Effects of different earthworm ecotypes on soil nutrients distribution under straw return management in a maize agroecosystem

Abstract Earthworms are among the most common soil macrofauna taxa in cropland areas in the Loess Plateau and exert a large influence on soil nutrient cycling. The impacts of earthworms are related to the way different earthworm ecotypes process the soil. However, there are relatively few studies on the differing impacts of earthworm ecotypes on soil nutrient dynamics. Here we carried out a field plot experiment to explore the characteristics of soil nutrients, microbial populations, and enzyme activity subjected to two ecological groups (epigeic and epi‐anecic) in a maize system under two typical straw return managements (straw mulching and incorporation). Epigeic (EP), epi‐anecic (EN), and the combined presence of epigeic and epi‐anecic earthworms (EM) increased soil nutrients, microbial populations, and enzyme activity and improved maize growth. Under the straw incorporation mode, the promotion effect of earthworm treatment shows: EM > EN > EP. Compared with CK, EM significantly increased the nutrient content of all soil layers, and the activities of invertase, urease, phosphatase, and catalase increased by 8.6%–38.5%, 5.8%–33.7%, 13.7%–32.4%, and 8.1%–36.2%, respectively. The abundance of soil bacteria, actinomycetes, and fungi increased by 21.8%–37.7%, 11.7%–43.6%, and 46.2%–58.1%, respectively. Under straw mulching conditions, EP significantly increased the nutrient content, enzyme activity, and microbial content in the 0–10‐cm soil layer. The results showed clear effects of the earthworm ecotype on soil fertility under different straw application methods. These findings are helpful for revealing the role of different earthworm ecotypes in the nutrient cycling processes of dryland farmland ecosystems.