Influence of Alternate Wetting and Drying Irrigation and Microbial Fertilizer on Weed and Canopy Arthropod Diversity in Paddy Fields in Southern China

Rice is one of the major grain crops worldwide, while intensive cultivation has caused severe loss of weed and arthropod diversity, making rice fields more susceptible to weed and pest infestations. Understanding the response of weeds and arthropod diversity to different management practices is crucial for green rice production. In this study, a two-year field investigation was conducted in a typical paddy field in the Poyang Lake Basin. The community composition and diversity of weeds and arthropods under different water and fertilizer management practices were explored. The results demonstrated that alternate wetting and drying (AWD) irrigation and microbial fertilizer (MF) effectively reduced total weed density while enhancing Margalef richness (DMG), Shannon–Wiener (H′), Simpson dominance (S), and Pielou evenness (E) indices. The most dominant weeds, namely Monochoria vaginalis, were significantly suppressed. However, AWD irrigation may increase the density of Echinochloa crus-galli. For the arthropods, AWD irrigation and MF reduced the populations of pests by suppressing hygrophytic pests, such as Chlorops oryzae and Aeschyntelus chinensis. The DMG, H′, and S of natural enemies were greatly improved, exceeding those of pests in both years. Overall, the AWD irrigation and MF can suppress harmful weeds and pests, while enhancing weed and arthropod biodiversity.