Artificial Maniiies 313 



Artificial Manvres 



With the introduction of machine power to replace horse and other 

 animal power, the amount of stable manure available to the farmer 

 was appreciabl)' reduced. Furthermore, the growth of large urban 

 areas recjiiired intensive truck-garden systems which consumed large 

 quantities of the available manure. This resulted in a decrease in 

 the amount left for use in fields and gardens. Recourse was had, 

 therefore, to composting plant residues with mineral fertilizer, result- 

 ing in a product similar in every respect to that obtained from stable 

 manures. To distinguish such composts of plant residues from com- 

 posts of stable manures, the former are usually designated as "arti- 

 ficial manures." 



To prepare artificial manures similar in chemical composition and 

 in their effects upon the soil to composts commonly obtained from 

 stable manures, cereal straw or other plant residues are utilized. 

 These are supplemented with an inorganic source of nitrogen and to 

 some extent also with available phosphorus and lime. When they 

 are properly moistened, decomposition of the composts sets in im- 

 mediately and is accompanied by a rise in temperature. The micro- 

 biological population and the chemical processes of decomposition 

 involved are similar to those which commonly are found in like com- 

 posts of stable manures. The value of inoculating such composts 

 with active microorganisms is still debatable. Some fresh garden 

 soil or actively decomposing stable manure is occasionally used for 

 inoculation, with very satisfactory results. 



The rapidity of decomposition of the plant materials in the com- 

 post and their transformation into humus depend upon the nature 

 of the materials; their chemical composition; the amount and nature 

 of the inorganic nutrients added, especially the nitrogen; the mois- 

 ture content of the compost; its proper aeration; and temperature. 

 These factors also influence the chemical nature of the humus pro- 

 duced in the compost and its effect upon soil processes. The nature 

 of the plant residues and the conditions and extent of decomposition 

 are particularly important. The humus of a compost produced from 

 cereal straw will, therefore, vary from that formed from corn stalks, 

 or from oak leaves, or from pine needles, or from soybean stover 

 (Table 70). 



The compost is usually turned several times, especially after a 

 temperature of 65-80° C has been attained. The turning must be 



