> We have a very mixed plant community for our bees.  This includes
> alfalfa. This past year we had enough alfalfa blooming that I
> watched it very close. As long as the bees had other forage blooming
> they would not use the alfalfa.  When I started collecting seed this
> fall the alfalfa was almost totally devoid of seed.  Most years I
> can collect several pounds of a very tough drought resistant alfalfa
>  seed.  The big difference this year was sainfoin.  Its bloom period
>  totally overlapped with the alfalfa.

Interesting observations, and you are right.  Sanfoin is very attractive
to honey bees. I have some in my yard and it takes care of itself, too.
  I planted it twenty years ago,.

Competition from non-target crops is a problem everywhere pollination is
attempted and the effects of competition can be unpredictable.
Competition from other crops may vary from region to region, from year
to year, and with the recent history of the hives in question.  Time of
day can be a big factor as well, as some plants only secrete at certain
times of day.

To try to avoid having competing plants draw away the bees intended for
pollination of high value crops, those crops requiring pollination are
planted where possible in locations which are expected to be distant
from competing crops where possible.  Longer flying distances decrease
the attractiveness of a crop.  Proximity increases attractiveness.

Different varieties of the same crop can vary considerably in
attractiveness.  Climate and weather factors as well as the type of soil
may affect attractiveness of a crop, too.

Moreover, individual bees develop loyalty to particular plant varieties
and may not switch easily as long as the earlier-blooming plant is yielding.

To manage these issues, bees for pollination are intentionally brought
in only after the target crop is in bloom, and the hives are placed
close to the target crop and spaced throughout that crop if the field is
large.

Where we are located, alfalfa is often the only blooming crop in an area
during some periods and we find the bees work it readily, but alfalfa
does not provide much pollen.  Therefore, we try to have other sources
of nectar and pollen nearby if we can and we don't much care if and when
they work any particular crop as long as they work and gain weight.

In times past, in Southern Alberta, honey bees were the sole pollinators
of the alfalfa seed crops and were very effective, but at that time
there was much less rapeseed was grown. Canola had not yet been
developed back then.

FWIW, rape would have been a strong competitor to alfalfa, but
beekeepers hated rape as the honey was quite unpleasant and avoided it
as much as possible.  Before the double zero varieties were bred, rape
oil was not suitable for food and the oil was used industrially.

Currently, Canolas, direct descendants of rapeseeds are in high demand
for meal and oil for livestock and human diets and blooming Canola crops
are sought out by beekeepers for the high quality, light coloured honey
produced.  Canola is an example of a very successful plant breeding
program that achieved great success in a mater of only a decade or so.

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