Field Service Report · Remediation
FSR-2090-0507 — Hydroponic Nutrient Blight Remediation
Diagnosis and correction of a nutrient blight presenting across a community deep-water-culture grow at the Pier-9 Hydroponic Co-op. Root cause traced to nutrient-solution imbalance and reservoir pH drift; corrected on-site per VC-SOP-0118 with a benign outcome.
Engagement classification. Benign GCL-1 remediation at a community partner site under goodwill service terms. Single-technician dispatch permitted (no two-person rule for GCL-1). Standard horticultural PPE only; no toxin, predation, or dispersal hazard present.
1. Site & Conditions
| Field | Entry |
|---|---|
| Site name / client | Pier-9 Hydroponic Co-op (community grow collective, goodwill referral) |
| Location / access | Repurposed wharf shed; 6 deep-water-culture (DWC) tables + 2 nutrient-film troughs. Open access during day hours. |
| Engagement type | Remediation |
| Ambient temp / RH | 21 °C / 68 %RH; reservoir temp 22.4 °C (high — see §4) |
| Conditions on arrival | Interveinal yellowing and marginal necrosis across leafy-green beds; lettuce and chard worst affected; root browning on two DWC tables. |
| Public proximity | Co-op members on-site; advised to hold off harvest until departure readings logged. |
2. Specimen Identification
| Field | Entry |
|---|---|
| Collection | Edible leafy-green hydroponic grow — 188 plant sites across 6 DWC tables + 2 NFT troughs |
| Accession scope | Member-owned heirloom and commodity cultivars; not Universal Flora stock. No UF- linkage. |
| Assessed GCL grade | GCL-1 (benign edible crop; no hazard to personnel) |
| Primary issues | (a) generalized nutrient blight — N/Fe/Mg co-deficiency masked by pH lockout; (b) root browning from warm, low-DO reservoir on tables 3 & 4 |
| Hazards | None to personnel; standard horticultural handling. |
3. Work Performed
- Walked all 8 grow lines with the PhytoSense handset; logged baseline CVI and Fv/Fm per bed group (Section 4).
- Drew reservoir samples from each table; measured pH, EC, and dissolved oxygen. Found pH 6.9 (vs 5.6–6.0 nominal) driving Fe/Mg lockout despite adequate stock concentration.
- Diagnosed the chlorosis as a pH-lockout nutrient blight rather than true depletion; EC confirmed solution was over-strength (2.4 mS/cm vs 1.4–1.8 target), compounding marginal burn.
- Performed a partial reservoir exchange (40%) on all tables to reset EC; re-dosed corrective nutrient blend per VC-SOP-0118 dilution table; titrated pH down to 5.8 with phosphoric corrector.
- Pruned necrotic foliage and excised browned root mass on tables 3 & 4; bagged and removed debris.
- Added a supplemental air-stone manifold to tables 3 & 4 to raise dissolved oxygen and arrest root browning.
- Briefed co-op members on daily pH/EC logging and a 24 °C reservoir-temp ceiling. Captured departure readings; CVI uplift already underway.
4. Readings Captured
| Metric | Unit | Nominal Band | Arrival | Departure |
|---|---|---|---|---|
| CVI — overall grow | % | ≥ 90 | 81.6 | 86.4 |
| CVI — tables 3 & 4 (worst) | % | ≥ 90 | 72.3 | 79.1 |
| Chlorophyll Fluorescence (Fv/Fm) | ratio | ≥ 0.78 | 0.71 | 0.75 |
| Reservoir pH | — | 5.6–6.0 | 6.9 | 5.8 |
| Solution EC | mS/cm | 1.4–1.8 | 2.4 | 1.6 |
| Dissolved Oxygen (tables 3 & 4) | mg/L | ≥ 6.0 | 4.1 | 7.2 |
| VOC / Toxin Index | ppb | < OEL | 0 | 0 |
Plant Sites Serviced1888 lines
Grow CVI86.4%▲ 4.8 pts on-site
Reservoir pH5.8corrected from 6.9
On-Site Time2.2 hroutine band
5. Parts & Consumables
| Item | Part / Lot | Qty | Notes |
|---|---|---|---|
| Corrective nutrient blend (leafy) | HL-NUT-LG-04 | 1.2 L | Per VC-SOP-0118 dilution |
| Phosphoric pH-down corrector | HL-PH-DN-02 | 0.18 L | Titrated to pH 5.8 |
| Supplemental air-stone manifold | HYD-AIR-6 | 2 | Tables 3 & 4, left on site |
| Disposal bags (plant debris) | BIO-BAG-1 | 3 | Necrotic foliage + root mass, non-hazard |
6. Containment Actions
- PPE: nitrile gloves, eye protection (GCL-1 horticultural standard)
- Containment method: N/A — in-place remediation, no specimen removed
- Two-person rule: N/A (GCL-1)
- Field dispersal control: N/A — no hazardous material
- Decon on egress: standard tool wipe-down; reservoir sample vials sealed for disposal
7. Outcome & Disposition
| Outcome | Resolved |
| Specimen disposition | All beds remediated in place and retained by the co-op. No removal. |
| Site left in condition | Grow stabilizing; EC and pH within band; members briefed on daily logging. |
| Emergency procedure triggered? | No. |
8. Follow-Up Actions
- Co-op to log daily pH/EC and hold reservoir temp ≤ 24 °C — owner: client — confirm by 2090-06-13.
- Remote CVI check via member-submitted PhytoSense reads at +14 d — owner: S. Aralia — due 2090-06-13.
- Log corrected reservoir baselines to partner metric record (metrics) — owner: S. Aralia — Done
9. Lessons Learned
Note. The blight presented as a multi-nutrient deficiency but the true upstream cause was pH lockout compounded by over-strength solution — adding nutrient would have worsened it. Recommend the GCL-1 hydroponic survey checklist (VC-SOP-0512) mandate a reservoir pH/EC read before any corrective dosing, to prevent mis-diagnosis. Minor; submitted as advisory only.
10. Signatures
| Role | Name | Date |
|---|---|---|
| Field Technician | S. Aralia | 2090-05-30 |
| Dispatch Lead | S. Aralia | 2090-05-31 |
| Client Representative | Steward, Pier-9 Co-op | 2090-05-30 |