SECTION VI. COMPOUND MANURES 



Ammoniated Superphosphate. This very useful com- 

 pound manure is obtained by mixing the requisite quantities 

 of superphosphate and sulphate of ammonia. To make a 

 mixture containing i % of nitrogen, 19 cwt. of superphos- 

 phate and i cwt. of sulphate of ammonia should be used. 

 Mixtures containing 7 % of nitrogen, made from 13 cwt. 

 of superphosphate and 7 cwt. of sulphate of ammonia, are 

 occasionally used, but only for very special purposes. The 

 superphosphate is weighed out according to the calculated 

 amount, placed in a heap, and levelled, the sulphate of 

 ammonia is also weighed out, placed on the top of the super- 

 phosphate heap and levelled. A man now digs vertically 

 down into the heap and transfers this mixture to a barrow, 

 which is wheeled away and worked through a J-in. screen. 

 When it is all passed through, the screen is exchanged for a 

 [-in. screen, and passed back again. By digging vertically, 

 so as to obtain a fair sample from top to bottom at all stages 

 of the process, the mixing becomes very complete. Special 

 machines, "batch mixers," "pulver blenders," or " pulvo 

 mixers," can now be obtained to save much of the labour 

 involved. The superphosphate and sulphate of ammonia 

 should be weighed out as before, but can be wheeled straight 

 away to the cups of an elevator which delivers the mixture 

 to the hopper on top of the pulvo mixer. On falling into 

 the pulvo mixer, revolving arms blend the material and throw 

 it against screens, through which the fine material passes, to be 

 promptly bagged at the spout of the pulvo mixer. 



Sulphate of ammonia checks the retrogression of super- 

 phosphate (p. 154). Should such a mixture show any 

 slight tendency to cake, it can be easily broken by passing 

 through a screen. As a rule any such tendency to cake is 



