6 PLANT PRODUCTS 



to be a weakness in the complete plant. Very much finer 

 division is in practice found to be necessary. Some years 

 ago the author demonstrated on a small scale that the usual 

 standard sieve for basic slag was about right. (See p. 25.) 

 When a slag was sieved and only those parts which refused 

 to pass a sieve with thirty meshes to the linear inch were 

 used as a dressing on grass land, no visible benefit resulted. 

 When the sieve was finer and contained sixty meshes to the 

 linear inch, the part that refused to pass produced a slight 

 effect. When the sieve contained one hundred meshes to 

 the linear inch, the part that refused, produced about half 

 the effect of a complete slag. When the part that passed 

 the sieve with one hundred meshes to the linear inch was 

 applied to the grass land the effect was good ; and when still 

 finer sieves were used, no further improvement could be 

 observed. In short, so far as basic slag on grass land is 

 concerned, it may be taken as certain that fertilizers of the 

 order of fineness, represented by just passing a sieve of the' 

 standard dimensions, are at their maximum efficiency. 

 As already stated above fertilizers do not travel laterally 

 in the soil, and in consequence even the soluble manures 

 require some degree of fine grinding, but not to the same 

 extent as in the case of the insoluble fertilizers. 



When the fertilizer is applied, whether by hand in broad 

 casting, or whether by a drill or other machine, it is desirable 

 that the fertilizer should be not merely finely divided, but 

 should also be in a dry condition. If the fertilizer is apt 

 to form lumps, all the energy expended on fine grinding is 

 wasted. Materials quite insoluble in water are not likely 

 to give trouble in this respect, but those that dissolve may 

 pick up moisture from damp air, and the surface of the grains 

 become coated with a strong solution, only to dry up later 

 in an atmosphere less moist, and thus cause the manure to 

 become caked. It is a well-known fact that dusty mercury 

 globules do not coalesce, and, similarly, it is a common 

 household recipe to add a minute amount of rice flour to 

 salt, so that it does not cake in damp weather. The sticky 

 grains become coated with a fine dust, and are no longer 



