PHOSPHORUS 177 



is found in the ash of these organisms in such large quantities. The 

 phosphorus, on the death of the organism, would be returned to the 

 soil in a readily available form, for Stoklasa has found that 50 per 

 cent, of the nitrogen of these organisms is nitrified within six weeks, 

 and there is no reason for 'believing that the phosphorus would be 

 liberated much more slowly. Then there is the possibility that many 

 of the constituents of the bacterial cell may become available, 

 through the action of autolytic enzymes without the intervention 

 of other bacteria. 



It is further evident that an organism which possesses the power, 

 when growing under appropriate conditions, of generating 1.3 times 

 its own body weight in carbon dioxid during twenty-four hours, as 

 does the Azotobacter, must greatly change the composition of the 

 media in which it is growing. Water charged with carbon dioxid 

 is a universal solvent and will attack even ordinary quartz rock. 

 Granite and rocks related to it are rather quickly attacked, with the 

 liberation of potassium and other elements. Carbonated water 

 would act upon the tricalcium phosphate of the soil with the forma- 

 tion of more readily soluble phosphates, for this substance is four 

 times as soluble in water charged with carbon dioxid as it is in pure 

 water: 



Ca 3 (PO4) 2 + 2CO 2 + 2H 2 O = Ca 2 H 2 (PO4)2 + Ca(HCO 3 ) 2 



Moreover, the nitrogen-fixing organisms form, among other 

 products, formic, acetic, lactic, butyric, and other acids. The kind 

 and quantity of each depends upon the specific organisms and upon 

 the substance on which they are acting. These substances are sure 

 to come in contact with some insoluble plant-food which may be 

 rendered soluble, for they have a highly solvent action on the 

 insoluble phosphates. The resulting salts of calcium would be 

 further attacked by bacteria, with the formation of calcium car- 

 bonate. 



Whether these processes will give rise to an increase in the water- 

 soluble plant-food of the soil depends upon whether the products 

 of the second, the analytic reactions, exceed the products of the 

 first, the synthetic reactions. It must not be forgotten that, 

 although many of the organic phosphorus constituents may not be 

 soluble in pure water, they may be more available to the living plant 

 than are the constituents from which they were at first derived 

 through bacterial activity. 



This being the case, variations in the results reported from 

 laboratory tests are to be expected. Stoklasa found that bacterial 

 activity rendered the phosphorus ot the soil more soluble, whereas 

 Severin, in his early work, found the opposite to be true. Others 

 have found that the solvent action of bacteria for insoluble phos- 

 phates is in direct proportion to the acid secreted by the organism. 

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