Food for "The plus, -J-, and minus, , signs in the difference 



ants column, indicate the percentage more or less found by an- 

 alyses than was guaranteed. 



"There is a very close agreement between the calculated 

 and actual composition of these mixtures; the widest varia- 

 tion is 0.32 per cent, for Nitrogen, 0.76 per cent, for phos- 

 phoric acid, and 0.69 per cent, for potash. In home-made 

 mixtures the value of exactness in composition depends very 

 largely upon the value of the relative proportions of the plant 

 food applied to the soil for the different crops. A pound per 

 acre, more or less, of either Nitrogen, phosphoric acid, or 

 potash would probably not be observed in the results secured 

 from their use. Taking the widest variation in the above 

 mixture it would require 313 pounds to make a difference of 

 one pound in the Nitrogen, 133 pounds in the phosphoric 

 acid, and 145 pounds in the potash. The mixtures do con- 

 tain practically the amount and proportion of plant food that 

 they were intended to furnish, and, therefore, show that 

 farmers are able to make even mixtures of such raw materials 

 as the market afords. 



"A comparison of the commercial value per ton of the 

 materials used with that of an actual mixture also confirms the 

 results of analyses, the average difference between the two 

 values being but thirteen cents per ton. This is a severe test, 

 since in three cases out of the five the three forms of the ex- 

 pensive element Nitrogen were used, each of which has a dif- 

 ferent commercial value, and also because in three mixtures 

 ground bone or tankage was used, materials which in them- 

 selves are valued in a different manner than when they are 

 used in a mixed fertilizer. 



Valuation. 



"In Nos. 3960 and 4002 the cost of raw materials in- 

 cluded freight charges to point of consumption; in the others 

 the average cost of freight was $1.00 per ton. The cost of 

 mixing was variously estimated, ranging from 50 cents to 

 $1.50 per ton. In the table showing cost and value of the 

 mixtures $1.00 per ton has been assumed as the average cost 

 of mixing. 



