288 Bacteria in Relation to Country Life 



calcic (four-lime) form, and shows a high rate of availa- 

 bility under suitable soil conditions. 



The use of Thomas slag yields particularly gratifying 

 returns on light open soils containing an abundance of 

 humus. It seems that the open character of the soil, 

 by encouraging the bacterial decomposition processes, 

 makes possible the formation of large quantities of 

 carbon dioxid and of other substances which help to 

 make soluble the phosphate in the slag. Thomas slag 

 has been found to be particularly acceptable on light, 

 soils, on which green-manuring is systematically resorted 

 to. Schultz, of Lupitz in Germany, celebrated for his 

 systems of green-manuring, employed Thomas slag for 

 many years and found it a suitable as well as economical 

 source of phosphoric acid. The great masses of legumi- 

 nous catch-crops turned under by him offered splendid 

 opportunities for intense bacterial changes and for the 

 formation of abundant amounts of available phosphoric 

 acid. 



Other sources of phosphoric acid. — In the case of green- 

 manures, animal manures, and of commercial fertilizers 

 of organic origin, such as ground fish, meat meal, 

 tankage, castor pomace, and the Hke, the bacterial 

 reactions, in so far as the phosphoric acid is concerned, 

 are of the utmost importance. The barnyard manures, 

 so extensively employed in general and special farming, 

 contain their phosphoric acid in insoluble combinations. 

 The solid excreta and the Utter containing nearly all 

 of the phosphoric acid of the manure must first undergo 

 decay in order that they may yield available plant-food 

 to the crops. What the particular reactions through 



