The Storage and Use of Soil Moisture 
79 
charged to the crop. The crop does not actually use all this 
water. Some of it is lost thru surface evaporation. Some is 
lost as run-off. Especially was this true in the case of winter 
wheat in 1912. When the heavy snows of that spring melted the 
soil was frozen below a depth of three inches. Xot only did 
we lose this moisture as run-off but the snow melted so fast that 
in some cases it washed off the unfrozen soil. 
The entire rainfall plus the water drawn from the soil is 
figured as total available water. Dividing the total number of 
pounds of water by the number of pounds of dry matter pro- 
duced, we have the number of pounds of water to produce one 
pound of dry matter. This table is not offered for its technical 
value. The method of procedure was too crude to give it much 
value from that standpoint. We are using it to prove what 
observation has so often indicated, that during unfavorable sea- 
sons a given amount of water will not produce as large a crop 
as during favorable seasons. An inch of water in a favorable 
season goes much further than a like amount in an unfavorable 
season. The table shows that some years almost twice as much 
water is required to produce a pound of dry matter as is re- 
quired in certain other years. The total rainfall alone is not 
sufficient to interpret results. The distribution of rainfall, evap- 
oration, temperature, relative humidity, and wind velocity, all 
affect the efficiency of the rainfall in crop production. The rain- 
fall of this section is seldom so low but that it would produce 
fair crops if properly distributed and accompanied by a favor- 
able rate of evaporation. The high rate of evaporation and the 
hot winds resultant from drouthy conditions are frequently more 
disastrous than the drouth itself. In a few days these will in- 
jure a crop to the point where it can at best only partially re- 
cover, whereas under more favorable conditions it would have 
held on for a considerable length of time and perhaps have been 
saved by a rain. This is often shown by results obtained from 
protected areas. 
The table also shows that a year which is favorable for small 
grain is not necessarily favorable for corn. An example of this 
is seen in 1908. The small grains did not use an excessive 
amount of water. Corn used more water than during any other 
year. Tn 1912 the small grains used a large amount of water 
and corn shows the best use of the available water of any year 
shown. 
