Dung Beetle Improves soil Bacterial Diversity and Enzyme Activity and Enhances Growth and Antioxidant Content of Chinese Cabbage (Brassica rapa ssp. pekinensis)

Abstract

Dung beetles have been used to enhance soil health and crop growth and yields, but their effects on soil enzymology and microbial diversity are seldom reported. The present work reports on beneficial effects of dung beetles on soil enzyme activity, bacterial diversity and growth and antioxidant content of Chinese cabbage (Brassica rapa ssp. pekinensis). The soil amended with cow dung only (CD), or with dung broken down by dung beetles (DB), was compared with untreated control (CO). Soil bacterial diversity was determined through 16S rRNA gene sequencing, and enzymological tests were used for soil enzyme activity. Dung beetles significantly increased acid phosphatase, urease, cellulase, catalase and β-glucosidase activities in the soil compared with CD or control. Bacterial alpha-diversity significantly increased in DB when compared with CD or control. Microbial carbon (C) and nitrogen (N) were significantly higher in DB than in CD and in CD than control. The DB and CD treatments also significantly enhanced plant growth and the content of antioxidants (total flavonoids, polyphenols and vitamin C) and phytohormones indole-3-acetic acid (IAA), trans-zeatin riboside (ZR) and gibberellic acid (GA3) compared with control, while a significant reduction was noted in abscisic acid (ABA) in DB compared with CD or control plants. Correlation analysis confirmed that the enzyme activities are pH dependent, as pH was significantly lowered by DB compared with CD or control. Our results suggest that use of dung beetles in conventional practices could be an effective strategy to improve soil nutrient availability and microbial activity and antioxidant content of Chinese cabbage.