COMMERCIAL FERTILIZERS 43 



40 pounds of nitrogen. Since nitrate of soda contains 16 per cent 

 nitrogen, one pound of nitrate of soda will contain .16 of a pound of 

 nitrogen (i X .16 = .16). Therefore as many pounds of nitrate of soda 

 will be required to furnish 40 pounds of nitrogen as .16 is contained in 

 40 (40 -r- .16 = 250), or 250 pounds. 



Similar calculations can be made of phosphoric acid and of potash 

 by substituting 14 per cent for phosphoric acid and 50 per cent for potash. 



Suppose a ton of a 4-8-3 fertilizer is to be made, how much nitrate 

 of soda, acid phosphate, and muriate of potash will be needed? First, 

 find the number of pounds of nitrogen, phosphoric acid, and potash in 

 a ton of a 4-8-3 fertilizer: 



2000 X .04 = 80, or 80 pounds of nitrogen. 



2000 X .08 = 1 60, or 1 60 pounds of phosphoric acid. 



2000 X -03 = 60, or 60 pounds of potash. 



Next, find the amounts of nitrate of soda, acid phosphate, and muriate 

 of potash necessary to furnish the required number of pounds of nitrogen, 

 phosphoric acid, and potash: 



80 -i- .16 = 500, or 500 pounds of nitrate of soda needed to furnish 

 80 pounds of nitrogen. 



i6o-f- .14= 1142.8, or 1142.8 pounds of acid phosphate needed to 

 furnish 160 pounds of phosphoric acid. 



60 -f- .50 = 120, or 120 pounds of muriate of potash needed to furnish 

 60 pounds of potash. 



The cost of such a mixture may be easily found by multi- 

 plying the calculated amount of each ingredient by its average 

 market price per pound, and finding the sum of the products. 



When buying the ingredients for home mixing, better 

 rates may be obtained by buying in car-load lots. The 

 saving is not only on the original cost but also in the reduction 

 of freight charges. 



SOIL AMENDMENTS 



What a soil amendment is. Certain substances are often 

 added to the soil for the purpose of improving it physically 



