486 NATUKE AND PEOPERTIBS OF SOILS 



advantageously alter his fertilizer practice as tlie rotation 

 progresses and his soil changes in fertility. 



Such arguments do not always mean, however, that it pays 

 to buy the separate materials. As a matter of fact, in many 

 cases it does not pay, especially where only a small amount of 

 fertilizer is needed and it is impossible to cooperate with 

 other farmers. As a general rule, fertilizers should be bought 

 by the method that will give the greatest value for every dollar 

 expended, providing, of course, that the proper material is 

 purchased. Farmers can often avail themselves of the advan- 

 tage of both systems by asking for bids from various manu- 

 facturers on carload lots of mixed goods having a certain 

 composition. The farmers in this case designate the carriers 

 as well as the formula. All the advantages of machinery mix- 

 ing may thus be gained. 



274. How to mix fertilizers.^ — The first step in the buy- 

 ing of the separate fertilizer carriers is to obtain quotations 

 which should state the price a ton, the composition, and the 

 freight rate. "With this information, the most desirable car- 

 riers are selected and the amount of each is calculated.^ If 



* Certain materials should not be mixed, especially in large amounts. 

 Thus lime, especially the oxide and hydroxide forms or fertilizers carry- 

 ing lime in considerable amount, should not be mixed with ammonium 

 sulfate and animal manures, since ammonia is likely to be freed. Such 

 materials should be kept away from acid phosphate or the reversion of 

 the latter will occur. Calcium carbonate in small amounts, however, is 

 often mixed with fertilizers carrying acid phosphate. It is not wise to 

 allow moist acid phosphate to lie in contact with sodium nitrate, as nitric 

 acid may be liberated by free sulfuric acid. 



* Below are three satisfactory mixtures: 



2-12-0 



400 pounds of tankage. 

 100 pounds of sodium nitrate. 

 1500 pounds of acid phosphate (16%P205). 

 2-12-2 



320 pounds of tankage. 

 100 pounds of ammonium sulfate. 

 1500 pounds of acid phosphate (16%p20a). 

 80 pounds of potassium chloride. 



4-10-4: 



150 pounds of sodium nitrate. 

 100 pounds of ammonium sulfate. 



