FAEM MANURE 505 



both as to the amounts of nutrients carried and as to their 

 availability. Because of the large acre applications of ma- 

 nure commonly made, the fertilizer constituents added in ma- 

 nure are considerable. Ten tons of farm manure, even if only 

 one-half its ammonia, one-sixth of its phosphoric acid and one- 

 half of its potash were readily available, are equal in fertil- 

 izing value to 333 pounds of sodium nitrate, 52 pounds of 

 acid phosphate, and 416 pounds of kainit. This equiva- 

 lent to the addition of 801 pounds of a readily available mix- 

 ture of fertilizer salts. This calculation, however, ignores 

 an equal quantity of nutrients which remain in the soil as 

 a residuum and may be used by succeeding crops. This resi- 

 dual effect of manure is generally a paying one during the 

 period of an ordinary rotation. 



Farm manure acts as an indirect fertilizer in that it adds 

 to the soil organic matter and thus improves the physical 

 condition of the land. "While it may not increase the organic 

 matter of the soil, because of the loss of carbon by exhalation 

 and leaching during the period of crop growth, its use materi- 

 ally influences the rate of reduction. Better aeration, drain- 

 age and bacterial activity ^ of necessity result from such an 

 addition. The influence of manure on the availability of 

 the mineral constituents of the soil is not the least of its 

 indirect actions. The fact that rock phosphate when mixed 

 with manure seems to have a higher availability bespeaks 

 a considerable solvent activity. The tendency of farm 

 manure to alleviate toxic conditions, such as alkali and acid- 

 ity, deserves attention. 



286. Outstanding cliaracteristics of farm manure. — ^As 

 farm manure is essentially a fertilizer, whether it is pro- 

 duced on the farm or purchased outright, it is logical to con- 

 trast it with the ready-mixed materials on the market. In 



^Oonn, H. J., and Bright, J. W., Ammomfication of Manure %n 

 Soil; Jour. Agr. Ees., Vol. XVI, No. 12, pp. 313-350, Marcli, 1919. 



Fulmer, H. L., and Fred, E. B., Nitrogen Ass%mulating Organisms %n 

 Manure; Jour Bad, Vol. II, No. 4, pp. 423-434, 1917. 



