Soybean yield is increased through complementary pollination by honey bees

Abstract

Brazil is the major global soybean producer with ca. 40 million hectares grown annually. In recent years, there has been a growing interest by beekeepers to migrate their hives close to soybean fields, to allow honey bees, Apis mellifera L. 1758 (Hymenoptera – Apidae) to forage in. To understand the effect of honey bee pollination on the soybean yield, one experiment was set up in Londrina, Brazil, to assess the yield of soybeans and its components, whose flowers were visited by honey bees, compared to those not visited. The experiment was repeated for three consecutive years, during the 2017 to 2020 soybean growing seasons. Treatments consisted of (1) open plots, with free access by honey bees; (2) caged plots with a honey bee hive inside; and (3) caged plots with no access by honey bees or any other pollinator. Monitoring visits by honey bees to soybean flowers indicated consistent visits in open and caged plots with a beehive, and larger numbers of honey bees were observed visiting soybeans at 11 am. The average yield for the three years revealed a significant increase when honey bees had access to flowers: 5,565 kg/ha for caged plots with honey bees and 5,201 for open plots, compared to caged plots without honey bee hives, which yielded 4,926 kg/ha. The yield increase was mainly associated with the occurrence of more 3 and 4-seeded pods, a larger number of seeds/pod and seed weight, as well as a smaller number of pods with zero or one seed observed in treatments with the presence of honey bees, compared to the caged plots without beehives.