Plant-Soil-Microbe Interactions Following the Application of Organic Amendments in Vegetable Production Systems

The use of organic amendments is an increasingly common management practice in vegetable production systems. Organic amendments are typically mixed with soilless substrates or applied to field soil. As these materials break down, they provide essential nutrients for both plant and microbial growth. This practice impacts a number of soil physical properties which, in turn, affects root development, plant available water content, and microbial diversity and function. Currently, knowledge is lacking as to how these plant-soil-microbe interactions react to various types of organic amendments. Understanding how different organic amendments effect these inherently interconnected plant-soil-microbe relationships would provide valuable information to farmers as they evaluate their own management practices. Tomato (Solanum lycopersicum) plants were grown from seed in a popular local potting mix, transplanted into containers filled with a local field soil, and harvested at 7, 14, and 21 days after transplant. Both growing substrates were amended with one of four treatments: vermicompost, dairy compost, poultry pellets, and a non-amended control. The non-amended control treatment consistently led to the greatest plant growth. The organic amendments altered soil physical properties which, in turn, altered root growth, root architecture, soil matric water potential, and, as we hypothesize, microbial community composition. Multiple experiments conducted in this system showed that of the organic amendments studied, vermicompost led to the greatest plant height, total biomass, and root length density at all harvest dates after transplant. This study provides the framework for additional research exploring how modifying soil physical and hydrological properties by the use of organic amendments can have consequential effects on root growth and soil microbial communities, both of which are fundamental to successful crop production