Monospecific cover crops perpetuate soil biotic homogenization in croplands across diverse soils

Croplands are known to support significant soil biotic homogenization. Cover crops are commonly used as a sustainable agriculture practice; however, many times these cover crops are composed of single‐species. Unfortunately, the influence of monospecific cover crops on soil biotic homogenization remains virtually unknown. Here, we performed a common garden experiment including soils from 27 agricultural fields across mainland China and two major cover crops grown separately in monoculture: a legume ( Vicia villosa Roth) and a gramineae ( Lolium multiflorum Lam.). We found that, on average, monocultures of both legume and gramineae cover crops significantly promoted soil biotic homogenization (i.e. lower β diversity) for bacteria, fungi and protists compared with control soils without cover cropping ( p < 0.05). Moreover, gramineae cover crops also promoted multifunctionality homogenization (i.e. lower β multifunctionality), which was also connected with increasing biotic homogenization. Conversely, legume cover crops reduced the homogenization of bacterial generalists, thereby mitigating multifunctionality homogenization. Importantly, the homogenizing effects of monospecific cover crops on soil communities and multifunctionality were counteracted by the heterogeneity of initial soil properties, highlighting its key role in maintaining ecological heterogeneity. Our results suggest that monospecific cover crops contribute to soil biotic homogenization across diverse soils under controlled greenhouse conditions, with profound implications for managing soil biodiversity and ecosystem functioning in agroecosystems. Read the free Plain Language Summary for this article on the Journal blog.