388 SOILS 



of unleached ashes should contain 8 per cent, of 

 potash and 2 per cent, of phosphoric acid ; in such 

 a case each plant food should be figured out 

 independently. If a fertiliser containing 10 per 

 cent, of potash and 5 per cent, of phosphoric acid 

 is needed, and ashes can be bought very reasonably, 

 it will only be necessary to add to the ashes 

 a sufficient quantity of muriate of potash, and of 

 superphosphate, for example, to make a fertiliser 

 having the desired analysis. 



The actual mixing of fertilisers is easily done. 

 The right quantities of the several materials are 

 dumped upon a tight, smooth floor and are shovelled 

 over until thoroughly mixed. The mixture may 

 then be put through a sieve. It is best to keep the 

 several ingredients separate until a short time 

 before the fertiliser is needed. Any fertiliser con- 

 taining ammonia should not be mixed with lime, 

 as lime attacks ammonia and nitrogen escapes. 

 If highly concentrated fertilisers are mixed, as 

 muriate of potash and bone ash, it is often de- 

 sirable to add a quantity of some other material, 

 not plant food, as dust, dry soil or land plaster. 

 This gives the mixture greater bulk so that it can be 

 distributed much more evenly, especially if light 

 applications are to be made. The saving in buying 

 raw materials and mixing them at home is often 

 25 to 40 per cent, over the cost of the same amounts 

 of plant food if bought in the average manufactured 

 article. 



WHAT KINDS OF FERTILISER TO USE 



There are two great problems in using com- 

 mercial fertilisers. The first is, "What kind and 

 what amounts of plant food does my soil need?" 



