Smart fertigation is moving from timers to sensors, with EC, pH, and ORP probes driving pumps in real time. Trials report 30–40% fertilizer cuts, 20–60% water savings, and higher yields as automated systems “dose to target.”
Modern fertigation and chemigation are starting to look a lot like process control. In-line sensors measure the irrigation stream and controllers adjust injection on the fly — a closed-loop approach that’s displacing timer-based routines. Analysts peg automatic fertigation system growth at roughly 8% annually from 2023–2032 (dataintelo.com), while Asia-Pacific’s on-field sensor market is projected to nearly double (US$0.88G to $1.8G, 2025–30) at about 15.4% CAGR (www.mordorintelligence.com).
In Indonesia, agricultural agencies are pushing automation for urban and commercial farms, noting it “enables plants to be nourished precisely in time, amount, and strength” (www.pertanian.go.id). The pitch is simple: less manual mixing, more consistent dosing.
In-line sensor basics and setpoints
In-line sensors sit in the irrigation line and stream live readings to a controller. EC (electrical conductivity) gauges total salts as a proxy for nutrient concentration; pH reads acidity/alkalinity; ORP (oxidation-reduction potential) tracks oxidant strength for sanitation in chemigation. Greenhouse operators routinely use in-line ORP to control chlorine dioxide or ozone: high ORP (≈650–800 mV) indicates strong sanitization and can trigger pump shutoff (www.greenhousemag.com).
Typical dosing cabinets pair two EC/pH probes in a bypass flow cell with an optional ORP probe, all wired to a logic controller. The controller reads 4–20 mA signals (a standard industrial analog current loop) from the probes and varies acid and fertilizer injection in real time. Technical guides note that EC can be used to calibrate injectors: mixing a known fertilizer dose in water yields a target EC, then the in-line sensor is adjusted to that value to lock in concentration accuracy (greenhouse-management.com).
Automated dosing control logic
Closed-loop systems couple probes to injector hardware: when EC drops below a setpoint, controllers open fertilizer injection; if EC runs high, they slow it. A pH probe drives acid/base addition, while an ORP probe modulates disinfectant flow to maintain a target band (for chlorine, around 650 mV in practice) (www.greenhousemag.com). Controllers — commercial or custom PLC/Arduino-based — can log readings and send alerts via Wi‑Fi or cellular. These smart rigs effectively “dose to target” (rather than “rate to time”), absorbing shifts in source water quality or pump wear.
Where chemical injection is specified, growers lean on accurate dosing pumps for fertilizer, acid, or sanitizer; in chlorine programs, ORP control can also be paired with on‑site generation via electrochlorination if desired for safety, while keeping the ORP signal as the process variable.
Yield, water, and fertilizer outcomes
The payoffs are quantifiable. In sensor-enabled greenhouse trials, irrigated strawberry yields ran 2–3× higher under sensor-based fertigation versus unregulated timer-based scheduling (www.frontiersin.org). Another trial reported automated fertigation used about 66% less water for Cucumis (melon) seedling irrigation while achieving the same plant growth as manual watering (www.researchgate.net).
Quality held: in sensor-driven soilless culture, yields were maximized with only minor (≈7%) drops in marketable harvest under fixed scheduling (www.mdpi.com). In a separate soilless strawberry study, a “smart” strategy cut fertilizer use by roughly 38% and irrigation water by about 26% versus a fixed timer schedule — and it achieved the highest yield (timer-based had ≈7% lower fruit mass) (www.mdpi.com).
Local programs echo that scale of benefit. IPB‑Indonesia’s Nutriferads automated fertigation system reports up to 30% savings in water and fertilizer, plus up to 40% higher plant productivity, with farmers’ workload down roughly 70–80% under automation (lpdp.kemenkeu.go.id).
In Spain, NutriBalance trials on citrus delivered the target blend within 7% of the ideal composition and cut fertilizer usage by about 40%, saving roughly €500 per hectare per year (www.frontiersin.org). Economically, NutriBalance reduced fertilizer costs by approximately 41–42% in young orchards (≈€340–500/ha‑yr) (www.frontiersin.org).
