FARM MANURES 579 



pounds of acid phosphate, and 125 pounds of potassium 

 chloride. This is equivalent to the addition of 485 

 pounds of an approximately 10-2-12 ready-mixed ferti- 

 lizer. Moreover, from the fact that so large an amount 

 of the plant-food carried is not readily available, it acts 

 as a residuum, which is slowly given up to the succeeding 

 crops. It has been shown in England * that paying in- 

 creased returns may be obtained from manure four years 

 after its application. At Rothamsted, England, 2 a 

 residual impetus was noticeable on crops forty years after 

 the soil was manured. This, however, is an exceptional 

 case. 



Farm manure may act as an indirect fertilizer in its 

 tendency toward improved physical relations. The addi- 

 tion of organic matter is the vital factor here. Better 

 tilth, better aeration, improved drainage, and increased 

 water capacity are the necessary accessories to a rise in 

 humus content. The influence of manure on the avail- 

 ability of the mineral constituents of the soil is not the 

 least of its indirect effects. Even the increased adsorp- 

 tive power of the soil should be mentioned, in its tendency 

 toward the counteraction of toxic principles. 



Another general characteristic of average farm manure 

 is that, while it is a fertilizer, it is an unbalanced one. 

 Proportional very roughly to a 10-2-12 commercial mix- 

 ture, any one acquainted with general fertilizer practice 

 can see that it is too high in nitrogen and too low in avail- 

 able phosphoric acid. The elimination of such a condi- 



1 Voelcker, J. A., and Hall, A. D. The Valuation of Unex- 

 hausted Manure Obtained by the Consumption of Foods by 

 Stock. London. 1903. 



2 Hall, A. D. Fertilizers and Manures, p. 213. New York. 

 1910. 



