Properties of Colorado Wheat 7 
RELATION OF WATER SUPPLY TO YIELD 
1 his brings up possibly the most important practical question 
that we have to deal with in wheat growing, namely: What is 
the relation of the water supply to the yield and character of 
our wheat? The answer to this question is somewhat difficult to 
present, but for the sake of having a definite presentation of our 
answer we will assume that water has two sharply distinguishable 
effects, direct and indirect, and that these may vary with the 
manner of application. If we should have a long continued rain¬ 
fall which actually changed the chemical composition of the whole 
plant and its product, the seed, we would consider it a direct 
effect. Such an effect is possible, but if the rain or moist spell 
chanced to come during a period of hot weather, with little wind, 
and the rust developed, as we know it will in Colorado, we would 
consider this an indirect effect of the wet and warm weather. 
IRRIGATION AFTER WHEAT IS IN HEAD DOES NO 
GOOD 
1 hese different effects are actually produced and we cannot 
control these conditions. So far as the growers of wheat in Colo¬ 
rado are concerned, it would be a good thing if we had no rain 
at all from the time the wheat comes into head till after it is 
threshed, for water, applied after the wheat comes into full head, 
does no good and may be very dangerous, especially in the form 
of frequent light rains accompanied by warm, cloudy weather. 
It is perfectly well understood that plants must have water 
in order to grow, and while some plants may thrive in a compara¬ 
tively dry soil and climate, as the wheat plant is said to do, there 
is a period during which an amply sufficient supply is necessary 
for its best development and no abundance of supply, at some 
other time, will make up for a lack during this period; for this 
reason this is often spoken of as the critical period. 
We did not attempt in our work to establish the limits of this 
period. Every man who has cultivated plants has learned that it 
is a general rule that plants which have been stunted, whatever 
the cause, will not produce as good plants as those that have been 
kept continuously in good growing condition, even though the 
cause of stunting may be wholly removed, as in the breaking of 
droughty conditions; a few varieties of plants may recover from 
such stunting, but most plants will not. The wheat plant needs 
an abundant, i.e., an amply sufficient, supply of moisture to keep 
it growing vigorously till it is well advanced in boot. If there 
should be any signs of a want of moisture previous to this time, 
it should be irrigated. If, however, there is no lack of moisture 
