354 



STATE BOARD OF AGRICULTURE. 



slightly soluble iu water and yet which are being used in the field quite 

 generally and with success, as sources of phosphoric acid, that the pres- 

 ent study is concerned. How are these insoluble compounds made solu- 

 ble and thus rendered available for the use of plants? Are microorgan- 

 isms in any way associated with this solvent action? 



Soil chemistry, soil physics and soil bacteriology are all probably 

 involved in the answer to such a question, since if microorganisms are to 

 thrive in the soil, the proper physical conditions must be maintained. 

 Again there are large numbers of inorganic and organic compounds in- 

 cluding the weaker acids which have their origin in microbic fermenta- 

 tions and which possess more or less solvent power. These are of in- 

 terest to the soil chemist. Many such compounds, however, must be ac- 

 counted for by the soil bacteriologist and naturally the problem shapes 

 itself into a study of the solution of insoluble phosphates by soil bacteria, 

 veasts and molds either directlv, on the one hand, or indirectlv, on 

 the other, by means of the solvents resulting from decomposition and 

 fermentation. 



Stoklasa (1) has shown that Avhen bone meal is employed as the 

 insoluble phosphate, it has been possible to get as much as 21.56% of 

 available phosphoric acid by inoculating a nutrient solution, phosphorus 

 free, with B. megaterium, to which 10 grams of finely ground bone meal 

 had been added. The bone meal he used contained 19.8% total phosphoric 

 acid, 5.26% nitrogen and 1.5% fat, which is considerably lower in 

 phosphoric acid and fat and higher in nitrogen than the average run of 

 bone meal met with in this country. This may account for the marked 

 difference between Stoklasa's results and those obtained in this labora- 

 tory. The following table taken from Stoklasa gives the results of his 

 experiments based upon ten grams of bone and 900 c. c. of nutrient 

 solution per flask inoculated with pure cultures and allowed to stand for 

 33 days. 



Table No. 1. Solvent action of pure cultures according to Stoklasa. 



Inoculation. 



Grams P20smade 

 soluble from 10 

 g. Bone meal. 



Per cent of the 



total P 2O 5 

 made soluble. 



Not inoculated 



B. megaterium 



B. fluorescens liquefaciens 



B. proteus vulgaris 



B. butyricus (Hueppe). . . 



B. mycoides 



B. mesentericus vulgatus. 



0.067 

 0.427 

 0.182 

 0.293 

 0.308 

 0.456 

 0.408 



3.83 

 21 . 56 



9.19 

 14.79 

 15.55 

 23.03 

 20.60 



Stoklasa explains the increased soluble phosphoric acid in the in- 

 oculated flasks as due to the proteolytic and diastatic enzymes incident to 

 the bacterial growth acting upon the insoluble tri-calcium phosphate of 

 the bone. 



To determine the action of these same organisms in soil, (2) he em- 

 ployed large unglazed pots filled with ordinary field soil in which oats 

 were planted as the test crop. 



To all but one of these, five grams of bone 



(1) Ueber den Einfluss dor Baktericn auf die Knochenzersotzung. Ccntralbl. f. Bakt., Abt. II Bd. 

 6. S. 526. (1900). 



(2) Ueber den Einfluss der Baktcrien auf die Knoclienzersetzung. Centralbl. f. Bakt., Abf II 

 Bd., 6, S. 554. (1900.) 



