No. 7. DEPARTMENT OF AGRICULTURE. 453 



retiu'iK d, is equivalent to but 2 per cent, of nitrogen, 20 per cent, of 

 phosphoric acid and less than 10 per cent, of the potash removed in 

 the crops mentioned. 



It seems to me, therefore, that the importance of the question 

 of the use of fertility constituents, is clearly established, and the 

 bearing of the composition and use of farm manures bears directly 

 upon this point, or upon the immediate and prospective fertility 

 of our soils. 



One difficulty encountered in the discussion of a subject of this 

 sort, is that we are dealing with a product that is extremely va- 

 riable. Farm manure is not uniform, either in its composition or in 

 reference to the organic matter contained in it, or in its proportion 

 of constituent elements. While variations in the original compo- 

 sition of the product occur and are due to kind of animal, age of 

 animal, use of animal, kind of feed, and amount of litter used, 

 though in any case it is worthy of our attention, because it does con- 

 tain those substances which are liable directly or indirectly to im- 

 prove our soils. 



Another point that is worthy of consideration in connection with 

 our study of farm manures is, that the constituents in them cannot 

 be compared with those contained in the various commercial sup- 

 plies, because associated with the nitrogen, phosphoric acid and 

 potash, in manures, there is more or less of organic vegetable mat- 

 ter, which has a very important modifying influence, both upon the 

 constituents in the soil^ to which it is applied, as well as to the con- 

 stituents contained in the manure itself. It very frequently hap- 

 pens, that the manurial effect of certain definite amounts of constit- 

 uents in a product of this sort, w^ould be greater than can be ac- 

 counted for by the effect of the constituents themselves, and from 

 this standpoint alone values are considerable, though because these 

 effects are again modified by kind of soil, kind of crop, kind of season, 

 etc., they are indefinite rather than definite amounts. 



In order, however, that we may have some definite proposition 

 to discuss, we must have either positive or assumed data in reference 

 to the yield of manure from an animal, and its composition. Expe- 

 riments conducted at the New Jersey Station, show that a cow of 

 1,000 pounds live-weight, well-fed, will produce, on the average, 12.8 

 tons of manure per year, and that the composition of this manure, 

 free from litter, averages : 



Nitrogen, . 457 per cent. 



Phosphoric acid, 0.300 per cent. 



Potash, 0.348 per cent. 



There are contained, therefore, in the product of each cow: 



Nitrogen, 117 lbs. 



Phosphoric acid, 77 lbs. 



Potash, 89 lbs. 



What this means in a large way, can be made clear by applying 

 the figures to the number of milk cows that are contained in any 

 one state. The State of Pennsylvania, for example, the statistics 

 show 1,055,071 cows. The constituents contained in the manure, 



