New Generation Herbicides and Their Impact on Soil Health and Crop Ecosystem: A Comprehensive Review

Abstract

New generation herbicides—broadly interpreted as modern active ingredients and formulations introduced or widely adopted since the mid-2000s to address evolving weed pressures, regulatory constraints, and resistance—have reshaped weed management across major cropping systems. Their agronomic appeal lies in high efficacy at comparatively low use rates, compatibility with conservation tillage, and increasing integration with herbicide-tolerant crop traits and precision application technologies. At the same time, concerns persist regarding unintended impacts on soil health and the wider crop ecosystem, including rhizosphere microbiomes, nutrient cycling functions, soil fauna, and non-target biodiversity. This review synthesises evidence from 2006–2026 on how contemporary herbicides and their mixtures influence key soil health indicators, with emphasis on microbial diversity and network structure, enzyme activities, functional genes involved in nitrogen transformations, and the ecological consequences of residues, metabolites, and off-target movement. Case evidence is discussed for representative modern herbicide groups and practices, including auxin herbicides (dicamba and 2,4-D systems), HPPD inhibitors (mesotrione and tembotrione), and PPO inhibitors (saflufenacil), alongside studies on mixtures and mitigation tools such as sorbent amendments. Across the literature, effects on soil biological properties are often transient and context dependent, shaped strongly by soil organic matter, moisture regime, prior use history, formulation, and mixture complexity. However, repeated exposure and realistic mixtures can measurably alter community composition, microbial interaction networks, and nitrogen cycling endpoints, suggesting that soil health risk assessment should move beyond single-compound tests and incorporate functional microbial indicators and agroecosystem feedbacks. The review concludes with stewardship and research priorities aimed at aligning herbicide innovation with soil health protection and resilient cropping systems.