Tomato cultivation substrates differ in stage-dependent root zone–rhizosphere coordination and biomass allocation

Introduction Cultivation substrates are commonly evaluated from their initial properties or final crop performance, leaving the developmental relationships among root-zone conditions, rhizosphere functioning, and plant responses poorly resolved. We examined how contrasting substrates were associated with changes in these components across tomato development. Methods Tomato ( Solanum lycopersicum L. cv. “22B”) was grown in greenhouse soil (SL), a composted pinecone residue substrate (PR), or a peat substrate (PS), with corresponding unplanted controls. Independent destructive sampling was conducted at Weeks 4, 8, 12, and 16 after transplanting. Root-zone physicochemical and nutrient conditions, rhizosphere enzyme activities, root traits, and organ dry matter were assessed across development; rhizosphere dehydrogenase activity, aboveground NO 3 -- N, P, and K accumulation and allocation, and yield-related traits were determined at maturity. Results Substrate effects were strongly stage-dependent. PR generally exhibited higher urease and sucrase activities during early-to-middle development. Fluorescein diacetate hydrolase activity was highest in PR at Weeks 4 and 8, but shifted to PS at Weeks 12 and 16. Throughout the growth cycle, PS generally maintained lower bulk density and higher gravimetric water content. It also exhibited the highest rhizosphere dehydrogenase activity at maturity and accumulated more stem, leaf, fruit, and total plant dry matter during late development, together with greater aboveground NO 3 -- N, P, and K accumulation at maturity. The estimated yield under PS reached 53,657.70 kg ha -1 , representing increases of 80.08% over SL (29,796.45 kg·ha -1 ) and 39.64% over PR (38,425.10 kg·ha -1 ). After accounting for substrate and developmental stage, significant associations were concentrated primarily between root-zone conditions and belowground biochemical and root responses, whereas total biomass showed no significant association with any single measured root-zone variable. Discussion These findings support a developmental-coupling perspective in which cultivation-substrate performance depends on the temporal coordination among root-zone conditions, rhizosphere biochemical functioning, and stage-specific crop demand rather than on static substrate properties alone. This perspective provides a developmental and process-level understanding of substrate-rhizosphere-plant interactions across tomato growth and offers a conceptual basis for stage-specific optimization of substrate selection and water and nutrient management in protected tomato production.