362 SOIL PHYSICS AND MANAGEMENT 



cult to move than the individual particles. The more important 

 effect of limestone, however, lies in its power of correcting acidity, 

 rendering the soil more favorable for the growth of legumes which 

 furnish organic matter and nitrogen (Fig. 175), also for soil-bind- 

 ing crops, such as timothy and bluegrass. 



2. Protection by Crops. The surface of rolling land should 

 be kept covered with soil-binding crops as much of the time as 

 possible. For this purpose meadows, pastures and catch and cover 

 crops are indispensable in the farming of rolling lands. 



(a) Meadows and Pastures. The perennial grasses, timothy in 

 the northern states and red top and Bermuda grass further south j on 

 acid soils are good meadow grasses. Bermuda grass makes good 

 pasture and, if cut early enough, fairly good hay. Its growth is 

 such as to stop washing very well. It is more profitable to grow one 

 or more legumes with the grasses, as the latter use nitrogen fixed 

 by the legume. This is particularly desirable on those soils deficient 

 in nitrogen. Together these plants form a good sod, which protects 

 the surface and holds the soil together. 



Much of these hilly lands should never be plowed, but kept in 

 pasture. Blue grass, timothy, red top and other grasses, together 

 with red, alsike and white clover, sweet clover (Melilotus alba), and 

 Japan clover (Lespedeza striata), may be seeded in addition to 

 native grasses that follow upon the removal of the forest. One or 

 more of these should be able to get a good foothold regardless of 

 whether the soil is acid or contains Jimestone. These legumes 

 enable the grasses to make a much better sod. As already pointed 

 out, legumes in general require a soil containing limestone for good 

 growth. Japan clover, however, seems to be indifferent. Sweet 

 clover is more successful than any of the other clovers under very 

 unfavorable conditions if its two requirements rthorough inocula- 

 tion and abundance of limestone are satisfied. It makes a strong 

 growth and may be pastured or grown for hay and seed. Blue grass 

 soon starts in it, living in part on nitrogen fixed by the legumes. 

 This increases the amount of pasture afforded and forms a better 

 protection for the soil. 



(b) Catch and Cover Crops. Cultivated land should not be 

 left unprotected throughout the winter and spring months, especially 

 in those sections where the soil is not frozen during any consider- 

 able part of the winter. Cowpeas or soybeans may be seeded be- 

 tween the rows of corn at the last cultivation or between the trees 

 in orchards. Hairy or winter vetch and Japan clover are more 



