WATER OF GRAVITATION IN THE SOIL 105 
The gravitational soil-water cannot long remain 
in that condition; for, necessarily, the pull of gravity 
moves it downward through the soil pores and if 
conditions are favorable, it finally reaches the stand- 
ing water-table, whence it is carried to the great 
rivers, and finally to the ocean. In humid soils, 
under a large precipitation, gravitational water moves 
down to the standing water-table after every rain. 
In dry-farm soils the gravitational water seldom 
reaches the standing water-table; for, as it moves 
downward, it wets the soil grains and remains in the 
capillary condition as a thin film around the soil 
grains. 
To the dry-farmer, the full water capacity is of 
importance only as it pertains to the upper foot of 
soil. If, by proper plowing and cultivation, the 
upper soil be loose and porous, the precipitation is 
allowed to soak quickly into the soil, away from the 
action of the wind and sun. From this temporary 
reservoir, the water, in obedience to the pull of 
gravity, will move slowly downward to the greater 
soil depths, where it will be stored permanently 
until needed by plants. It is for this reason that 
dry-farmers find it profitable to plow in the fall, as 
soon as possible after harvesting. In fact, Camp- 
bell advocates that the harvester be followed im- 
mediately by the disk, later to be followed by the 
plow. The essential thing is to keep the topsoil 
open and receptive to a rain. 
