EXTENSION COURSE IN SOILS. 53 
Determine the apparent average annual loss of this element from the soil during those 
years. 
7. One ton of clover hay contains approximately 5 pounds of phosphorus and timothy 
hay about 2\ pounds per ton. How many pounds of phosphorus are sold from the 
farm when a farmer sells 30 acres of clover averaging If tons per acre and 25 acres of 
timothy averaging 1\ tons of hay per acre? What is the value of this phosphorus at 
10 cents per pound? 
8. One ton of wheat bran contains about 25 pounds of phosphorus and cottonseed 
meal the same amount. How many pounds of phosphorus does a farmer bring to his 
farm when he buys 20 tons of bran, 8 tons of cottonseed meal, and 15 tons of clover hay? 
Is all of this phosphorus added to the soil? 
(a) The loss of phosphorus in the feeding transaction may be considered 20 per cent, 
the manure being hauled directly to the field. How many pounds of phosphorus will 
this farmer add to his soil through the purchase of these feeds? 
9. Twenty-five per cent phosphoric acid is equivalent to what per cent phosphorus 
(P)? Fifty pounds of the compound phosphoric acid (P 2 5 ) is equivalent to how 
many pounds of the element phosphorus (P)? 
10. One phosphorus fertilizer contains 14 per cent phosphorus, while another is 
marked to contain 30 per cent phosphoric acid. Which contains the more phos- 
phorus, and how much more? 
11. When rock phosphate containing 30 per cent phosphoric acid can be delivered 
for $8 a ton, what is the cost of 1 pound of phosphorus? 
12. When acid phosphate analyzing 16 per cent phosphoric acid can be had for 
$16 a ton, how many pounds of phosphorus can be purchased for a dollar? Compare 
this with rock phosphate. Which of these two fertilizers is soluble? 
13. The phosphorus contained in rock phosphate analyzing 13 per cent phosphorus 
and applied at the rate of 1,000 pounds per acre is sufficient to supply about how many 
75-bushel corn crops? 
14. How much basic slag analyzing 8 per cent phosphorus must be added per acre 
to return to the soil approximately the amount of phosphorus removed by three clover 
crops averaging 2 tons of hay per acre, two 75-bushel corn crops, and one crop of 
timothy hay averaging 1\ tons per acre? 
15. One thousand pounds of milk contains 0.8 of a pound of phosphorus. How 
much phosphorus is contained in the milk produced by one cow in a year if she aver- 
ages 30 pounds of milk per day? 
16. How many pounds of potassium are contained in a heavy clay loam analyzing 
2.5 per cent potassium? In a peat containing 0.5 per cent potassium? 
17. A poor, sandy soil analyzed 0.68 per cent potassium, while a peat analyzed 0.3 
per cent of this element. In comparing the percentages, what per cent more of 
potassium does the sand contain than the peat? 
18. In comparing the actual number of pounds in an acre 8 inches deep, what per 
cent more of potassium does the poor sand in problem 20 contain than the peat? 
Explain the different results obtained in these two problems. 
19. A 1,600-pound tobacco crop removes from 1 acre about 75.5 pounds of potas- 
sium. How many such crops will the potassium supply that is contained in an acre 
8 inches deep of a silt loam analyzing 2 per cent potassium? 
20. A 4-ton alfalfa crop removes from 1 acre about 95.5 pounds of potassium. What 
is the value of the potassium contained in 40 tons of alfalfa hay when 1 pound of this 
element is worth 6 cents per pound? 
21. Sixty-five pounds of potash (K 2 0) is equivalent to how many pounds of potas- 
sium? Fifty per cent potash is equivalent to how many per cent potassium? 
22. A man can buy muriate of potash analyzing 43 per cent potassium for $45 per 
ton and kainit containing 12 per cent potassium for $15 a ton. Both are soluble fer- 
tilizers. Which will give him the more potassium for his money? 
