320 SYSTEMS OF MANURING CROPS [chap. 



In both these cases about 30 loads of farmyard 

 manure are put on the stubble and ploughed in the 

 autumn before the potatoes are grown, artificial 

 fertilisers to the value of 20s. or 30s. are also added in 

 the spring. 



Another rotation in the Dunbar country, so famous 

 for the high quality of its potatoes, avoids the use of 

 any farmyard manure : — 



Swedes, in part fed on the land. 



Barley. 



Clover, cut for hay. 



Clover, grazed with cake and corn. 



Potatoes, no farmyard manure. 



Oats. 



On the Lincolnshire fen soils a common rotation is 

 as follows : — 



Swedes ^, Potatoes J, with farmyard manure. 



Wheat. 



Seeds. 



Wheat. 



Oats. 



On the black soils of Lancashire a common rotation 

 is : — 



Oats. 

 Potatoes. 

 Oats. 



Seeds, farmyard manure being used in 

 large quantities. 



In view of all these variations in practice it will be 

 best to discuss a few general principles : — 



(i) Potatoes do not want an excess of nitrogenous 

 manure, because it renders them waxy and gives them 

 a tendency to boil a bad colour ; it also makes them 

 susceptible to disease. As quality is so important, the 



