208 ANNUAL EEPOETS OF DEPARTMENT OF AGRICULTURE. 



Tlie occurrence of surface deposits of nitrates, especially in the 

 arid and semiarid sections of the United wStates, is quite common and 

 has led to many vain hopes. A number of these deposits have been 

 investigated. Ahnost always the "find" is a surface deposit only; 

 none has been found of large commercial importance, and even when 

 sufhciently abundant to justify a local exploitation in itself the 

 deposit is usually so situated as regards a water and fuel supply as 

 to render working it impracticable. 



PHOSPHATES. 



It has been shown that the United States contains hi^h-grade 



Ehosphate deposits of such magnitude as to be practicafly inex- 

 austible. Phosphates are the basis of commercial fertilizers the 

 world over, but changing economic conditions, not only m the 

 United States, but throughout the world, are making it desirable 

 and probably necessary radically to change existing methods of 

 manufacturmg and marketing phosphates. The cheap production 

 of ammonium phosphate is the ideal sought. 



The bureau has been investigating improved methods of obtain- 

 ing phosphoric acid by means of sulphuric acid, and it is carrying on 

 investigations looking to the combined production of phosphoric 

 acid and ammonia by electrical processes. Meanwhile, an investi- 

 gation has been undertaken of the economic justification for the 

 growing use of untreated phosphate rock and also of the possibility 

 of economical decrease of wastage in mining. 



LIME. 



The use of lime in soil management is increasing greatly in this 

 country. Fortunately large deposits of limestone admirably suited 

 to the production of agricultural hmes are to be found widely dis- 

 tributed throughout the United States, and the teclmology of the 

 different forms of lime production is already highly developed. 

 The bureau has during the past year made some important and 

 fundamental studies on the absorption or fixation of lime by the 

 particles in the soil, showing that it has generally an important 

 effect on the absorption or fixation of other water-soluble fertilizers, 

 and that the different forms of lime have distinctly different effects 

 on the flocculation or crumbling of the soil, so that these different 

 forms should not be used indiscriminately where the control of 

 tilth is important. 



COMPOSITION OF SOILS AND PLANT ASH. 



Increasing evidence of the great mineral complexity of agricul- 

 tm'ally useful soils has been accumulated and chemical evidence 

 gathered that, with an occasional exception here and there, practically 

 all soils suitable for crop production contain estimable quantities 

 of all the mineral elements for which there are rehable methods of 

 analysis. Incidentally it has been shown that radium and radio- 

 active substances are present normally in soils to amounts in excess 

 of that which could possibly be applied artificially and at the same 

 time economically. And the same statement can be made in general 

 for the so-called catalytic fertihzers or "activators." The work on 



