532 NATURE AND PROPERTIES OF SOILS 



The length of time through which the effects of an appli- 

 cation of farm manure may be detected in crop growth is 

 very great. Hall 1 cites data from the Rothamsted Experi- 

 ments in which the effects of eight yearly applications of 14 

 tons each were apparent forty years after the last treatment. 

 This is an extreme case. Ordinarily, profitable increases may 

 be obtained from manure only from two to five years after 

 the treatment. 2 The fact remains, nevertheless, that of all 

 fertilizers, farm manure is the most lasting and lends the most 

 stability to the soil. 



307. The place of manure in the rotation. 3 — With 

 trucking, garden, and greenhouse crops, the applications of 

 large amounts of manure year after year have proven advis- 

 able. As a matter of fact, manure has shown itself, especially 

 if balanced with phosphoric acid, to be the best fertilizer for 

 intensive operations. This is due not only to the nutrients 

 carried by the manure, but to the large amounts of easily 

 decomposed organic matter that are at the same time intro- 

 duced. In a rotation involving the staple crops, such as maize, 

 oats, wheat, hay, and the like, less intensive applications are 

 advisable, not only because of a lack of manure but because 

 the return to a ton of manure applied must be raised as high 

 as possible. On the average farm, there is less than one ton 

 of manure produced to an acre of arable land. Moreover, the 

 return from manure will vary according to its place in the 

 rotation. This has proved to be the case with commercial 

 fertilizers and the fact is becoming more and more apparent 

 with farm manure. 



In general, meadows and pastures derive more benefit from 

 manure, either residually or directly, than any other crop. 



1 Hall, A. D., Fertilizers and Manures, p. 213; New York, 1921. 



a Voelcker, A., and Hall, A. D., The Valuation of Unexhausted 

 Manure Obtained by the Consumption of Foods by Stock: London, 

 1903. 



3 See Thorne, C. E., Farm Manures, Chaps. XI and XIII, New York, 

 1914. 



