Benchmark-Based Evaluation of Coir-Based Substrates for Low-Input Phalaenopsis Production under VWC-Threshold Irrigation

초록

Sphagnum moss is widely used for Phalaenopsis production, but interest in renewable alternative substrates has increased because of concerns regarding sustainability, supply stability, and production cost. This study evaluated seven substrate formulations for two Phalaenopsis cultivars under volumetric water content (VWC)threshold irrigation using sphagnum moss (SM) as a practical benchmark. 'Arihong' (AH) and 'Lovely Angel' (LA) were monitored on 12 measurement dates in SM, coconut husk chips (CS), coconut coir peat (CP), and four SMbased blends with CS or CP. Irrigation was triggered when device-reported VWC using the default calibration declined below 20%, with cumulative irrigation recorded as the water applied under this protocol. Baseline substrate properties, substrate-only moisture depletion, cumulative vegetative growth based on total leaf length area under the curve (TLL_AUC), endpoint biomass, root-zone pH and EC, and flowering performance were evaluated. Substrate formulations differed markedly in physical and chemical properties. CS had the highest air space and lowest container capacity, whereas SM2:CP1 had the highest container capacity and total porosity. Baseline chemical properties also differed among substrates, with CP showing high EC and P concentration and CS showing low EC. Under VWC-threshold irrigation, CS received the greatest recorded cumulative irrigation in both cultivars, reaching 160.7% of SM in 'AH' and 185.2% of SM in 'LA', while producing lower cumulative growth than SM. In contrast, SM2:CP1 showed a favorable descriptive irrigation-growth profile. In 'AH', SM2:CP1 received cumulative irrigation equivalent to 85.7% of SM with a numerically higher cumulative growth mean of 106.3% of SM. In 'LA', SM2:CP1 had a numerically higher cumulative growth mean of 112.6% of SM with only a modest increase in applied irrigation to 107.4% of SM. Endpoint biomass and observed flowering traits also indicated favorable performance of SM2:CP1, although flowering was evaluated only among survivors. Future studies should test these blends under independently replicated irrigation and commercial fertigation. These results indicate that partial replacement of sphagnum moss with coir peat at a 2:1 SM:CP ratio can provide a candidate sphagnum moss-coir peat blend for Phalaenopsis production under VWC-threshold irrigation, whereas coconut husk chips alone were associated with greater applied irrigation and lower plant performance.

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