Transmission of antibiotic resistance through organic amendments in arable land: A 3-year field study with pigeonpea-wheat cropping system.

The worldwide emergence of antimicrobial resistance (AMR) poses a substantial risk to human health and environmental stability. In agriculture, organic amendments (derived from organic sources such as manure, and plant residues) are beneficial in restoring soil properties and providing essential nutrients to crops but raise concerns about harboring antibiotic resistance, which emphasizes the need for vigilant monitoring and strategic interventions in their application. The current study assessed the impact of farming practices (organic and conventional) in a three-year field experiment with pigeonpea-wheat cropping system, focusing on the transmission of AMR using culture-dependent and -independent approaches, and soil nutrient content. Markers for antibiotic resistance genes (ARGs) (aminoglycoside-aacA, ß-lactam-blaTEM, chloramphenicol-cmlA1, macrolide-ermB, sulfonamides-sul1, sul2, and tetracycline-tetO) and integrons (intl1 and intl2) were targeted using qPCR. Manure amendments, particularly FYM1, exhibited a higher abundance of copies of ARGs compared to the rhizospheric soil. Organic farming was associated with higher copies of intl2, sul1, blaTEM, and tetO genes, while conventional farming showed increased copies of sul2 and ermB genes in the rhizosphere. Significant positive correlations were observed among soil nutrient contents, ARGs, and MGEs. The notable prevalence of ARGs linked to manure amendments serves as a cautionary note, demanding responsible management practices.

Organic amendments modulate the crop yield and rhizospheric bacterial community diversity: a 3-year field study with Cajanus cajan / Las enmiendas orgánicas modulan el rendimiento de los cultivos y la diversidad de la comunidad bacteriana rizosférica: un estudio de campo de 3 años con Cajanus cajan

Excessive use of chemicals to enhance soil nutrient status and crop yield has resulted in a decline in soil health. Organic farming promotes organic amendments, which help to balance the ecosystem. Understanding the dynamic patterns of belowground microbial populations is essential for developing sustainable agricultural systems. Therefore, the study was designed to evaluate the effect of different agri-practices on rhizospheric bacterial diversity and crop yield in an Indian agricultural system. A 3-year field experiment was set up in a randomized block design using Cajanus cajan as a model crop, comparing conventional farming with organic practice (with animal manure and bio-compost as amendments). Plant and rhizospheric soil samples were collected at the harvest stage for assessing various growth attributes, and for characterizing rhizospheric bacterial diversity. Enhanced crop productivity was seen in conventional farming, with a 2.2-fold increase in grain yield over control. However, over the 3 years, an overall positive impact was observed in the bio-compost-based organic amendment, in terms of bacterial abundance, over other treatments. At the harvest stage of the third cropping season, the bacterial diversity in the organic treatments showed little similarity to the initial bacterial community composition of the amendment applied, indicating stabilization along the growth cycles. The study emphasizes the significance of the choice of the amendment for ushering in agricultural sustainability.(AU)