Influence of herbicide on rhizospheric microbial communities and soil properties in irrigated tropical rice field

Microbial diversity is an essential biological indicator of soil health as well as crop productivity and helps in maintaining the ecosystem dynamics. In land management, Nature based Solutions (NbS) are not mainstream management, however, for sustaining the balanced ecosystem, integrity in the structural and functional diversity of microbes via NbS is imperative. Direct seeded rice (DSR) cultivation is a promising technique for efficient rice production, but weed infestation can lead to yield loss, requiring extensive herbicide use like pendimethalin (PND) and pretilachlor (PRT). The results revealed that with a reduction in PND and PRT residues (0.93-0.01 mu g g- 1 soil), values of soil microbial biomass C (132.3-112.6 mg kg- 1 soil) and MBN (12.6-8.5 mg kg- 1 soil), and enzyme activities increased. Negative correlations were observed between herbicide residues and microbial parameters. In control soils, higher population sizes of archaea, bacteria, and fungi were obtained compared to herbicide-treated soils. High-throughput amplicon sequencing (16S rRNA, ITS genes) detected dominant archaea, atronorbrum_4312, MethanothrixX_B, and Methanosarcina_2619 in herbicide treated whereas Nitrosocosmicus, Methanoregula, in control. Bacillus, Methyloceanibacter, Azospira, and Nitrospira bacterial genera were present in both groups. Control soil showed the dominance of Humicola, Nigrospora, and Paramyrothecium fungi, while treated one exhibited Mariannaea, Ceratobasidium, Funneliformis (PND), Aspergillus, Pseudorhypophila, and Lecythophora (PRT). Overall, herbicides had a detrimental impact on microbial dynamics, and their residues correlated negatively with soil variables and microbial diversity. The research outcomes revealed the dramatic variations in microbial communities under the influence of herbicides. This will further aid in a better understanding of the development of NbS solutions for effectively managing herbicide application in direct-seeded rice for enhancing soil health and ecosystem services while supporting sustained productivity.