August 18, 1916] 



SCIENCE 



247 



the soil on the solubility of phosphates is bet- 

 ter understood by a brief consideration of three 

 important and definitely recognized processes 

 that have long been known to bring about the 

 change of the nitrogen from the unavailable 

 form, as it occurs in the protein of clover, 

 manure, etc., to the readily available form of 

 the nitrate. 



(1) Ammonia Production. — The first process 

 results in the change of the organic nitrogen 

 to ammonia nitrogen. The ammonia is ab- 

 sorbed by the soil moisture and forms ammo- 

 nium hydroxid. Much carbon dioxid is pro- 

 duced at the same time and some of it, also, is 

 absorbed by the soil moisture and then unites 

 with the ammonia to form ammonium car- 

 bonate, which is alkaline. 



(2) Nitrite Production. — The second and 

 most important of the three stages consists of 

 the oxidation of the ammonia to nitrite by the 

 nitrite bacteria (Nitrosomonas) . The oxida- 

 tion of ammonia to nitrous acid by the nitrite 

 bacteria is represented by the following equa- 

 tion: 



(NHOjCCV-t- 60 = 2HN0 2 + H 2 CO B + 2H 2 0. 



The ammonium portion of the ammonium 

 carbonate has been converted into nitrous acid 

 and carbonic acid has been set free. Both 

 these acids will combine with some base. It is 

 important to note that nitrogen of the alkaline 

 substance, ammonia, has been converted, or 

 transformed, by the biochemical removal of 

 hydrogen and addition of oxygen into a 

 strongly acid substance, nitrous acid. 



The primary purpose of this investigation is 

 expressed in the question, "Will the calcium of 

 pure rock phosphate, Ca 3 (P0 4 ) 2 , suffice as a 

 base; and, if so, will the phosphorus be made 

 soluble? This will be answered by the experi- 

 mental data reported in another part of this 

 publication. 



If nitrite production takes place with tri- 

 calcium phosphate as a source of the base 

 calcium, then the reaction must be represented 

 by one of the following equations : 



Ca,(P0 1 ) 2 -t- 2HN0 2 = Ca 2 H 2 (PO,) 2 + Ca(N0 2 ) 2 



Ca^PO.,), + 4HN0 2 = CaH.,(P0 4 ) 2 + 2Ca(NO,) 2 . 



(3) Nitrate Production. — The third and last 

 stage is a simple oxidation of the nitrite to 

 nitrate by the action of nitrate bacteria (Nitro- 

 bacter). It consists in the addition, by bio- 

 chemical action, of oxygen to the nitrite: 



Ca(N0 2 ) 2 + 20 = Ca(NO,) a . 



This reaction increases neither acidity nor 

 akalinity, and no liberation of insoluble com- 

 pounds would be expected in this process, as no 

 additional base is necessary, as seen by refer- 

 ence to the equation. 2 



INFLUENCE OP AMMONIA PRODUCTION ON SOLU- 

 BILITY OF PHOSPHATES 



The most important product formed in the 

 first process, or stage, of the decomposition of 

 organic matter is ammonium carbonate. The 

 ammonium carbonate is alkaline, and conse- 

 quently could not be expected to exert any 

 action on the solubility of raw rock phosphate. 



In 1904 Stalstrom, of Finland, conducted 

 laboratory experiments on the solubility of 

 pure rock phosphates with bacteria which pro- 

 duced ammonium carbonate from peat and 

 from manure containing peat litter. He con- 

 cluded that there was no appreciable increase 

 in solubility of phosphorus where the bacteria 

 had produced ammonium carbonate over the 

 sterile treatments in which no ammonium car- 

 bonate was produced. His experiments lasted 

 forty-two days and were under conditions 

 which would permit of determining soluble 

 phosphorus, were it present. His work is ex- 

 tremely interesting as it demonstrates that in 

 the first stage of decomposition it has been 

 impossible to measure any soluble phosphorus 

 without the growing plant as an indicator. 



Similar results have been obtained by the 

 Ehode Island and Wisconsin Experiment Sta- 

 tions in attempts to detect soluble phosphorus 

 in fermenting mixtures of manure and raw 



~ The results of an experiment to test the effect 

 of the nitrate bacteria on pure tricalcium phos- 

 phate support the theory that no solution of phos- 

 phorus is to be expected by the action of nitrate 

 bacteria. 



