4 
Colorado Agricultural Experiment Station 
true of our cultivated flowering plants, but our field crops will act in 
the same way if handled in the same manner. For instance, the potato, 
which has been grown for tubers almost indefinitely, produces varieties 
that fail to set seed balls, which are the true seed of the potato. We 
have varieties of alfalfa that are non-seed-producing. In fact, many 
plants have been found in our investigations that even fail to produce 
flowers, simply forming a modified growth without the functional or¬ 
gans of reproduction where the flowers should develop. Of course 
such variations disappear sooner or later unless propagated by vege¬ 
tative cuttings. Since alfalfa is commercially propagated by seed, 
sterile plants do not originate seedless varieties. Only seed bearing 
plants are propagated. 
Influence of Moisture Supply .—It is the common experience of 
every farmer who grows alfalfa, that the conditions which make for the 
best yields of hay, are not conducive to seed production. The heaviest 
yields of seed have been secured where the plants have seemed to make 
a rather dwarfed growth, due to the lack of moisture or some other con¬ 
dition adverse to the rapid development of forage. These plants evi¬ 
dently had sufficient moisture at the right time to set and fill the seed, 
for without any moisture the seed will “blast” and fail to fill. If too 
much water is applied the seed fails to set apparently due to the lux¬ 
uriant growth of forage that follows. It seems fair to conclude that the 
regulation of moisture at the right time and in the right amount is one 
of the important factors that influences the production of alfalfa seed. 
It seems almost impossible to formulate a rule to fit all conditions of 
farms, subsoils and seasons. In one case, three to four irrgations were 
found necessary to produce seed on a field of heavy adobe that would 
not absorb moisture easily. While on a lighter loamy soil, one irriga¬ 
tion would induce so rank a growth of hay that the crop was a failure. 
Climatic Conditions and Other Influences .—Aside from the in¬ 
fluence of vegetative growth and the moisture supply, there are the 
effects of climatic conditions and seasonal changes. Injurious insects 
sects and plant diseases greatly modify the results in alfalfa seed pro¬ 
duction. But these do not seem to explain why the yields of seed have 
decreased from former times. There is no perceptible climatic change, 
nor direct evidence to show that insects or diseases are responsible as 
a general cause. 
Conditions That Have Changed 
In canvassing the conditions that may have influenced alfalfa seed 
production, we find that the question of subsoil moisture is decidedly 
changed to what it was in the early days of alfalfa seed growing- 
Most of the land in Colorado, before being irrigated, had dry sub¬ 
soil to almost indefinite depths, but after the land had been irrigated 
for a number of years, an underground water table was established at 
varying depths from the surface according to the character of the soil 
formation. When alfalfa was first sown on land that had never been 
