DRAINAGE 53 



8. If a crop of potatoes following a clover crop requires 

 a special fertilizer, 0-8-7, instead of a 28-7, using the pre- 

 ceding data for the cost of material, estimate the saving on 

 5 tons of special fertilizer. 



9. What is the difference in the cost of a 4-8-4 and a 

 0-8-4 fertilizer ? 



DRAINAGE 



63. Low and wet land not suitable for farming can usu- 

 ally be made into rich and productive fields by a proper 

 system of drainage. 



EXERCISE 



1. A fall of 6 in. for each hundred feet is considered a good 

 grade for farm drainage. How much fall is this to the rod ? 



2. A fall of 3 in. for each hundred feet is considered a 

 minimum grade for farm drainage. How much fall is this 

 to the rod ? 



3. A 40-acre field in the form of a square is 5 ft. higher at 

 one end than at the other. How much fall is this to the rod ? 



4. If 4-inch tiling 1 ft. long costs $20 per 1000, and the 

 cost to dig the ditch, lay the tile, and fill the ditch is 250 

 per rod, what will it cost to tile a field 40 rd. by 80 rd., if 

 the tiles are run in strings lengthwise of the field and 

 placed 4 rd. apart, the outside ones being 2 rd. from either 

 side ? How much is this per acre ? 



5. With wheat at $1 per bushel, what must be the in- 

 crease in yield per acre to make it possible to pay half the 

 expense of tiling the land in 2 years' time ? 



6. With corn at 400 per bushel, what must be the increase 

 in yield per acre to make it possible to pay the remaining 

 expense of tiling the land in 2 yr. more ? 



7. What per cent did the farmer make on the expense of 

 the tiling ? 



