78 



BULLETIN 355, U. S. DEPARTMENT OF AGEICULTURE. 



another portion produced 15.8 tons per acre. The rock phosphate cost $10 per ton 

 and the potash fertilizer $46. How many more dollars' worth of plant food in the 

 manure did it require to produce the gain in yield for that year? 



7. A mixture of acid phosphate and mmiate of potash in the proportion of 100 pounds 

 to 60 pounds, respectively, was applied to a field at the rate of 150 pounds per acre. The 

 field produced 14.5 tons of silage com per acre as compared with 3 tons where no treat- 

 ment was made. The acid phosphate cost this farmer §16 per ton, and the potash 

 fertilizer $45 per ton. ^Tiat was the cost of this fertilizer treatment, and what may 

 be considered the interest on the fertilizer investment for that year? 



A farmer owns a clay farm of 160 acres. For regular cropping purposes he has six 

 20-acre fields. His crops are alfalfa, corn (two fields each year), oats, wheat, and red 

 clover. The alfalfa occupies a field for five years, then is plowed for corn. The crops 

 on the other fields are, in the order named, corn, oats, wheat, red clover. Rye, or rj-e 

 and vetch, are used as a cover crop following the crops of com. The crops are so 

 planned in the five fields not gi'owing alfalfa that each year the farmer has two fields 

 of corn and one field each of oats, wheat, and clover. The analysis of the soil on this 

 farm is fairly uniform and shows per acre in the total 8 inches of surface 4,000 pounds 

 of nitrogen, 2,000 pounds of phosphorus, and 24,000 pounds of total potassium. 



8. If C stand for com, for oats, W for wheat, and CL for red clover, and A for 

 ahalfa, fill in the blank below so that the order of cropping in each field will be as given 

 above, and so that there will be for harv'est each year one field of alfalfa, two of com, 

 and one each of oats, wheat, and clover. 





Field. 



Year. 



1 



2 



3 



4 



5 



6 



1 



A 













2 



A 













3 



A 













4 



A 













5 



A 











1 



9. Assuming that the plant food liberated from this soil during the average season 

 is equivalent to 2 per cent of the total nitrogen, 1 per cent of the phosphorus and \ of 

 1 per cent of the potassium : 



(a) From table 23, reference Xo. 5, page 154, determine whether sufficient of the 

 plant-food elements, nitrogen, phosphorus, and potassium, would be liberated during 

 a growing season on this farm to produce a 100-bushel crop of corn. 



(b) Compute whether any of these plant-food elements is present in this soil in 

 BuflBcient quantity to produce the maximum of any crop noted in table 23. 



] 0. The yields of crops on the farm averages 4 tons of alfalfa hay per acre, 50 bushela 

 of com per acre with 2 tons of stover, 50 bushels of oats T\ith 1^ tons of straw, 25 

 bushels of wheat ^vith 1^ tons of straw, and 3 bushels of cloA-er seed per acre with 

 li tons of clover hay the first cutting, three-fourths tons clo^-er straw fi'om hulling, 

 and one-half ton gro^i:h of clover to turn under for corn. 



(a) If the farmer sells his alfalfa, the grain including the corn, and the clover seed, 

 but retmns to the soil all corn stover, straw, and clover; and if each ton of clover 

 fixes in its growth 40 pounds of nitrogen, and each clover crop fixes 12 pounds of 



