A 7% increase could be a useful increase for a grower, though small. But my
overall conclusion is that this bee is a pretty good pollinator for alfalfa,
and the risk of increased self pollinations is surprisingly low when standing
crop is high. This has been the conclusion for quite a few plants in natural
systems as well.
For further information, see:
Strickler, K. 1999. The impact of flower standing crop and pollinator movement
on alfalfa seed yield. Environ. Entomol. 28(6): 1067-1076.
Strickler, K. and J. Vinson. 2000. A simulation of the effect of pollinator
movement on alfalfa seed production. Environ. Entomol. 29(5):907-918. (PDF