Pollination service and soybean yields

Abstract

Soybean is the most important crop for Argentina in terms of cultivated area and annually exported tons. Although soybean is autogamous, crop yields can be enhanced by pollinators. The aim of this study is to analyze the effects of insect pollination on soybean production. A pollination exclusion experiment (15 replications) was conducted to analyze the effects on seed production per plant in three stands located in the adjacence to a 100 Ha forested park, which was considered the main potential source of wild pollinators to soybean flowers. Fruits and seeds produced per plant –controlled by vegetative growth-were compared between plants with flowers open to pollinators and fully-caged plants (with flowers excluded from pollinators). A control treatment for the shading effect of the cages used for pollinator exclusion was also performed. Pollination was estimated by pollen deposited on stigmas. The number of pollen grains deposited on stigmas of open-pollinated flowers was higher than that of excluded flowers (27.3 vs 6.9 pollen grains per stigma, respectively). Reproductive variables (# of fruits and # of seeds per plant; total yield per plant) showed lower values (13–25% of reduction according to the variable) in excluded flowers compared to those from open-pollinated flowers. The contribution of biotic pollination to soybean production could be important because when pollinators are excluded pollen deposition and crop yields decrease. The soybean pollination service could be considered as part of the green infrastructure needed to maintain or to improve soybean yields.