222 NATURE AND PROPERTIES OF SOILS 



itself being of minor importance. Similarly percolation loss 

 is important because of the nutrients carried away, rather 

 than because of the waste of the water. Since a certain 

 amount of percolation must take place and because a water- 

 logged soil is unsanitary for plants, rapid drainage is essen- 

 tial. Of the various methods available, tile drainage is the 

 most satisfactory. Evaporation loss, as with run-off and per- 

 colation, can be but very slightly checked. The soil-mulch is 

 important in that the cultivation necessary to produce it keeps 

 down the weeds and in this manner it eliminates serious crop 

 competition for nutrients and moisture. 



