Soil macrofauna and microbial communities respond in similar ways to management drivers in an irrigated maize system of Colorado (USA)

Abstract

The adoption of conservation agriculture has gained considerable attention due to growing interest in managing soil biological diversity and overall soil health. However, there is limited understanding of how practices such as conservation tillage and residue retention affect soil biota across different spatial scales and are associated with alterations to other soil properties. In this study, we examined changes in soil physicochemical properties, soil macrofauna, and microbial communities at two soil depths (0–10 cm, and 10–20 cm) in a 6-year field experiment manipulating tillage and maize residue management. The following treatments were included in the experiment: no-till with residue retention; no-till with residue harvest; conventional tillage with residue retention; and conventional tillage with residue harvest. Macrofauna taxa were identified and estimated visually, while bacterial and fungal communities were identified and analyzed using high throughput sequencing and multivariate statistics including non-metric dimensional scaling and indicator species analysis. Soil physicochemical properties measured include soil carbon and nitrogen, soil moisture, permanganate oxidizable carbon, available soil phosphate, pH, electrical conductivity and aggregate stability. Residue retention increased macrofauna abundance and diversity across soil depths and tillage treatments. Fungal diversity was also highest under residue retention in the topsoil (0–10 cm), while bacterial diversity was generally higher under conventional tillage. Residue retention was the main driver of macrofauna and microbial community composition, while an interaction between tillage and residue management indicated that the effect of tillage on microbial communities was most pronounced when residues were retained. Soil carbon and nitrogen, aggregate stability, permanganate oxidizable carbon, soil moisture content, available soil phosphate and soil electrical conductivity were all enhanced under residue retention in the topsoil. Indicator species analysis suggested that macrofauna taxa belonging to Annelida, Aranaea and Chilopoda together with bacterial phyla Fibrobacteres and fungal phyla Rozellomycota were indicators for no-till combined with residue retention, while Coleoptera, Spirochaetae and Basidiomycota were indicators for conventional tillage with residue retention. Multivariate analyses suggested that total macrofauna abundance, soil carbon and pH were strongly associated with bacterial and fungal community composition in the topsoil layer. Co-inertia analysis indicated significant covariation between soil physicochemical, macrofauna, bacterial and fungal datasets, suggesting a strong association between different soil parameters and cascading effects of management on multiple soil properties. Our findings demonstrate that residue retention enhances soil biological, physical and chemical properties and that communities of soil macro- and microorganisms tend to respond in similar ways to these management interventions.