COMMERCIAL FERTILIZERS 113 



QUESTIONS AND PROBLEMS 



1. What are the four high-grade nitrogenous commercial fertilizers, and 

 what is the per cent of nitrogen in each ? 



2. Name four important phosphatic fertilizers, the source from which 

 each is derived, and the condition under which each may be used to the 

 best advantage. 



3. Where is the greater part of potassium fertilizer obtained? What are 

 the probabilities of early exhaustion of the supply ? 



4. What is meant by complete fertilizer? What is meant by two-eight- 

 two or three-ten-five fertilizer ? 



5. Assuming that ground limestone costs $1.20 per ton delivered at 

 your railway station, and assuming that a farmer, at a cost of $4 per day, 

 can haul and scatter two loads of two tons each per day, what is the cost 

 of liming a twenty-acre field ? 



6. Estimating corn at 50 cents per bushel, how much increase in the 

 first corn crop would be required to pay the cost of the liming? 



7. What other benefits besides increase of the corn crop might result 

 from liming the soil ? 



8. Under what conditions may the use of commercial fertilizer be 

 continued indefinitely without injury to the soil? 



EXERCISES 



1. Study of fertilizers. Secure samples or descriptions of several 

 kinds of fertilizing materials and mixed fertilizers. Learn the approxi- 

 mate composition of each and the general appearance. Figure the 

 approximate market value of each after the manner indicated on 

 page 109. 



2. Effect of fertilizer upon plant growth. 



MATERIAL : Two one-gallon flower pots ; clean, washed sand ; a small 

 quantity of a complete fertilizer. 



Fill two one-gallon flower pots with clean, washed sand, and settle 

 by jarring until the sand is a half inch below the top of the pots. 



To one pot add 6 grams of a complete fertilizer containing from 2 to 

 3 per cent nitrogen, from 8 to 1 2 per cent available phosphoric acid, 

 and from 3 to 5 per cent potash, mixing thoroughly with the top four 

 inches of sand. The mixing is best done by removing the top four 

 inches of sand to a paper or oilcloth, mixing the fertilizer with it, and 



