194 Physics of the Soil. 



is out in the spring, so that the thawing and freezing will 

 tend to cover the seed and the thin mulch protect the 

 ground from too rapid drying until the young plants are 

 well rooted. 



The use of straw and other coarse litter and coarse sand 

 for mulching will generally only be practicable in gardens 

 and orchards and for the protection of shade trees arid 

 the like. 



227. Ridged* and Flat Cultivation It used to be a com- 

 mon practice to "lay by" the corn and potato crop with 

 a strong hilling of the rows. This practice, however, ex- 

 cept for potatoes, is now generally abandoned unless in 

 localities wher'e surface drainage is needed. The general 

 abandonment of the practice rests in part upon the be- 

 lief that the evaporation from the soil is appreciably in- 

 creased by this process on account of the greater amount 

 of surface exposed to the air. 



In making a practical test during the season of 1899 

 the results recorded in the following table were secured. 



These plots, each seven rows wide, alternated across a 

 field of nearly uniform soil and samples were taken under 

 and between every row. It will be seen that the soil re- 

 ceiving the flat cultivation contained at the end of the 

 growing season a little less water than the ridged plots, 

 which is contrary to the accepted belief. Since the ridges 

 are all shaded by the potato vines and since the wind cur- 

 rents niay be supposed to be less strong between the fur- 

 rows, perhaps this is as should be expected. It is true, 

 however, that the plots cultivated flat produced a little 

 larger yield per acre and on this account the soil should 

 have lost more moisture. It may be that the flat cul- 

 tivation did really make a larger saving of water and that 

 this saving was the cause of the larger yield. 



