Soybean and Bees

Some authors commented that the low number of pods as related to the previous number of
flowers (normally around 10-15%), might be attributed to a pollination deficit, thus reducing
the soybean yield (McGregor, 1976; Free, 1993; Delaplane and Mayer, 2000). In contrast,
Abernathy et al. (1977) reported that failure of fertilization is insignificant as a cause of floral
abscission in soybean. Abscising flowers were mostly all fertilized and usually contained
proembryos that had undergone two or three cell divisions.
Bees and soybean yield
Despite the above-mentioned regarding normally low levels of cross-pollination, soybeans
are sometimes referred as partially dependent on insect pollination (Klein et al. 2003; Gallai
et al., 2009; ISSA, 1984). Lautenbach et al. (2012) reported benefits of insect pollination
on soybean, in Brazil, Argentina, India, China and USA. Robacker et al. (1982, 1983) refer that
investigations have shown higher soybean yields when bees were introduced in the field for
pollination purposes, despite restrictions on the methodology used on those studies.
Soybean yields have been shown to be influenced by honeybee visitation (vila, 1988; vila
et al., 1992). Yields of three varieties grown in Indiana were increased about 17.2% up to 32
m of honeybee colonies (Abrams et al., 1978) and the rate of yield increases declined rapidly
beyond a 32 m radius from the colonies. In Wisconsin, two cultivars, Corsoy and Hark,
yielded 14.8% and 16.4% increases, respectively, in cages with honeybees over those without
(Erickson, 1975a, c). However, there were no significant increases in the yield of ‘Chippewa
64’. In cage trials with ‘Pickett 71’ in Arkansas and Missouri, 15% more beans were produced
in cages with bees than in cages without bees (Erickson et al., 1978) (Tables 4 and 5). In the
same study, yields in open-field trials with ‘Forrest’ and ‘Lee 68’ were significantly higher at
distances of up to 100 m from apiaries.
Table 4. Treatment Yield Means (g) for Thrashed Samples of 3.05 m of Row.
Year/Cultivar With bees Without bees Open Plots Bees/No bees (%) N
1971
Chippe
588 627 630 -6.6% 6
wa Corsoy 762 669 676 13.9%** 6
1972*
Hark 783 744 797 5.2% 9
1973
Hark 500 430 480 16.3%** 9
* Dry spring, poor germination, nonuniform stand. ** Significant at the 0.05 level.
Source: Erickson, 1976.
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