Impact of Long-Term Cover Cropped Organic Farming Practices on the Development of Disease Suppressive Soils

Numerous field studies have reported the disease-suppressive properties of the system in organic farming and cover crop practices. This research examined how long-term organic farming with cover-cropped systems enhance soil disease suppressiveness and changes the chemical composition of the rhizo-sphere related to disease resistance. The study proposed that the interactions between plant exudates and helpful microorganisms in these systems create conditions that are less favorable for harmful pathogenic organisms, resulting in soil that suppresses disease. To achieve the goals, we used an untargeted metabolomics approach to compare chemical profiles from long-term certified organic fields, including different cover crop termination methods like flail and rotary mowing, to conventionally managed plots. We analyzed rhizosphere soil extracts using ultra-high-pressure liquid chromatography combined with high-resolution mass spectrometry (UPLC-HRMS). We processed data with both MS-DIAL and XCMS, which included peak detection and feature grouping. We annotated metabolites using the MS-DIAL Public VS17 libraries for features derived from MS-DIAL and the METLIN database for features derived from XCMS. Our analysis identified over 2500 distinct soil compounds, showing that long-term cover cropping significantly changes the soils chemical environment. The treatments with cover crops showed a higher abundance and diversity of bioactive chemicals compared to the controls, and this enriched metabolic profile supported the formation of disease-suppressive soil.