590 SOILS: PROPERTIES AND MANAGEMENT 



This commercial evaluation, of course, must be applied 

 with care because of the many factors tending to vary 

 the composition of the excrement. Litter, particularly, 

 will exert a great influence in this direction. Perhaps a 

 safe figure as regards the commercial value of manure 

 as it is likely to be handled on the average farm is about 

 $1.50 a ton. This approaches more nearly the price that a 

 market gardener, for example, may pay for such a product. 



This commercial evaluation must never become con- 

 fused with what is known as the agricultural value of a 

 manure. The former is based on composition, while 

 the latter arises from the effects as measured in crop 

 growth. A manure of high commercial value may, when 

 placed on the soil, yield only a low to medium agricultural 

 return. This latter evaluation is, of course, the one of 

 greatest significance in agricultural practice. A very 

 good example of this might be cited from the Ohio experi- 

 ments l with manure. In this case both treated and 

 untreated manures were evaluated commercially and 

 were then applied to the land. The value of the increased 

 crops in a three-years' rotation was then calculated in 

 terms of return to a ton of manure applied : 



COMMERCIAL AND AGRICULTURAL EVALUATION OF MANURES 



1 Thome, C. E., and others. The Maintenance of Fertility. 

 Ohio Agr. Exp. Sta., Bui. 183, pp. 206-209. 1907. 



