SHADING AND EVAPORATION 151 
tions, it was found that shading a pot of soil, which 
otherwise was ‘subjected to water-dissipating influ- 
ences, saved 29 per cent of the loss due to evaporation 
from a pot which was not shaded. This principle 
cannot be applied very greatly in practice, but it 
Fic. 34. Alfalfa in cultivated rows. This practice is employed to make 
possible the growth of alfalfa and other perennial crops on arid lands 
without irrigation. 
points to a somewhat thick planting, proportioned 
to the water held by the soil. It also shows a pos- 
sible benefit to be derived from the high header 
straw which is allowed to stand for several weeks 
in dry-farm sections where the harvest comes 
early and the fall plowing is done late, as in the 
mountain states. The high header stubble shades 
the ground very thoroughly. Thus the stubble 
may be made to conserve the soil-moisture in dry- 
