In a randomized complete block design (3 replicates, 15 modules, two crop cycles), drip irrigation (DI) nutrient solution carried the highest aerobic plate counts in both seasons β fall 5.9 Β± 1.01 and spring 5.44 Β± 0.6 log10 CFU/mL β while ebb-and-flow was lowest (range 2.39β2.6) . Community composition was shaped by system (RΒ² = 0.254), system Γ season interaction (RΒ² = 0.105), season (RΒ² = 0.053), sampling day, and temperature, all p = 0.001; pH did not affect composition or Shannon diversity but was negatively associated with APC (β0.36 log10 CFU per pH unit, 95% CI β0.54 to β0.18) .
Reported DI means are graphed; fall APC ranged 2.39β7.47 and spring 2.6β6.43 log10 CFU/mL across systems, but per-system means for the other four systems were not numerically disclosed in the extracted text.
Core richness diverged sharply: DI had 292 core ASVs versus 15 each (DWC, EF, KR) and 11 (NFT), yet only Acidovorax was present in every sample (0.14β7.3% mean abundance). Network analysis identified 17 hub ASVs spanning 14+ genera; Acidovorax, Legionella, and Caulobacter appeared as both core and hub taxa via distinct ASVs, suggesting strain-level ecological differentiation . High-abundance Methylophilus and Eoetvoesia were neither core nor hub β the authors interpret them as opportunistic responders to root exudate pulses rather than persistent keystone members.
Confidence: Moderate. Findings are internally consistent, statistically explicit, and concordant with an independent Ohio commercial-facility study cited by the authors, but two seasons Γ one crop Γ one site limits generalization, and key effect claims rest on a design where substrate type and delivery mode are confounded within DI.
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