Honey bee pollination improves the yield gaps of Guizotia abyssinica (Asterales: Asteraceae) in Ethiopia

Abstract Niger is an important oilseed crop, and its flowering phenology is highly responsive to cross-pollination. Honey bees (Hymenoptera: Apidae) are the crop's important pollinators due to their adaptation to wide environments. A comparative analysis was performed under field conditions to evaluate the effect of honey bee pollination and fertilizer application on the yield parameters of niger seed. The study was tested under different treatment conditions: (1) plots that were caged by honey bees and received fertilizer; (2) plots that were caged by honey bees but did not receive fertilizer; (3) plots that were restricted from any insect pollination but received fertilizer; and (4) plots that had free access to any pollinators and received fertilizer. The results showed that the mean number of primary branches and capitula per plant were highly significant (P < 0.05) among the treatments. A higher seed yield per ha was obtained in the treatment that received fertilizer and was caged with a honey bee colony (640 kg/ha). The oil content of the niger was higher (35.7%) for the treatment that was caged by honey bees for pollination but did not receive fertilizer. In this study, fertilizer application and honey bee pollination were both important in significantly increasing the seed set and seed yield of the niger plant. However, fertilizer application has less effect on the oil content of niger seed. Therefore, honey bee pollination must be considered in agronomical practices as a factor to sustain the yield and oil content of niger seed.