TILLING THE SOIL 61 



4. How many times as much available plant food 

 Jn soil cultivated to the depth of 6 in. as in soil culti- 

 vated only 4 in. deep ? 



5. If a man and team can plow i l /2 acres 6 in. 

 deep, or 2 acres 4 in. deep, in a day, how much more 

 does it cost per acre to plow land 6 in. deep than to 

 plow it only 4 in. deep ? Labor worth $2.40 per day. 



6. If a man and team can till 3 acres thoroughly 

 in a day, or 5 acres in a careless manner, how much 

 more per acre does a good job cost, labor being worth 

 $2.40 per day? 



7. How much more per acre does it cost to both 

 plow and till well? How many additional bushels of 

 oats worth $0.36 per bu. will it take to pay for the 

 additional labor? 



8. How much will be the gain if but 40 bu. of oats 

 can be raised with shallow plowing and careless seed- 

 ing, and 57 bu. with the extra work? How much will 

 these oats be worth at 24 cents per bu. ? At $0.30 per 

 bu. ? At the present price of oats ? 



9. A certain piece of land yields 35 bu. of corn 

 per acre. By careful cultivation the farmer is able to 

 increase this yield to 60 bu. With corn worth $0.40 

 per bu. how many additional days' labor at $i per day 

 will the extra yield pay for? 



10. If he spends but 20 days' extra time on his 

 i2-acre field of corn to produce the increase in crop 

 shown in problem 9, how much does he get per day for 

 his extra time? 



1 1 . Suppose a farmer is able to double the average 



