Irrigation Water as a Factor in the 
Dissemination of Weed Seed 
By G. E. EGGINTON and W. W. ROBBINS 
It is well known that there are many different agencies 
that are responsible for the spread of weed seeds. No other 
means of introducing weeds is probably so effective as the sale 
and distribution of impure commercial seeds. Weed seeds 
are also carried in screenings, in baled hay, in the packing 
about trees, in feed stuffs ; they are taken from place to place 
in the hair or wool or on the feet of live stock; they are con- 
veyed by birds. Light, winged seeds are often borne long 
distances by wind. In addition to the above means of seed 
dispersal, irrigation water is a most important factor in the 
dissemination of weed seeds in the irrigated sections of the 
western states. Ditch banks everywhere are densely over- 
grown with weeds, which shed their seeds in the water, and 
these are carried down stream, given a good soaking in transit, 
and planted on a well-soaked soil — all conditions being ideal 
for germination. In the belief that this was a prolific means 
of distributing weed seeds, an investigation was begun by this 
Station to determine the extent of distribution caused in this 
way. This investigation has just been completed and the re- 
sults are given herewith. 
It is believed that the data herein presented will serve to 
emphasize the fact that our irrigation waters are conveying 
tremendous quantities of weed seeds, that our ditch banks are 
more to be feared than our roadsides as sources of weed infes- 
tation, and that it will point to the need of regulations requir- 
ing the removal of weeds on ditch banks as well as along road- 
sides and show the value of grazing ditch banks for the con- 
trol of weeds upon them. 
Germination studies of weed seeds carried in irrigation 
waters are now under way. The results of these studies will 
be reported in a later bulletin of the Station. 
METHOD 
It was deemed advisable at the start to obtain data as to 
the actual quantities of seeds carried by typical irrigation 
ditches. For this purpose a cylindrical seed trap of fine copper 
wire gauze was constructed (Fig.l). It measures 10 inches 
