122 FERTILITY AND FERTILIZER HINTS 



Again, the crop to be raised may have a long growing season. 

 If such is the case it would not pay to use fertilizer whose plant 

 food is all in soluble forms. If the nitrogen is all soluble, as in 

 nitrate of soda and sulphate of ammonia, it may be used up or 

 lost before the crop has finished growing and some slower acting 

 form of nitrogen, as is contained in dried blood, cotton-seed 

 meal, tankage, etc., would no doubt give greater crop returns. 



The value of the crop must also be considered, for crops of 

 low market value cannot be expected to give profitable returns 

 with high priced fertilizers. The cost of a fertilizer of low 

 agricultural value may be greater than one that has a high value 

 in producing crops. Farm manures, wood ashes, land plaster, 

 etc., may be comparatively high in price for the amount of plant 

 food they contain or the good they do. 



Commercial Values. — The commercial value of a fertilizer is 

 entirely different from the agricultural value. It represents 

 the retail cost of raw materials of standard quality in the market, 

 from which the commercial or trade value of plant food may be 

 calculated. For example, nitrate of soda may be quoted at $50 

 a ton. This represents its commercial value. As nitrate of soda 

 contains 15.5 per cent, of nitrogen or 310 pounds of nitrogen in 

 a ton, its nitrogen has a commercial or trade value of a little 

 over 16 cents a pound. An acid phosphate containing 14 per 

 cent, of available phosphoric acid may carry a retail price of $14 

 a ton, which is its commercial value. The commercial or trade 

 value of the available phosphoric acid would be 5 cents a pound, 

 since 14 per cent, of available phosphoric acid is equal to 280 

 pounds of available phosphoric acid in a ton. Or an acid phos- 

 phate may be quoted at $1 per unit. This is its commercial value. 

 This means that the retail cost of 20 pounds of available phos- 

 phoric acid is $1. The commercial or trade value is then 5 cents, 

 a pound. The commercial or trade value does not mean that 

 nitrogen at 16 cents a pound will produce 16 cents worth of 

 crops, or available phosphoric acid at 5 cents a pound will pro- 

 duce crops that will bring 5 cents. These constituents may pro- 

 duce crops valued at more or less than 16 and 5 cents respectively, 

 depending upon many conditions as season, locality, kind or crop, 



