SOILS FERTILIZERS. 423 



Quantitative relationships of carbon, phosphorus, and nitrogen in soils, 

 R. Stewart (lUinois Sta. Bui. I'/o, pp. 91-121). — The literature of investigations 

 ou carbon, nitrogen, and phosphorus in soils is reviewed, and a bibliography of 

 82 references is given. 



A study of the relationship of carbon, phosphorus, and nitrogen in certain 

 Illinois soils, particuhirly that of the southern Illinois experimental farm, is 

 reported, special attention being given to methods of determining the organic 

 matter and associated mineral matter in the soils. The results of this study 

 are summarized as follows: 



" The phosphorus-nitrogen ratio in the surface soil of the brown silt loam 

 soils is 1 : 13.5 while the same ratio in the black clay loam soils is 1 : 11.4. 



" Under normal conditions the nitrogen-carbon ratio of the soil has a tendency 

 to become narrower as the age of the organic material increases; the ratio, 

 however, never becomes narrower or even equal to the ratio of the more common 

 proteins contained in the humus-producing materials. 



•' The nitrogen-carbon ratios of the ordinary brown silt loam soils of Illinois 

 are 1 : 12.1, 1 : 11.5 and 1 : S.9 in the surface, subsurface, and subsoil respectively. 

 The ratios in the black clay loam soils are 1 : 11.7, 1 : 11.9 and 1 : 9 in the 

 surface, subsurface, and subsoil respectively. 



" The phosphorus-carbon ratio in the surface soil of the brown silt loam is 

 1 : 165.2 while the ratio in the surface soil of the black clay loam soils is 1 : 163.6. 



" The calculation method for determining organic phosphorus is very cou- 

 serAative in character and can be relied upon in drawing broad general con- 

 chhsions. 



" The evaporation on the water bath of the ammoniacal solution, in the 

 preparation of the "matiere noire" in quantity for analysis, causes a hydrolysis 

 of the organic phosphorus compounds. 



" The determination of the phosphorus associated with the precipitated 

 " matiere noire " is not a quantitative method for the determination of the total 

 organic phosphorus of the soil. It should be regarded only as a good qualita- 

 tive evidence of the existence of organic phosphorus in the soil. 



" The contention of Fraps that, ' There is no evidence that the phosphoric acid 

 in the filtrate is in organic combination ' and that, ' it is probably derived from 

 the iron and aluminium phosphates ' is entirely untenable." 



Active phosphoric acid and its relation to the needs of the soil for phos- 

 phoric acid in pot experiments, G. S. Fraps (Texas Sta. Bui. 126, pp. 7-72, 

 figs. 2, charts 4). — The work reported in this bullethi dealt with (1) the phos- 

 phoric acid of the soil and the nature of the phosphatic componnds dissolved by 

 weak solvents, and (2) pot experiments comparing analytical and crop results — 

 the relation between productiveness and "active" (soluble in fifth-normal 

 nitric acid) phosphoric ficid. In the course of the work a study was made of 

 the solubility of a number of mineral phosphates which may occur in soils, 

 including various calcium, iron, and aluminum phosphates, and of the fixation 

 of phosphates in soils. 



The pot experiments were not all conducted in exactly the same manner, but 

 the general procedure was as follows: 



'• Washed gravel was added in sutficient amounts to an 8-inch Wagner pot to 

 make the total weight 2 kg. Five kg. of soil was then added. The soil had been 

 previously pulverized in a wooden box with a wooden mallet until it would 

 pass a 3 mm. sieve, gravel being removed. 



"The addition of fertilizer consisted of 2* gm. of acid phosphate, 1 gm. ni- 

 trate of soda, and 1 gm. sulphate of potash. In later experiments 1 gm. of 

 ammonium nitrate was used in place of nitrate of soda. If the size of the crop 

 appeared to render it necessary, more nitrate of soda or sulphate of potash was 



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