SOIL WATER 



77 



92. Other devices to prevent evaporation. — Plowing in the 

 early spring or immediately after taking off a crop of 

 small grain is a means of preventing evaporation. In regions 



e&capino moisture: 



3 1 f 1 



»l(SO Mpl 



NO MULCH 



Fig. 14. — The effect of a soil mulch is to break up the capillary spaces 

 within the mulch itself and thus to prevent the upward movement of water 

 through it. Water, therefore, remains in the lower soil instead of evaporat- 

 ing from the surface. This condition is shown in the right-hand column. 

 When no mulch is maintained the soil dries at the surface and then cracks, 

 which allows it to dry more rapidly below. 



in which grain crops suffer for moisture in the early spring, 

 it is not uncommon for farmers to harrow the small grain, 

 following the drill rows with a spike-tooth harrow with its 

 teeth turned backwards. This practice is likely to be very 

 beneficial. 



