238 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1952 



of cereal plants for feeding man and his domestic animals upon the 

 seeds or grain, those parts of the plant in which most of the soil- 

 derived phosphorus is concentrated. As proportions of total mineral 

 needs, man and animals require more phosphorus than plants (about 

 24 percent compared with 16 to 17 percent) . The fact that seeds are 

 concentration centers for the phosphorus in plants is a major reason 

 for the development of cereal grains (wheat and rice) as primary foods 

 for the animal kingdom. But as a result far more phosphorus was 

 removed from soils than was returned. Early farming was nomadic, 

 a steady movement from soils whose fertility had been extracted to 

 virgin soils maintained in a state of mineral sufficiency by the cycles 

 which circulate nitrogen, phosphorus, and other elements. Three 

 devices were in time discovered: (1) Returning animal manures to 

 soils; (2) fallowing, i. e., periodic and temporary returns to the 

 natural cycles ; (3) crop rotation. But none of these could indefinitely 

 return a sufficient amount of phosphorus to soils as human populations 

 increased and sharpened the demands for cereal foods. 



In the seventeenth and eighteenth centuries the usefulness of bones 

 as a fertilizer was gradually realized, particularly when it was found 

 that their effectiveness was increased if they were first ground finely. 

 But it was not until 1795 that the first suggestion was made that the 

 principal virtue of bone material lay in its phosphorus content; nor 

 did this become really understood until Liebig in 1840 published his 

 theory of mineral plant nutrition. Nevertheless, bones were exten- 

 sively used as a fertilizer before 1840, particularly in England. Thus 

 in 1815 we find Liebig attacking England for her bone-importing 

 activities : "England is robbing all other countries of their fertility. 

 Already in her eagerness for bones, she has turned up the battlefields 

 of Leipzig, Waterloo, and the Crimea ; already from the Catacombs of 

 Sicily she has carried away the skeletons of many successive genera- 

 tions . . ." 



It was Liebig himself who indirectly solved the problem of bone 

 supply. He suggested that treatment of bones with strong acid would 

 give a more soluble phosphatic fertilizer. In England Lawes put this 

 idea into practice, thus founding the superphosphate industry. Find- 

 ing the supply of bones inadequate to meet the demand for super- 

 phosphate, Lawes experimented with phosphorus-containing minerals 

 and found that an equally effective superphosphate could be based 

 upon these mineral sources. 



The existence of richly phosphatic mineral deposits in various 

 parts of the world is not a fortuitous legacy from the earth's original 

 formation by solar condensation. These deposits exist as a result of 

 the marine-cycle movements of phosphorus. It is not fully under- 

 stood why these exceptional concentrations of mineral phosphates 



