A Three-Year Study of Comparative Effects of Four Organic Amendments on Soil Health Dynamics, Tomato Production, and Rhizosphere Microbial Community

Tomato is a demanding crop in fertilizers, fungicides, and pesticides. Therefore, producing food with limit use of chemical farm inputs became essential to reduce the harmful effects of these chemicals in agro-ecosystems. Green manures have great potential to limit the dependency on chemical inputs and preserve the soil fertility. Two fodder radish cultivars, used as green manure, were tested, during three consecutive cropping years, for their effects on soil properties and fertility, tomato growth and production, soilborne diseases' severity, and rhizosphere microbial community. Control treatment consisted of bovine manure and a commercial bio-activator of plant and soil systems i.e. biocat-15(CIRCLED LATIN CAPITAL LETTER R). All amended soils showed enhancement in their total nitrogen and available potassium and phosphorus levels. The highest increment in the soil organic matter and the soil carbon biomass noted using radish cv. Defender material. Before tomato planting, the monitoring of the soil microbial community structure revealed that the two green manures had increased the soil richness in actinomycetes communities but only cv. Defender had enhanced the bacterial population. For tomato growth and soilborne disease severity parameters, organic amendments had enhanced tomato growth by 17.8 to 41.7% and decreased disease severity by 46.6 to 97.3% at the second cropping year compared to the first one. The present results indicate that the four organic amendments tested would be an effective approach for improving the soil ecological environment for sustainable tomato cropping with significant enhancements of the majority of tested parameters recorded using fodder radish cv. Defender as green manure.