FARM MANURE 



531 



moist in order to prevent loss of ammonia and to encourage 

 vigorous bacterial action. Acid phosphate or raw rock phos- 

 phate and a potash fertilizer are often added, to balance up 

 the mixture and make it a more effective fertilizer. Lime is 

 also introduced, to react with such organic acids as may tend 

 to interfere with proper decay. Undecayed plant tissue, 

 such as sod, leaves, weeds, grass, sticks, or organic refuse of 

 any kind, may thus be changed slowly to a form which will be 

 valuable in building up the soil and in nourishing plants. 

 Even garbage may be disposed of in such a manner. 



306. Residual effects of manure. — No other fertilizer 

 exerts such a marked residual effect as does farm manure. 

 As it is applied in large amounts, its physical and biological 

 influences are of necessity very great and persist for a con- 

 siderable time. As only about one-half the nutrients of farm 

 manure are readily available, the residual effect of its fertiliz- 

 ing elements carry over into succeeding years. Hall x pre- 

 sents the following comparative data regarding the recovery 

 of nitrogen from various fertilizers. The crop used was man- 

 golds. The low recovery of the nitrogen from the manure is 

 of especial note. There is no reason to believe that the pot- 

 ash of the manure would be any more readily available and 

 the phosphoric acid would certainly show a lower recovery. 



Table CXXI 



RECOVERY OF NITROGEN IN A CROP OF MANGOLDS. 



Sodium nitrate .... 

 Ammonium salts . . . 



Rape cake 



Farm manure 



Bate to 

 the Acre 



550 lbs. 



400 lbs. 



2000 lbs. 



14 tons 



Yield in 

 Tons 



17.95 

 15.12 

 20.95 

 17.44 



Percentage 



Eecovery of 



Nitrogen 



78.1 

 57.3 

 70.9 

 31.6 



1 Hall, A. D., Fertilizers and Manures, p. 210; New York, 1921. 



