Phosjjhorus. 387 



especially the superticial soils. Whether or no the total PjO., 

 in superficial soils plus sub-strata and sub-sub-strata, could we 

 go deep enough, would be found to be lower than other coun- 

 tries it IS hard to say, and the knowledge would be well nigh 

 useless even were it possible. It is the available phosphorus 

 which is the important thing, and if the available amount be 

 small it matters little how large the inaccessible amount may 

 be. In an extremely interesting paper (22) Dr. Cherry gives 

 some possible causes for this deficiency. He points out the 

 cycle by means of which inorganic rock phosphate fairly deep 

 in the ground becomes converted into inorganic bone phos- 

 phate, and finally laid down superficially on the ground. The 

 deep ground phosphate is dissolved by the acid juices of plant 

 roots, absorbed and assimilated, becoming part of the plant 

 substance. The plant will be either eaten by an animal and its phos- 

 ])horic acid concentrated in the bony framework of the animal, 

 which in the natural course of events will eventually die, and its 

 skeleton after the organic matter has become oxidised be left 

 deposited on the ground as superficial, easily-available phos- 

 phate ; or else the plant untouched will also in time die, and a 

 large amount of phosphorus stored in the leaves, fruit, bark 

 and wood will be deposited superficially. 



Since animals feed on plants there must of necessity be a 

 continual struggle for survival, so that the larger and more 

 numerous the animals are in any place, the greater will be the 

 plant growth to keep pace, and consequently the roots will 

 penetrate deeper into the earth and amongst other things a 

 larger amount of phosphoric acid, hitherto deep buried and 

 non-available, will become superficial and easily available. The 

 low percentage of phosphoric acid in Australian soils is attributed 

 by Dr. Cherry to the fact that Australia has never had any 

 large land animals. Certainly there have been discovered near 

 Lake Eyre, South Australia, areas of phosphate deposit, but 

 these are prol)al)ly due to crocodile fossils, and not to land 

 animals. 



Let us now view the state of aifairs at the present day. 

 Australia has opened out largely as a grazing country. This 

 opening out has had two effects: — 



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