6 
Research Bulletin No. 5 
field under field conditions and has been subject to the same 
detrimental or favorable factors that are common to all fields 
under like conditions. 
It is not our aim in offering this work to teach actual farm 
practices affecting crop production, but to discuss underlying 
principles and show the effect of certain conditions. The ap- 
plication of these principles to the farm practices must be left 
to the farmer. We can show that a certain surface condition is 
more efficient than some other condition in catching water from 
rains. We also show that weeds use the water. It is left to the 
farmer to apply the principles. He may stack his grain and plow 
his stubble ground, or he may use the disk after the binder. If 
he can kill the weeds and get the surface in condition to hold 
moisture by either method, he has applied the principle. Local 
conditions on the farms vary so much with locality that it would 
indeed be hard to discuss the practices. In one section the 
problem would be to increase the yields of grain for the market 
and in another it would be to get feed for live stock. In order to 
bring farm practices up to the point of greatest efficiency, it is 
essential that the farmer understand the conditions under which 
he is farming and the principles affecting the practices. A thoro 
knowledge of the prevailing weather conditions, soil conditions, 
and nature and requirement of crops is essential. He can then 
work out the most economical practices. 
From the standpoint of storing moisture in the soil, we have 
found summer tilling, which is clean cultivation without any 
crop for a season, the most ideal way in which to store moisture. 
When the rainfall of a season is insufficient to produce a prof- 
itable crop, it may be better to summer till than crop every year 
and thereby store a small portion of one season's rainfall to use 
with the rainfall of the following season for the production of a 
single crop. In other words, "to use not two years' rainfall for 
one crop," but rather a small portion of the first year's rainfall, 
added to a somewhat larger portion of the second year's rainfall 
for the crop. Our investigation shows that it is only under 
favorable conditions that as much as 33 per cent of the rainfall 
of one season can be carried over to the next, and that during 
the most unfavorable season only 10 per cent was carried over. 
Probably not more than 60 per cent of the second year's rainfall 
is utilized by the growing crop, and it is probably safe to assume 
that considerably less than one year's rainfall is fully utilized 
for crop production under the best system of summer tillage. 
Summer tilling is a system that has been practiced for a long 