Hardware integration checklist
Core components for a retrofit: in-line EC/pH probes (and optional ORP) in a flow cell, injector hardware for fertilizer, acid, and sanitizer, and a controller. For open-field drip or pivots, metering pumps or controlled injectors allow fine rate control; low-pressure headworks can use Venturi or proportional-flow injectors with valve modulation. Sensors should sit downstream of the mixing/injector area but upstream of filters or emitters; many users mount probes in a bypass chamber for maintenance without draining.
Electrical integration is straightforward: probes typically output 4–20 mA or digital signals like Modbus (a common industrial communications protocol). Controllers (from hobby Arduinos up to industrial PLCs) read these inputs and switch injector pumps via relays or 0–10 V valve signals. Many farmers use commercial fertigation controllers (e.g., Bluelab, Atlas Scientific kits, or local brands) with setpoints and data logging; setup means configuring target EC and pH by crop stage.
Calibration, validation, and safety
Calibration routines matter. Before use, probes should be calibrated per manufacturer instructions with pH buffers and EC standards and then checked regularly (often monthly) to counter drift and fouling. It is good practice to verify injection accuracy by mixing a known nutrient dose and confirming the in-line EC matches the expected value (greenhouse-management.com). For ORP, around 700 mV correlates to about 2 mg/L Cl₂ in chlorine systems (www.greenhousemag.com). Backflow preventers are required by law in most jurisdictions.
Closed-loop dosing helps reduce overapplication risks. Indonesian research highlights that pesticide residues in irrigation runoff can harm waterways and human health (www.pertanian.go.id). Controlled chemigation (with ORP/pH feedback) minimizes excess agrochemicals entering soil water, and automation supports compliance by dosing accurately to label rates and by integrating required safeguards like backflow prevention.
Control software and commissioning
For each zone or crop, controllers hold EC and pH setpoints and alarm bands; some setups add weather or phenology (growth-stage) models as supervisory inputs. Alarms and notifications can shut injection if EC/pH drift outside limits and can be pushed remotely to a smartphone or PC. Commissioning works best at the turn of season: flush lines, dry-run with water to verify probe response, then introduce dilute fertilizer and acid progressively while logging how the system tracks setpoints.
Document source water quality by zone — if baseline EC is high, factor it into targets. For multi-parcel layouts, a central fertilizer tank can feed all zones (with solenoid valves selecting the field) or a separate pump can be assigned per zone.
Local retrofit example and telemetry
In tropical smallholdings, a practical configuration mounts a compact control box on an existing drip submain: a controller, an aquarium-grade dosing pump, and a digital pH/EC meter with probe in a bypass line. The pump draws from a 100 L fertilizer tank; during irrigation, the controller throttles the pump to hit the EC setpoint and injects pH correction as needed. Data are logged to an SD card or transmitted via a GSM module for off‑site analysis. Local startups (e.g., Fertigation Series IoT kits) show such integrations are feasible even for backyard greenhouses (www.taniin.id).
Economics and market signals
The economics are compelling. Saved inputs and labor often pay back sensors and pumps within a few seasons. At €500/ha savings (as above), even a $5,000 dosing rig would amortize over 5–10 ha. Globally, precision fertigation is projected to expand to a $6–7 billion market by 2030 (dataintelo.com), while Asia–Pacific farmers are investing heavily in in‑field sensors as the regional ag‑sensor market doubles by 2030 (www.mordorintelligence.com).
Bottom line and sources
In-line sensors plus automated dosing deliver data-driven irrigation fertilization. Studies and field programs show fertilizer cuts of roughly 30–40%, water savings of 20–60%, and yield lifts often in the double digits (www.mdpi.com; www.frontiersin.org). All cited findings are from 2018–2024 publications (lpdp.kemenkeu.go.id; www.frontiersin.org; www.mdpi.com; www.frontiersin.org; www.frontiersin.org; www.mordorintelligence.com; greenhouse-management.com; www.greenhousemag.com; www.pertanian.go.id).
