VV.LY AGRICULTURE. 



with it rapidly dissolves, among other things, the soluble 

 monocalcjc phosphate and carries it down into the soil 

 layer where it immediately undergoes what may be called 

 an extensive reversion. In other words it meets various 

 compounds of calcium, iron and aluminium and reacts 

 with them forming compounds which are only very 

 sparingly soluble in soil water. There is therefore little 

 chance of phosphate being washed out of land and lost in 

 drainage, which fact is usually expressed by saying that 

 the fixation of soluble phosphate in soil is very complete. 

 At first glance it would appear as if, with the return of 

 the phosphate to the insoluble state, the labour of the 

 manufacturer had been thrown away, but it must be 

 remembered that although again practically insoluble in 

 pure water, the phosphate is now spread in a very fine 

 state of division over the surfaces of an enormous number 

 of soil particles. It has therefore a much better chance of 

 being acted upon by the soil water and rendered available 

 than in its former state of solid particles however finely 

 ground. Again the mixing with the soil particles is 

 much more intimate than could ever be attained by 

 sowing ground phosphate on land and working it in. 



Superphosphate is a useful manure for practically all 

 crops, its application being particularly beneficial in the 

 case of roots, where rapid early growth is desirable. It is 

 best employed on land fairly well supplied with lime on 

 account of its acid character. With soils poor in lime, 

 ground phosphate or basic slag is to be preferred. The 

 quantity applied is usually about two hundred kilograms 

 por fed dan. 



