Root-Rot Outbreak in a Recirculating Vertical Farm

Reservoir & Loop Controls

Recirculation flow rate 2.0 L/min

UV-C sterilizer power 40%

Reservoir volume 80 L

Live Readouts

Reservoir spore index

0.0

Avg. infected roots

0.0%

Estimated yield loss

0.0%

Per-Tier Root Infection

How it works

A stacked NFT (nutrient-film-technique) vertical farm shares one nutrient reservoir: a pump lifts water past a UV-C sterilizer to the top tier, and gravity carries it down through each tier's channel in turn before it drains back into the reservoir. Any tier with infected roots sheds pathogen propagules (e.g. Pythium zoospores) into the film as it passes — so contamination accumulates tier by tier on the way down, and the reservoir sees the sum of everyone's runoff.

after UV:      C0 = Cres · (1 − uv)
cascade down:  Ci = Ci-1 + shed·fi / flow      (i = tier 1..4, top→bottom)
tier infection: dfi/dt = k_inf·Ci·(1−fi) − k_rec·fi
reservoir mix:  dCres/dt = (flow/V)·(C4 − Cres) − k_decay·Cres

Flow rate — faster flow dilutes each tier's shed contribution per pass (lower Ci rise) but also completes more loops per minute, so its net effect on containment depends on the UV dose it buys.
UV-C power — kills a fraction of spores every time water passes the sterilizer, before it ever reaches the top tier — the only variable that removes pathogen from the loop rather than just diluting it.
Reservoir volume — a bigger tank has more buffering capacity, so a given spore load raises the mixed concentration less (division by V).
Outbreak button — seeds infected root mass at the top tier; because the top tier's runoff contaminates every tier below it, an untreated outbreak that starts at the top is worse than one starting at the bottom.

This is the same reasoning greenhouse and vertical-farm growers use to size in-line UV sterilizers and decide reservoir turnover schedules — a shared recirculating loop turns a single infected root ball into a whole-system risk.

Healthy roots Infected roots UV-C sterilizer

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