Efficiency of dung beetles (Coleoptera: Scarabaeidae) in improving soil and forage grasses by incorporating nutrients through the removal of cattle dung

Coprophagous dung beetles provide important ecosystem services in improving soil quality and plant development in agricultural environments due to the availability of nutrients from dung removal. The study aimed to compare the effect of dung removal performed by two functional groups, among themselves and with mineral fertiliser, on improving soil and forage grass characteristics. An experiment in mesocosms was conducted in Southern Brazil during the summer/autumn of 2021, sowing Urochloa brizantha in the treatments: (1) telecoprid species (Canthon rutilans cyanescens), (2) paracoprid species (Dichotomius sericeus), (3) both species together, (4) mineral fertiliser and control with cattle dung. Dung removal was quantified weekly. At the end of the experiment, the soil's physical, chemical and microbiological characteristics, dry biomass and macronutrients (N, P and K) of the leaves and roots, and photosynthetic pigments of grasses were analysed. The dung beetle species studied increased total nitrogen and organic matter contents and their particulate fractions of C and N. Paracoprids decreased the soil bulk density and improved its soil aggregation, influencing the pH and Mg contents, with a reduction in Al levels. They were as efficient as mineral fertiliser in incorporating K into the soil. Treatments with beetles had values similar to mineral fertiliser in the foliar concentrations of P, and paracoprids promoted increases in the K concentration in the leaves and roots of the grass. This functional group was also more efficient in removing cattle dung, which was positively related to the amounts of N, organic matter and its particulate fractions, P, macroaggregates and the cation exchange capacity (CEC_pH7.0) of the soil. Thus, dung removal was associated with improvement in the soil, mainly paracoprids, reinforcing the importance of the ecosystem functions performed by these organisms in agricultural environments, where they can contribute to the increase in nutrient cycling with a consequent decrease in the use of mineral fertilisers.