104 AGRICULTURE 



In one' ton Plant-food needed 



Nitrogen 1.65 Ibs. per cwt. x 20 cwt. a 33 Ibs. 

 Available phos- 

 phoric acid 10 Ibs. per cwt. x 20 cwt. = 200 Ibs. 

 Potash 2 Ibs. per cwt. x 20 cwt. = 40 Ibs. 



First find how much cotton-seed meal is needed to afford 33 pounds 

 of nitrogen. The table on page 106 gives the per cer* of nitrogen in 

 cotton-seed meal as 6 ; this means that each hundredweight of meal 

 contains 6 Ib. of nitrogen. Evidently to supply 33 Ib. of nitrogen, as 

 many hundredweight of meal are needed as 6| is contained times in 33. 

 Thus 33 -f- 6| = 5.07 cwt., or 507 Ibs., of cotton-seed meal are needed. 



Next find how much phosphoric acid and potash this amount of meal 

 will supply. From the tables below it is seen that I cwt. of cotton-seed 

 meal contains 2.8 Ibs. of phosphoric acid ; therefore, 5.07 cwt. contain 

 (5.07 x 2.8) 14.196 Ibs. Likewise for potash, 5.07 cwt. cotton-seed 

 meal contain .07 x 1.8 = 10.126 Ibs. of potash. 



Lbs. phosphoric acid needed 200 



Less Ibs. phosphoric acid supplied in 507 Ibs. c.-s. meal 14.2 



Lbs. phosphoric acid to be supplied in phosphate 185.8 



How many pounds of phosphate containing 16% of available phos- 

 phoric acid are needed to furnish 185.8 Ibs. of phosphoric acid? Evi- 

 dently as many hundred as 16 is contained times in 185.8. Thus, 

 185.8 -4- 16 = 11.61 cwt., or 1161 Ibs. of acid phosphate are required. 



Calculate how many pounds of kainit to use. 



Lbs. potash needed 40 



Less Ibs. potash in 507 Ibs. c.-s. meal 10.2 



Lbs. potash to be supplied in kainit 29.8 



To furnish 29.8 Ibs. of kainit requires as many hundredweight of 

 kainit as 12 (the number of pounds of potash which the table shows is 

 contained in i cwt. of kainit) is contained times in 29.8. Thus 29.8 -r- 12 = 

 2.46 cwt., or 246 Ibs. of kainit are needed. 



Combining these three results : 



507 Ibs. cotton-seed meal "1 fnitrogen 33 



1161 Ibs. acid phosphate (16%) I contain Jav. phos. acid 200 



246 Ibs. kainit [potash 40 



