Ergothioneine dynamics in a long-term farming systems trial: Effects of tillage, management, and oxidative stress on grain and soil ergothioneine

This study investigated how long-term farming systems and tillage practices regulate ergothioneine (ERGO) dynamics in agricultural soils and grains, considering microbial mediation and oxidative stress interactions. The work was conducted in the Farming Systems Trial (FST) at the Rodale Institute using a split–split plot randomized complete block design comprising three farming systems, conventional (CNV), legume-based organic (LEG), and manure-based organic (MNR), under two tillage intensities, full tillage (FT) and reduced/conservation tillage (RT). The analysis was cross-sectional across treatments. Grain and soil ERGO were quantified using UPLC–MS/MS, microbial communities were assessed by PLFA profiling, and herbicide-induced oxidative stress was represented by a semi-quantitative Oxidative Stress Exposure Index (OSEI) derived from literature-based toxicity weights. Grain ERGO concentrations and partitioning coefficient were highest in CNV–RT systems, where herbicide exposure (glyphosate, atrazine, 2,4-D) increased oxidative stress. Organic systems maintained higher microbial biomass and residual soil ERGO but lower grain partitioning efficiency, indicating that microbial enrichment improves ERGO supply but not necessarily plant uptake. Reduced tillage enhanced grain ERGO across systems, consistent with increased arbuscular mycorrhizal fungal (AMF) activity. The weak correlations between microbial biomass and grain ERGO (R² < 0.2) suggest that oxidative signaling, rather than total microbial abundance, governs ERGO uptake. A weak negative association between soil organic matter and ERGO Partitioning Coefficient indicates that biologically buffered soils reduce oxidative demands in plants. Overall, ERGO accumulation in grain reflects the interaction between soil microbial context and plant oxidative status. These findings suggest that oxidative stress is a key management-responsive factor linking tillage practices, farming systems, soil health, and crop ERGO partitioning between soil and grain pools.