EXTENSION COURSE IN SOILS. 77 
in them and do not come in contact with a sufficient amount of the 
soil to supply their needs. This is particularly true when fine- 
rooted crops are to be grown. The use of heavy rollers to firm such 
soil results in great improvement in this respect. Not only does the 
rolling and firming of the soil have the effect of bringing the roots in 
direct contact with a much larger area of soil surface, but it permits 
a more rapid conduction of the heat from the surface downward. 
In this way the lower layers of the soil are warmed, and this greatly 
increases the growth of the roots and promotes bacterial changes, 
such as nitrification, to which the fertility of the soil is in part due. 
Crops for marsh soils. — A great variety of crops have been grown 
on marsh soils on account of their large supply of nitrogen. They are 
especially adapted to crops which produce rank growth and require 
large quantities of this element, such as corn, cabbage, rape, turnips, 
beets, and potatoes, though, of course, the quality of sugar beets and 
potatoes grown on such land may not be quite so good as when 
grown on upland soil. Since marsh soils as a whole are apt to be cold 
and affected by local frosts, care should be taken in the selection of 
crops, especially in northern climates. Here corn and potatoes, for 
example, might be out of the question. On the other hand, cabbage, 
rape, turnips, hay, of which a mixture of timothy and alsike clover 
is perhaps the best, and grain to a limited extent when proper care is 
taken may be grown to advantage. 
EXERCISES, LESSON X. 
PROBLEMS. 
1. A man had 40 acres of marsh land which produced on an average 1 ton of wild 
grass per acre, valued at about $3 per ton. He spent $1,000 in draining it. Now 
those 40 acres raise corn averaging 15 tons of silage corn per acre, valued at at least $3 
per ton. Determine this man's interest on his investment. 
2. Fifteen tons of manure per acre were applied on a drained peat soil. How many 
pounds of phosphorus and potassium were applied? How big a crop of corn will this 
amount of potassium supply? 
3. Two hundred pounds per acre of muriate of potash were applied to a muck soil. 
What was the cost of this application at $46 per ton, and how many pounds of potassium 
per acre were applied? (See table 24, p. 157, Ref. No. 5.) 
4. Compare the value of the manure applied in problem 2 with the cost of the potash 
fertilizer in problem 3. 
5. A portion of a peat marsh was treated with manure at the rate of 15 tons per acre; 
another portion was treated with an application of 400 pounds of muriate of potash per 
acre, costing $47 per ton. The first year the manured portion produced 10.5 tons of 
silage (green) corn per acre, and the second year a yield of 6 tons was secured with- 
out any further treatment. On the potash portion the corn averaged 14 tons the first 
year and 14 tons the second year, without further treatment. Compare the results pro- 
duced with the cost of manure and fertilizer in this case. 
6. On another marsh (muck), an application of a mixture of muriate of potash at the 
rate of 200 pounds per acre and rock phosphate at the rate of 800 pounds per acre pro- 
duced 12.5 tons of silage corn per acre. An application of 25 tons of manure on 
