Thorough Tillage: Syste:m lor Plains or Colorado. 21 
face, checking this seriously rapid evaporation. Of course the 
finer the mulch the more perfect its action. Were it not for the winds 
on our plains, we could make a dust mulch and thus get the most 
perfect earth mulch for checking evaporation of moisture from the 
soil. The danger from wind blowing soil and seed from the field 
is too great and farmers are cautioned not to make the earth mulch 
too due. Leave the soil as loose as possible on top, so as to prevent 
this capillary action reaching to the surface, but do not make it 
of dust-like fineness. 
The blanket-like action of this earth mulch and the difficulty 
the water has in getting through it, is well illustrated by loaf sugar 
and granulated sugar. Place one of these hard squares of loaf 
sugar in a teaspoon and lower it so it is partly submerged in a 
cup of coffee. How soon it is saturated. Place the same amount 
of granulated sugar in the teaspoon and lower as before in the 
coffee and observe how much longer it takes to saturate the finely 
ground sugar than it did the loaf sugar. The finer flour sugar 
used by confectioners takes still longer for water to saturate it. A 
thoroughly fine, dry, dust blanket requires more moisture to wet 
through it, to the soil you want to reach with moisture, since the 
dust is so much finer and has therefore a greater film surface than 
the under soil. On the other hand, when moisture seeks to come 
up, it has the same difficulty to get to the surface of the dust blanket 
and be lost in the hot, dry air above, which it experiences in getting 
down. 
For this reason our earth mulch should be kept as fine as the 
action of prevailing winds will permit. 
Remember, capillary force will carry down as well as up, and 
we can deepen the root growing power of our farm crops by deep 
plowing and summer culture, which stores and conserves soil 
moisture. 
V. EXPERIMENTS AND EXPERIENCE IN SEMI-ARID 
FARMING IN OTHER STATES. 
The following questions were sent to the experiment stations 
in each of the western states in the semi-arid regions, where crops 
are being grown without irrigation. 
QUESTIONS. 
1. To what extent is semi-arid farming - , without irrigation, practiced 
in your State. 
2. With what success? 
3. Do your best farmers under this system of farming try to obtain 
a crop each year from a given field, or only every other year? 
4. Will you tell me what preparation you think makes the most sat¬ 
isfactory seed bed for semi-arid farming conditions? 
5. What is your average rainfall in localities where semi-arid farm¬ 
ing is practiced? 
