A Study of Colorado Wheat 
7 
is such that the addition of considerable quantities of this element, up 
to 6o pounds of soluble phosphorus per acre, produces no perceptible 
effect upon the crop, it will be appreciated, that the formation of 
quantities of nitrates corresponding to the amounts of .nitric-nitrogen 
given above, or even the less amounts indicated by our general sam¬ 
ples, may produce a very pronounced influence upon the character and 
properties of the wheat produced. 
In order to find out what effects we were to expect from the pre¬ 
dominance of one or other of the three elements usually considered 
in this connection, nitrogen, phosphorus and potassium, but particu¬ 
larly of nitrogen, we applied these singty in different quantities, aim¬ 
ing to have a very excessive quantity in at least one case in each series 
of experiments. To these three elements of plant food we added 
water, because the supply of this is usually under our control in Colo¬ 
rado and our opportunity for studying its effects is better than that 
enjoyed by many other experimenters. 
APPLICATION OF WATER A PHYSIOLOGICAL PROBLEM 
I will digress to state what seems self evident, i.e., that the 
question of an advantageous or indispensable water supply to the 
wheat plant, for instance, is rather a physiological than an engineer¬ 
ing question, though it is generally considered from the latter stand¬ 
point. It is not only a question of how much or little water is actually 
needed, but also a question of the time and manner of application. To 
be more specific, I believe that the application of one acre^foot of 
water at the proper time may produce just as favorable results as the 
same amount differently distributed in regard to time. Further, i 
foot, or even less, of water, applied at the proper time may produce just 
as good results as 2 or even 3 feet, provided that the supply at the prop¬ 
er time in the development of the plant be adequate to its needs; after 
this the water supplied is of little or no benefit, and produces but little 
rr no effect upon the composition of the plant or grain. Two feet of 
water applied to the soil as irrigating water, even if it be distributed at 
intervals of a few days, eight to ten days, may do neither the plants nor 
the grain any harm, and produce no perceptible difference in the compo¬ 
sition of either. Whereas, the same amount of water falling in a series 
of light rains would certainly prove detrimental, perhaps disastrous, 
even though the last ten, or possibly even fifteen days before harvest 
were fair and dry. A comparison of the composition of the plant, as in¬ 
dicated by the various forms of nitrogen and the ash constituents given 
for the crop of 1913, in Bulletin 208, with that for 1915 in Bulletin 217, 
in which years the plants received essentially the same amounts of water^ 
will show how great a difference the manner of application may make. 
In 1913, the crop received 12 inches as irrigating water and 6.77 inches 
rainfall; in 1915, it received 13 inches of rainfall and 6 inches of irri¬ 
gating water. The plants in 1915 contained less nitrogen and srhallet 
