F2 crop steering: the daily operating manualF2 crop steering: the daily operating manual

What this system is, and what crop steering means

F2 is an autonomous irrigation controller for a veg grow room. It is software that reads moisture and salt probes in the root zone and decides, on its own, when to fire a watering shot through a pump and valves. You set the targets. It does the watering.

Crop steering means pushing the plant toward one of two kinds of growth by controlling exactly how and when it waters. Vegetative steering (bulking) keeps the medium wet with many small waterings and only a small drying-out. Generative steering (the flower or stress push) uses a bigger drying-out, a saltier root zone, and fewer, larger waterings. Even a mild, deliberate water deficit applied at the right time shifts a cannabis plant generatively without losing yield.^[1]

The system runs in two cooperating layers. A Home Assistant integration gives you every on-screen control and reading. An AppDaemon engine (master_crop_steering_app.py) is the decision-making brain that fires the shots. The room is wired as 3 rows (zones), each with its own moisture and salt probe and its own valve, all fed from one shared tank, one pump, and one main line.

Accuracy, self-review, and grain-of-salt notes

Key terms, defined

Three measurements run the whole system. Learn these first. Everything else builds on them.

The P0–P3 daily cycle

Each row moves through four phases across the lights-on day, driven by the light schedule (defaults: lights on 10:00, off 22:00). The rhythm is always the same. Dry a little, refill, maintain, then wind down for the night.

• P0 (morning dryback): after lights-on the system waters nothing and lets the medium dry a small amount (p0_dryback_drop_percent, e.g. 5–10%). Exits to P1 when that target is hit OR when p0_maximum_wait_time expires (default 120 min).
• P1 (ramp-up): shots start at p1_initial_shot_size, grow by p1_shot_size_increment, are capped at p1_maximum_shot_size, spaced by p1_time_between_shots, and bounded by min/max shot counts. Exits when VWC ≥ p1_target_vwc.
• P2 (maintenance): the bulk of the day. Waters whenever VWC drops below p2_vwc_threshold; if the EC ratio runs above ~1.2 it waters MORE (to dilute), below ~0.8 it holds back.
• P3 (overnight): normal irrigation stops a set number of minutes before lights-off (p3_veg_last_irrigation / _gen_); only emergency top-ups fire below p3_emergency_vwc_threshold. Zones hold P3 all night.

The two steering modes pick which targets the engine chases. Vegetative means high VWC, modest dryback (~10–20%), lower EC (~3.0 mS/cm), many small shots. Generative means lower VWC, bigger dryback (~25–50%), higher EC (~4.5–6.0 mS/cm), fewer larger shots. Set the mode globally with select.crop_steering_steering_mode or per row. A row override beats the global, and ‘Follow Main’ means use the global.

The controls and targets that matter

Day to day you touch a handful of controls. Two arm switches set how ‘on’ the system is. System enabled is the master arm. OFF means nothing irrigates ever, and the engine fails safe to OFF if it cannot read the switch. Auto irrigation only governs engine-driven shots. Turning it OFF still lets manual shots through, which is how you run ‘watch mode.’

The targets that steer growth are the per-phase VWC numbers (p1_target_vwc, p2_vwc_threshold), the dryback targets, and the per-phase and per-mode EC targets (ec_target_veg_p0..p3 and ec_target_gen_p0..p3). Per-row selects let you push one row generative while the others stay veg, set who waters first when only one row can fire, and group zones to coordinate them.

• EC stacking switch ON lets the engine raise root-zone EC by reducing water, a generative push. Usually OFF for veg.
• Hardware you can see: the pump (Tuya plug, ~490 W running), the main-line relay, and switch.f2_row1/2/3 zone valves. Only one waters at a time.
• Per-row selects: steering_mode, crop_profile (Follow Main + 7 profiles), group (A–D), and priority (Critical / High / Normal / Low).
• Shot duration is computed from substrate_volume, dripper_flow_rate, drippers_per_plant and shot size %. Set these correctly or every shot is the wrong size.
• Per-row safety caps: max_daily_volume (L), shot_size_multiplier, and plant_count.

How a single irrigation decision is made (the gates)

When the engine decides a shot is needed, that shot only fires if it passes every safety gate in order. A single failed gate blocks it. This is what stops an autonomous system making a bad call.

• Order: system armed → auto-irrigation (manual bypasses) → zone enabled → no manual override → not dosing → tank not empty → source pH/EC in range (default pH 5.8–6.2) → safety limits (daily-volume cap, max-EC ceiling, max-frequency).
• pH/EC out of range blocks the shot and sends a phone alert with an ‘Irrigate Anyway’ button.
• Tank guard blocks only when the low float reads empty, so the system can keep watering as the tank drains down.

Calibration: getting the numbers right before you trust it

Calibration is the most important practical step. The system only behaves correctly if its number entities match your actual medium. The factory defaults are placeholders (50% VWC / 50% dryback), not your substrate. Dielectric moisture probes read differently in every medium, so a substrate-specific calibration is what makes the numbers mean anything.^[2]

1. 1
   Observe

   Hand-water normally for a few days and watch each row's VWC. The reading just after watering is roughly field capacity (the peak). The reading just before the next watering is the trough. Together they define that row's operating band.
2. 2
   Set the band

   Set field_capacity just above the highest peak, p1_target_vwc to each row's post-water peak, and p2_vwc_threshold a few percent below that. A smaller gap means a tighter veg band.
3. 3
   Set the drybacks

   Veg ~15–20%, gen ~25–45%. p0_dryback_drop_percent 5–15%. Set the emergency floor a few percent below the normal trough.
4. 4
   Set EC targets

   Slightly above feed EC for veg, well above for generative. p2_ec_high/low_threshold are multipliers on target (1.2 dilutes above 120%, 0.8 conserves below 80%).
5. 5
   Run and refine

   Let it run a few cycles in watch mode, compare predicted against actual, and tighten the numbers.

Root growth itself changes how the probe reads over a run, so re-check the band occasionally rather than calibrating once and forgetting it.^[4]

How-to recipes for common jobs

Most routine actions have a safe, prescribed method. Prefer the integration services over raw switch-flipping. The services run the full gated hardware sequence so you cannot skip a safety check by accident.

Safety fail-safes, emergency stop, and troubleshooting

The system has layered fail-safes: the pH/EC source-water gate, a tank dry-run guard (blocks only when the low float reads empty), a blocked-dripper guard that parks a row for 2 hours after too many failed shots, fail-safe reads (an unconfirmed arm switch is treated as disabled), and persistent state saved every 5 minutes so zones come back in their saved phase after a restart.

1. 1
   Fix the root cause

   Sort the physical problem first: empty tank, kinked line, bad probe, blocked dripper.
2. 2
   Confirm hardware off

   Verify pump, main line and all valves read off.
3. 3
   Check engine arm state

   Look at System enabled and Auto irrigation before re-arming.
4. 4
   Re-arm and sanity-check

   Re-arm, then read sensor.crop_steering_current_phase for the live phase.
5. 5
   Watch one cycle

   Do not walk away. Watch a full cycle fire correctly before trusting it again.

Realistic expectations

Treat F2 like a sharp tool, not an oracle. Watching is a discipline worth keeping. Tracking your numbers over time the way a process-control chart does lets you tell a real signal from ordinary noise before you act on it.^[5] For the cultivation theory behind the dryback and EC levers, read the coco crop steering paper. To understand the probes the whole system trusts, read root-zone sensing next.