EFFECT OF TIME OF IRRIGATION ON KERNEL DEVEL¬ 
OPMENT OF BARLEY 
By Harry V. Harlan, Agronomist in Charge of Barley Investigations, and Stephen 
Anthony, formerly Assistant, Office of Cereal Investigations, Bureau of Plant Industry, 
United States Department of Agriculture 
The studies of kernel development of barley made at Aberdeen, Idaho, 1 
in 1915 and 1916, and previously reported, 2 gave such satisfactory results 
that in 1917 an attempt was made to use this method of inquiry in a 
study of the effect of irrigation water. It is the common practice in 
irrigated districts so to arrange the applications of water that the last 
irrigation is given a considerable time before maturity, usually shortly 
after flowering. This, of course, is to prevent lodging, for as the weight 
of the grain increases, the chances of lodging are increased. There is 
also a widespread belief that during the later stages of ripening little 
absorption from the soil solution takes place and that the final matura¬ 
tion of the kernel can take place in the shock as well as before cutting. 
This latter belief was not substantiated in the work of 1915 and 1916, 
but there seemed to be no definite information as to how late in its 
growth period the plant could use water or just what occurred when 
a plant suffered from lack of water. 
Although it was hoped that some information could be gained on the 
general response to applications of water, the effect of delayed irrigation 
was made the primary object of the experiment. The factors affected by 
irrigation are so numerous and so involved that the final statement of 
yield per acre does not afford much basis for interpretation. While the 
method used may not show any direct relation to yield, it does show 
the effect on kernel development. The development of the individual 
kernels is one of the three factors of yield, the other two being the number 
of kernels per spike and the number of spikes per unit area. The period 
during which the quantity of water or the application of water affects 
the size of the kernel is worth determining. Knowledge of the period 
during which the application of water affects the growth or maturation 
of the plant affords a basis for the better understanding of irrigation. 
1 These studies were made on the Aberdeen Substation, Aberdeen, Idaho, in connection with cereal 
experiments conducted cooperatively by the Idaho Agricultural Experiment Station and the Office of 
Cereal Investigations, Bureau of Plant Industry, United States Department of Agriculture. 
* Harlan, Harry V. daily development of kernels of hannchen barley from flowering to 
maturity at Aberdeen, Idaho. In Jour. Agr. Research, v. 19, no. 9, p. 393-430, 17 fig., pi. 83-91. Liter¬ 
ature cited, p. 429. 1920. 
-and Anthony, Stephen, development of barley kernels in normal and clipped spikes 
and the limitations of awnless and hooded varieties. In Jour. Agr. Research, v. 19. no. 9. p. 431-472, 
13 fig. 1920. 
Journal of Agricultural Research, 
Washington, D. C. 
xg 
Vol. XXI. No. 1 
Apr. 1, 1921 
Key No. O221 
(29) 
