Deciphering insights into rhizospheric microbial community and soil parameters under the influence of herbicides in zero-tillage tropical rice-agroecosystem.

Extensive use of chemicals like herbicides in rice and other fields to manage weeds is expected to have a lasting influence on the soil environment. Considering this rationale, we aimed to decipher the effects of herbicides, Pendimethalin and Pretilachlor, applied at 0.5 and 0.6 kg ha, respectively on the rhizosphere microbial community and soil characteristics in the tropical rice field, managed under zero tillage cultivation. The quantity of herbicide residues declined gradually since application up to 60 days thereafter it reached the non-detectable level. Most of the soil variables viz., microbial biomass, soil enzymes etc., exhibited slight reduction in the treated soils compared to the control. A gradual decline was observed in Mineral-N, MBC, MBN and enzyme activities. Quantitative Polymerase Chain Reaction results showed maximal microbial abundance of bacteria, fungi and archaea at mid-flowering stage of rice crop. The 16 rRNA and ITS region targeted amplicons high throughput sequencing microbial metagenomic approach revealed total of 94, 1353, and 510 species for archaea, bacteria and fungi, respectively. The metabarcoding of core microbiota revealed that the archaea comprised of Nitrososphaera, Nitrosocosmicus, and Methanosarcina. In the bacterial core microbiome, Neobacillus, Nitrospira, Thaurea, and Microvigra were found as the predominant taxa. Fusarium, Clonostachys, Nigrospora, Mortierella, Chaetomium, etc., were found in core fungal microbiome. Overall, the study exhibited that the recommended dose of herbicides is not found to be detrimental to the microbial dynamics, though a negative relation between residues and soil variables was observed that might alter the microbial diversity. The outcomes offer a comprehensive understanding of how herbicides affect the microbial community in zero tillage rice soil, thus has a critical imputation for eco-friendly and sustainable rice agriculture. Further, the long-term studies will be helpful in elucidating the role of identified microbial groups in sustaining the soil fertility and crop productivity.