204 CHEMICAL FERTILIZERS 



and the clover may be replaced by one, two, or three years-' 

 seeds mixture, consisting of various grasses, with red clover 

 if it is for a short period, and wild white clover if it is intended 

 to last out for three years. In very poor lands this period 

 may be even increased by cutting hay for two years and 

 grazing subsequently for several years. On rather richer 

 lands wheat may be taken after the rotation previous to 

 barley. Where the hay crop is extended it is desirable that 

 this crop should receive more generous manuring, especially 

 with phosphates ; where the land is deficient in lime it is 

 advantageous at this period to use 8-10 cwt. of slag. On 

 light lands, especially those in poor condition, some sulphate 

 of ammonia should be applied to the barley crop and some 

 potash manure used for the hay crop. In the experiments 

 on rotations at Cockle Park, Northumberland, good results 

 have been obtained by using all the farmyard manure for the 

 cereal crop, and all the artificials for the hay crop. In this 

 case the hay received 25 Ibs. of nitrogen, 75 Ibs. of phos- 

 phoric acid and 50 Ibs. of potash per acre, which could also 

 be supplied by using 7 cwt. of a mixed fertilizer, containing 

 about 3|% of nitrogen, 21% of calcium phosphate and 6J% 

 of potash. 



On very heavy clay soils rotations may follow the old 

 three-course system of wheat, beans and bare fallow, or 

 its modern improvement of replacing the bare fallow by a 

 turnip crop, or a smother crop, rape, cabbage, tares, etc. In 

 the southern counties of England, where the summers are 

 warmer and longer than in the other parts of Great Britain, 

 an improvement has been made by introducing a catch crop 

 during the winter after wheat and before turnips. This 

 catch crop of tares or rape is generously manured with full 

 supplies of superphosphate, sulphate of ammonia and 

 potash salts, and is consumed on the ground by sheep in 

 the following spring. This system works very well in the 

 South Downs, where sheep are kept on the higher levels 

 for grazing, taken down in the winter to the low-lying fields 

 of vetches or other green fodder, which provide the ewes 

 and lambs with a plentiful supply of food in the early months 



