106 The Sweet Potato 



by the convenience and availability of the possible 

 materials virbich will supply the desired plant-food. 



For the northern commercial sections, Miller^ rec- 

 ommends " a fertilizer analyzing 2 to 4 per cent of 

 nitrogen, 8 per cent phosphoric acid and, vphen avail- 

 able, 8 to 10 per cent of potash." Assuming that cot- 

 ton-seed meal is the most convenient source of organic 

 nitrogen (vyhich is preferred to inorganic forms for 

 sweets), and acid phosphate and sulfate of potash the 

 best carriers of phosphoric acid and potash respectively, 

 the following fertilizer may be mixed : 



Composition of fertilizers, 4 per cent nitrogen, 8 per cent 

 phosphoric acid and 10 per cent potash.: 



(1) Use cotton-seed meal containing 6.5 per 

 cent of nitrogen. 



(2) Use acid phosphate containing 16 per cent 

 phosphoric acid. 



(3) Use sulfate of potash containing] 46 per cent 

 potash. 



(4) 20 Cwt. (in one ton) X 2 per cent N = 

 40 lb. nitrogen -h- 6.5 (nitrogen) in c. s. meal 



= 615 lbs. c. s. meal 615 lbs. 



(5) 20 Cwt. (in one ton) X 8 per cent phos- 

 phoric = 160 lbs. phosphorous -i- 16 (phos- 

 phoric in acid phosphate) = 1000 lbs. 



acid phosphate 1000 lbs. 



(6) ^0 Cwt. (in one ton) X 10 per cent K. 20 

 = 200 lbs. potash h- 50 (potash in sulfate 



of potash) = 400 lbs. sulfate potash 400 lbs. 



2015 lbs. 

 By calculating the cost of such, a fertilizer with local 



1 Farmers' Bull. 999. 



