68 THE CHEMISTRY OF THE FARM 



such cases very suitable. If top dressings of soluble 

 manures are used for soils of this class they should be 

 applied later than for soils holding a greater volume of 

 water. 



Some complications may arise when farmyard manure 

 is applied with artificial manures. Neither nitrates or 

 ammonium salts give their best results when placed in 

 contact with fermentable organic matter in the soil. 

 The possibility of loss is greatly diminished by using 

 well-rotted manure, and may be still further prevented 

 by applying the nitrate subsequently as a top dressing. 

 Salts of potassium and sodium, superphosphate, and 

 sulphate of ammonium, should not be sprinkled on the' 

 dung in the furrow, but either mixed with the soil 

 before the dung is carted on, or (if the crop is grown 

 on the flat) sown broadcast after the dung is ploughed 

 in, and before harrowing (see p. 63). 



Return for Manure Applied.— No dressing of manure 

 is completely taken up by the crop to which it is 

 appHed ; dressings larger than the actual requirements 

 of the crop must therefore be employed to obtain a 

 given result. At Kothamsted, with a moderate dress- 

 ing of nitrate of sodium to barley, together with a 

 liberal supply of ash constituents, about 60 per cent, 

 of the nitrogen has been on an average recovered in 

 the increased produce. A much larger proportion is 

 recovered in good seasons. With mangels, manured 

 in a similar manner, about 62 per cent, of the nitrogen 

 in the nitrate of sodium has been on an average 

 recovered in the increased produce of roots obtained, 

 the nitrogen in the leaves being not reckoned, as they 

 ^re returned to th^ soil, In the absence of a full 



