COMPOUND MANURES 185 



of the seeds. The top dressings of sodium chloride and 

 nitrate of soda easily wash out of the soil, and are mostly 

 required at periods in the life of the plant between germina- 

 tion and flowering ; but flowering is not reached in the 

 mangold crop. The late application of these ingredients 

 permits the farmer to reduce the risk of " bolting " in man- 

 golds, an advantage which would be lost if all the ingredients 

 were applied before sowing the seed. 



Complete Manures. Occasionally manures of a complete 

 character are required. The operation of compounding 

 complete manures presents no special difficulties beyond 

 those alluded to in describing the manufacture of ammoniated 

 superphosphate and potassic superphosphate. For making 

 these compounds some kind of mixing machine is needed ; 

 either a revolving wheel with several pegs, or a disintegrator, 

 or a pulvo mixer (see pp. 116, 179). Care must be taken 

 that rock phosphates, or other material containing calcium 

 carbonate, must only be used sparingly, to avoid the excessive 

 reversion of superphosphate, unless a large proportion of 

 insoluble phosphate is asked for. When several ingredients 

 are mixed, the advantage of various forms and degrees of 

 solubility can readily be obtained. The most important 

 materials for compounding are superphosphate, bone flour, 

 sulphate of ammonia, potash salts and rape dust, all of which 

 can be blended together very satisfactorily. Rape dust is 

 very useful in checking " setting " in a compound manure 

 (see p. 180) ; very fine, dry materials, which do not clog 

 any type of machine, can be made in this way. It is better 

 to leave nitrate of soda out altogether, but both salt and 

 gypsum may be used in mixtures if needed. 



It is quite clear that on certain types of soil the advantage 

 of superphosphate has been somewhat exaggerated. A 

 considerable portion of the phosphates may be of a far less 

 soluble form without any disadvantage at all. This fact 

 is very well illustrated by Hendrick, who collected the average 

 of 66 field experiments carried out during the years 1911-14 

 throughout several of the northern counties of Scotland. 

 The most important of these results are represented in 



