Organic Mulching in Regenerative Agriculture Enhances Saprotrophs and Concomitantly Reduces Pathogenic Fungal Genera

Regenerative agriculture (RA) uses nature-friendly farm practices to nurture soil microbial communities. This study compared the fungal communities in RA plots with those in conventional agriculture (CA) and barren land (BL) plots (comprising completely barren- BL and with Eucalyptus - BL-Euc). Two crops - finger millets and vegetables (tomato/beans) were considered here. The RA farms identified for this study used diverse organic mulch applications such as farm manure, cow dung, cover-crop mulch, green-mulch, vermicompost, and so forth, for soil management. Internal Transcribed Spacer (ITS) amplicon sequencing analysis of soil DNA samples obtained from RA, CA and BL plots was done to identify fungal composition in each of the study plots. The fungal communities in RA finger millet and RA vegetable were compared with respective CA finger millet and CA vegetable and with BL plots. The fungal community in finger millet and vegetable RA plots showed high levels of diversity as well as species evenness. The RA plots in both crops showed a significant reduction in plant pathogenic fungal genera - Bipolaris and Pyrenochaetopsis. Furthermore, the RA finger millet plots contained specific Plant Growth Promoting Fungi (PGPF) – Rhizophlyctis and Agrocybe (saprotroph) and Acrocalymma (biotic and abiotic stress tolerance and plant growth and yield inducer), which were absent in finger millet CA and BL plots. Similarly, in RA vegetable plots, we found PGPFs including Mortierella (a biocontrol agent and plant nutrient solubilizer), Phoma (bioherbicide and plant growth promoter), and Pseudorobillarda and Torula (saprotroph), which were absent in the vegetable CA plots and BL plots. Results indicate that regenerative agriculture involving the use of organic mulch as soil amendment enriches beneficial fungi in soil, including saprotrophs, which in turn subdue the pathogenic fungal genera for healthier crop outcomes. The study points to the need for in-depth experimentation on individual organic mulches, through years of application and the associated development of microbial communities to identify best practices for agricultural sustainability.