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Ingredient

NPK soil probe (RS-485)

Also known as: 7-in-1 soil sensor, JXBS-3001, NPKPHT sensor

Industrial-style soil probe that combines nitrogen / phosphorus / potassium estimation with pH, EC, temperature, and moisture sensing in a single stainless-steel inserted spear. Communicates over Modbus-RTU via RS-485. The right ingredient when one buried sensor needs to give a complete agronomy reading at a fixed point — orchard fertility tracking, perennial-bed amendment scheduling, reference-bed monitoring. Hobbyist-grade Chinese probes ~$30–80 (JXBS-3001, RK520-02); the NPK readings are *indicative*, not laboratory-grade — true soil-nutrient assays still require lab analysis. Useful for relative trends and threshold alerts, not for absolute fertility recommendations.

Inputs / outputs

  • Power: 9–24V DC (most probes), ~50 mA
  • Interface: [[modbus-rs485|RS-485]], Modbus-RTU, default 9600 baud, address 0x01
  • Measurements: N (mg/kg estimate), P, K, pH, EC, temperature, moisture
  • Probe length: 60–150 mm typical

Solves / unlocks

  • Fixed-point fertility trend monitoring (relative changes are reliable even when absolute values aren’t)
  • Orchard-block fertility comparison (set up multiple probes, compare readings)
  • Threshold-driven amendment alerts (pH drift, EC spike, moisture out of range)
  • Long-deployment soil-condition logging
  • Reference-bed validation against laboratory soil tests

Constraints

  • NPK readings are estimates based on EC and conductivity-derived models; actual soil-nutrient values require lab assay.
  • Calibration drift — pH and EC readings drift over months; pull and recalibrate seasonally.
  • Soil-type dependence — readings are most reliable as relative trends within one soil type.
  • Power requirement — needs 12V supply; not a low-power sensor for solar nodes.

Source

  • JXBS-3001 (most common): generic Chinese vendors
  • RK520-02 (slightly higher-grade): Renke
  • Documentation often poor; Modbus register maps vary by vendor

See also

Auto-generated from this entry’s typed relations: frontmatter, grouped by relation type so the editorial signal isn’t flattened.

  • Member of: [[ingredient]]
  • Combines with: [[modbus-rs485]] · [[arduino-uno]] · [[esp32]] · [[home-assistant]]

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