10 
The Colorado Experiment Station 
forms a temporary reservoir, holding the water for a time and 
then passing it on slowly to the more tight subsoil. 
Kind of Plowing for New or Old Land .—Plowing on old 
lands should be as deep as possible. If the plowing is done long 
enough before seeding to permit nature to do the settling and 
compacting, it can scarcely be too deep on silt and clay lands. If, 
however, breaking cannot be done a considerable period before 
seeding, it should be relatively shallow, because usually it can¬ 
not be properly settled and compacted immediately prior to seed¬ 
ing. The disk following the plow will be of service. But it does 
not equal time and rainfall. Besides, plowing breaks the exist¬ 
ing moisture relations and time is essential for readjustment. Un¬ 
less followed by rain, deep plowing immediately before seeding 
will give poorer yields than shallow plowing. 
Movement of Water in Soil .—After the water is caught by 
the soil, it undergoes certain movements. When it moves down¬ 
ward thru the spaces between the soil particles by its own weight, 
we say it percolates. When it crawls upward or downward or 
sidewise like water in a lump of sugar, or oil in a lamp wick, we 
say it is capillary or film movement, because it moves along as a 
thin film over the surface of the soil particles. Sometimes changes 
in temperature cause soil water to move. In that case we say 
there is temperature movement or thermal movement. 
Water is held in two ways in the soil, as a film which sur¬ 
rounds the soil particles and in the tiny spaces between soil par¬ 
ticles. When it rains, water enters the soil. When the surface 
gets more water than it can hold, it loses some by percolation to 
the soil below. That is, some of the free water flows from the 
soil spaces above to the soil spaces below. This process continues 
as long as it rains and often for a time afterwards, depending on 
the amount of rain. 
When percolation ceases, another movement begins. The films 
begin to crawl from particle to particle as water in a lump of 
sugar, only much slower. Very dry soils wet very slowly, but 
when the particles are very slightly moistened, they tend to draw 
water from the moister towards the drier soil particles. This 
movement continues until the pull away, is balanced by the pull 
to hold. 
Most deep soils in regions of moderate or slight rainfall 
never have their subsoils thoroly wet. In fact, they are rarely 
ever moistened beyond the depth of a few feet. The rains wet 
the surface. A portion of the water percolates a little further in. 
After percolation ceases, the water penetrates a little further by 
film movement. In such deep soils free water moving in the soil 
