18 



THE MANURE HEAP 



[CH. 



The artificials supplied to the mangolds were f cwt sulphate 

 of ammonia, 1 J cwts nitrate of soda, 6 cwts superphosphate, 1 J cwts 

 sulphate of potash. Nothing was added to the other crops. 



Again, in a rotation experiment made by the Leeds University 

 Agricultural Department 20 tons of dung supplemented by 

 artificials gave larger returns than 38 tons of dung without 

 artificials. 



Potatoes often respond to a complete dressing of artificials in 

 addition to dung. Thus, the following results were obtained in 

 the Irish experiments carried out over the 11 years 1901-11 at 

 353 centres 1 : 



No manure 



15 tons farmyard manure per acre 



20 tons farmyard manure per acre 



15 tons farmyard manure per acre + 1 cwt sulphate of ammonia ... 



15 tons farmyard manure per acre + 1 cwt sulphate of ammonia 



+ 4 cwts superphosphate ... 

 15 tons farmyard manure per acre + 1 cwt sulphate of ammonia 



+ 4 cwts superphosphate + 1 cwt muriate of potash ... 



tons cwts 

 4 



8 4 



9 2 

 9 3 



9 



10 



19 

 17 



1 cwt of sulphate of ammonia is thus seen to be as effective 

 as 5 tons of dung, while the addition of 4 cwts of superphosphate 

 still further increased the yield, and 1 cwt of muriate of potash 

 gave yet another 18 cwts of potatoes. 



In other cases the increase in crops may be less, but there 

 is an improvement in quality, always an important matter for 

 potatoes: thus in the Yorkshire experiments 2 10 tons of dung 

 gave an increase of 2| tons in crop, but a second 10 tons only 

 gave a further 16 cwts: 



Large v. small dressings of dung. 



1 J&urn. Dept. Agric., Ireland, 1913, 13, 264-276. 



2 Leeds Bull No. 58. Report on the manuring of potatoes, 1899-1903 and 1904-5. 



