Contribution of honeybees to soybean yield

Abstract

Despite the economic importance of soybean [Glycine max (L.) Merr.], knowledge on the contributionof entomological pollination on seed yield is scarce. This study estimates the production of soybean resulting frompollination by honeybees (Apis mellifera L.) in two consecutive growing seasons in Paraná (Argentina). Experimentshad two treatments: excluded flower-visiting insects (EV) and non-excluded flower-visiting insects (NEV).The abundance of honeybees was similar in both years, although soybean production differed significantly(P < 0.05) between years. The NEV treatment out-yielded (P < 0.001) the EV treatment by 18% (5224 vs.4415 kg ha−1) in year 1, which was associated with an increase in the seeds per unit area but not with individual seedweight. In contrast, seed yield (on average 3830 kg ha−1) and seeds per unit area did not differ between treatments inyear 2. Individual seed weight was 3?5% (P < 0.05) higher in EV than in NEV in both years. The mechanismsinvolved in the seed yield increase could be related with pollen sterility in relegated flowers in secondary racemes orin distal locations of primary racemes under favorable conditions, as recorded in year 1. Thus, the action ofhoneybees carrying pollen from fertile flowers to relegated flowers may have increased the pod and seed set intreatment NEV in year 1.