial 

 value. 



Nitrogenous Manures. Apart from farmvjml 

 manure, sulphate of ammonia and nitrate of soda are the 

 chief nitrogenous manures required for the potato crop. 

 Of the two, nitrate of soda is the one generally used. In 

 any case, this is best in dry seasons and on dry soils. Sul- 

 phate of ammonia is more suitable for damp soils and 

 wet seasons. It is said that when farmyard manure lias 

 been liberally used, sulphate of ammonia has the effect of 

 causing the plants to make smaller tubers. On the whole, 

 it is deemed best to apply the latter only on damp soils in 

 wet seasons, or where farmyard manure has been used. 

 Neither nitrate of soda nor sulphate of ammonia must be 

 used too freely, as they promote a too luxuriant growth, 

 and predispose the plants to disease. Soot and malt dust 

 are excellent nitrogenous manures for potato culture, espe- 

 cially for early crops. Both should be applied along the 

 drills just before planting. From eight to ten cwt. of malt 

 dust, of fifty to eighty bushels of soot per acre, will be 

 a suitable dressing. 



Guano. The various forms of Peruvian guano, such as 

 those rich in phosphates, may be used at planting time, 

 while those richer in nitrogen are valuable for top-dressing. 

 Fish guano acts more slowly, but is useful at planting 

 time. 



Formulae for Field and Garden Crops. So 



much for a description of the various ingredients generally 

 used in the composition of potato manures, and now we 



