Build Your Own Smart Fertigation System: Automate Irrigation and Nutrient Delivery

I've always sought a reliable irrigation controller for both home gardens and research projects, one that truly understands the complexities of agricultural systems. As a researcher, I've used numerous commercial systems, but they often fell short due to a lack of agricultural expertise in their design. Many manufacturers prioritize electronic and software engineering, overlooking the fundamental principles of agricultural systems.

Through years of experience, I've learned that a reliable automatic irrigation system requires four essential components:

1. Reliable Soil Moisture Signal: Accurate and consistent readings are paramount.

2. Dependable Controller: A robust and versatile control unit is crucial.

3. Intelligent Automatic Irrigation Scheduling Algorithm: A well-designed algorithm ensures optimal water usage.

4. Efficient Irrigation System: A reliable delivery system for water and nutrients.

Unfortunately, many commercial systems lack one or more of these components. This is why we developed our own irrigation control system, with a team combining expertise in electronics, computer science, and agriculture.

Calendar-based irrigation, relying solely on timers, often leads to water waste or inadequate irrigation. Integrating a reliable soil moisture sensor can significantly improve accuracy, but only if the sensor is of high quality. Many controllers limit compatibility to specific sensor brands, often not the best choices. Moreover, there are few, if any, commercial controllers that work with sensors optimized for soilless media like rockwool or coco coir and use a reliable irrigation scheduling algorithm.

We are proud that our SUMERIT automatic irrigation system addresses all four aspects mentioned above.

I previously published a blog post about a project from fifteen years ago, where our former research group (Irrigation & Drainage Research Group - IDRG) designed and built a proof-of-concept automatic drip irrigation system. That system irrigated up to four zones using small pumps in a water tank with a float valve, connected to tap water.

At that time, we focused on the number of irrigation zones rather than signal accuracy. Many manufacturers still prioritize increasing the number of zones. Our recent project, the SUMERIT irrigation controller, works with our APAS T1 moisture sensor (for soil and soilless media), emphasizing accuracy and reliability.

In this article, I will explain how to build a complete automatic fertigation system using the SUMERIT irrigation node and off-the-shelf components. We will focus on a home garden with raised beds, but the concept applies to other settings like grow rooms, greenhouses, and orchards.

List of Materials

• SUMERIT 2P-BLE irrigation node 

• APAS T1 moisture sensor 

• Centrifugal Submersible Water Pump

• Rechargeable Sealed Lead Acid Battery (12V)

• Solar Panel (10W)

• Solar Charge Controller

• Inline Switch (> 2A @ 12V)

• 12V to 5V Micro USB Converter (Optional)

• Outdoor Enclosure

• Large Plastic Storage Container

• Drip Irrigation Kit

Disclaimer: These products have worked well for me, but this is not an endorsement. Please research and find suitable alternatives. Ensure all replacements are compatible. If you have any doubts, leave a comment.

Assembling the Control Unit

The wiring diagram (see image below) is straightforward. Red is positive (voltage), and black is negative (ground). The SUMERIT control output works as a switch, without polarity.

Rated Voltage and Current

The solar panel, battery, and pump are all rated 12V. The solar charger is designed for this setup. The pump's rated current is 1.1A (13.2W), easily handled by the battery.

I added an inline switch for troubleshooting, which I strongly recommend. It's rated 2A and 12V.

Irrigation Controller

The SUMERIT control output comes from a relay, handling 60W (up to 2 A @ 30 VDC or ~40 VAC or lower). For safety, stay within 60% of this rating. For higher-powered pumps, use an appropriate relay board.

The SUMERIT controller is designed for accuracy and reliability, working with the APAS T1 sensor.

Control Panel

The SUMERIT node includes mounting hardware for tabletop or wall configurations. I placed it in an outdoor enclosure with the other components.

Optional 12V to 5V Converter

The SUMERIT node has a built-in Li-ion battery, lasting about 6 months on a charge. Any 100 mA @ 5.0 V micro USB charger can be used. I added a 12V to 5V converter to keep it charged continuously.

Soil Moisture Sensors

1. Two Sensor Ports for Variability

Inconsistent readings due to substrate non-uniformity and installation errors are common. The SUMERIT node averages readings from two sensors, improving accuracy.

2. Installing Sensors

Installation depends on the sensor, your needs, and the medium. Test readings after installation to ensure they are within an acceptable range. Refer to my previous blog articles for guidance.

I use vertical (top-down) and horizontal (trench/hole) installations. Refer to the APAS T1 user manual for more details.

Water Storage and Irrigation Pump

I upgraded to a 28-gallon container to accommodate my expanded garden. I plan to add support to prevent bulging.

Irrigation System

Drip or micro-sprinkler irrigation (see images below) is efficient, inexpensive, and low-maintenance. I recommend a similar system. Use a heat gun (not hot water) to soften tubing during assembly.

Irrigation Scheduling Algorithm and Controller Settings

The SUMERIT algorithm requires four parameters:

1. Dry Threshold (%): Triggers irrigation.

2. Start Time (Time of Day): Irrigation time.

3. Run Time (Minutes): Duration.

4. Moisture Sensor Feedback Type: One or both sensors.

Either the SHUSHAN Mobile app or SHUSHAN CVI Windows application can be used to set these parameters. Averaging readings from two sensors increases accuracy. If no sensor is selected, the system operates in timer-based mode.

Conclusion

This tutorial provides a detailed guide to building your automatic fertigation system. I will update this article over time. Please leave any questions in the comments below.