Effects of Substrate-Based Root Restriction on Tomato Growth, Fruit Quality, Yield, and Microbial Communities in a Simplified Automatic Soilless Cultivation System

Root restriction is an agronomic technique that influences plant morphology, physiology, and productivity. This study investigates the effects of root restriction on tomato growth, fruit quality, yield and rhizosphere microbial communities using three distinct substrates: sand, soil, and peanut shell substrate (PSS), within a Simplified Automatic Soilless Culture System (SAS). The results showed that root restriction increased soluble sugar, protein, and lycopene content in tomato fruits, but reduced fruit yield. Evaluation using TOPSIS (Technique for Order Preference by Similarity to Ideal Solution) revealed optimal root-restriction levels for different substrates: 8cm peanut shell substrate >24 cm soil >8cm sand. Correlation analysis revealed significant relationships between root restriction height and substrate water holding capacity, total water storage and yield. Microbial amplicon sequencing revealed higher rhizosphere microbial diversity in tomatoes grown in soil and peanut shell substrate compared to sand. These three types of growing media (soil, sand, and peanut shell substrate) establish the rhizosphere of bacterial and fungal communities by selecting specific microbial taxa. Changes in container height drive the reduction-oxidation functional divergence of bacterial communities, affecting the connectivity and complexity of microbial networks.