Agronomic Performances of Compost Associated with Pollinating Insects on the Growth and Yield of <i>Glycine max</i> (L.) Merril under Field Conditions

Abstract

Soybean is an oilseed crop legume cultivated for its benefits as a source of protein to human or animal food. The cultivation of soybean will promote the diversification of income sources for rural population. Like other crops, soybean flowers are visited by insects. It is expected that within the biodiversity conservation program, anthophilous insects including bees, generally increase fruit and seed yields of many plant species. Therefore, the effect of insect pollinators and compost on growth and yield parameters of Glycine max was assessed for two cropping seasons (2018 and 2019) in the field. The experiment was set up in a complete randomized block design with three treatments: subplots applied with compost; subplots applied with fertilizer-NPK; subplots applied neither with compost, nor with fertilizer-NPK. Two other treatments were designed by plants with flowers protected against insects or flowers pollination free. Results indicate that root nodules formed by soybean plants in plots that received compost were significantly higher ( P < 0.001) than those from positive and negative controls. During the 2018 and 2019 cropping seasons, 948 and 593 visits from five insect species were recorded on G. max flowers respectively. Lipotriches collaris was the most insect species frequently observed in the field, with 44.20% and 43.34% visits yearly respectively. The synergistic effect of insects and compost increased the number of seeds per pod by 28.27% and the percentage of normal seeds by 24.47%. Hence, applying Glycine max seeds at sowing with compost and in an environment with hives close to field could be recommended in agricultural development programs of farmers for a sustainable improvement of pods and seed yield of this valuable crop.