Evaluation of the indigenous microorganisms in soilless culture: occurrence and quantitative characteristics in the different growing systems

Quantitative characteristics such as population density and population dynamics of the indigenous microorganisms in four types of soilless tomato production systems were investigated. For non-specific genera, the amount of the population of aerobic bacteria and fungi in root was 9.2–10 and 4.2–5.5Logcfug−1, respectively, regardless of the location of samples collected. For the specific genera, however, fluorescent pseudomonads showed the highest population density (5.4Logcfug−1) followed by Fusarium spp. (2.5–3.7Logcfug−1) and Pythium spp. (2.3–2.8Logcfug−1). Population of microorganisms was significantly different between soilless culture systems as well. The coconut-fiber system (organic substrate culture) showed the highest amount of fungi and Fusarium spp., whereas the rockwool system (inorganic substrate culture) contained the highest amount of fluorescent pseudomonads. Solution culture, DFT and NFT, contained higher amounts of Pythium spp. than the substrate cultures throughout the experiment. NFT also contained the largest population of Fusarium spp. compared to the other ones. In population density investigation, aerobic bacteria in roots became equilibrium at 10Logcfug−1 in all systems under investigation, however, fungi tended to increase until the end of experiment. The results indicated the unique indigenous microorganisms population in each soilless system. Also, it revealed that aerobic bacteria could be dominant over fungi in inorganic substrate culture. With further research of beneficial microorganisms to horticultural plants, biological control with reduced fungicide application in soilless culture would be feasible.