Assessing the potentials of agricultural ecosystem pollination services to improve bean yield in smallholder farming systems

Abstract

Pollination services by insects contribute to production in 75% of food crop species. When promoted through agro-ecological intensification (AEI), pollination can narrow yield gaps in smallholder farming systems. The study evaluated the contribution of insect pollinators on common beans (Phaseolus vulgaris L.) yields, and the knowledge gaps pre and post-training of smallholder farmers (n=300) in pollinators and field margins in a bean agro-system were investigated. Also, the role of field margin as a refuge for flower-visitors, and how plants and pollinator richness and diversity can influence strength of pollination networks in three agro ecological zones were investigated. Baseline and end-line surveys, pollinator exclusion and fluorescent dye-experiments, insects and vegetation surveys were carried out to obtain data for each specific objective of the study. While the majority of farmers were unaware of pollinators and their importance as pollinators before training, the end-line survey one year after training showed an increase in knowledge. The majority of farmers subsequently recognized honeybees, hoverflies and solitary bees, by names and their role as crop pollinators and natural enemies (for the case of hoverflies). Higher yield based on pods per plant and seeds per pod on open pollinated and hand pollinated flowers were significantly recorded compared with plants from which pollinators had been excluded suggesting that pollinators contribute significantly to crop yield. Similarly, it was found that field margin plants are essential in supporting higher number of pollinator taxa and can influence their richness in adjacent bean field. Collectively these results showed that improving understanding among smallholder farmers of ecosystem services and their ecological requirements are both feasible and essential for conservation of insect pollinators, which are important for optimising yield in this production system, and that crop margin vegetation provides habitat for these ecosystem service providers. Field margins with high plant diversity displayed extended and more robust pollination networks compared to those with low plant diversity, and consequently these habitat strips should be managed with sensitivity for pollinating insects and for the stability and persistence of plant-pollinator interactions in this agro-system.