Automatically Water Dry Spots in Your Lawn with a Soil Moisture Sensor

Dry or brown spots often appear in areas where a sprinkler system does not provide adequate coverage. An oscillating sprinkler connected to a garden hose can solve the problem, but it is easy to forget that the sprinkler is running and accidentally leave it on for hours.

This project uses a soil moisture sensor, a Wi-Fi controller, and a battery-powered sprinkler valve to automatically stop watering when the soil reaches the desired moisture level.

The Problem with Manually Watering Dry Spots

During the summer, portions of a lawn may turn brown because the existing sprinkler system does not provide even coverage. A simple solution is to place an oscillating sprinkler over the dry area and connect it to a garden hose.

The problem is remembering to turn it off. A forgotten sprinkler can run for several hours or even overnight, flooding the lawn and wasting both water and money.

Mechanical and electronic hose timers can limit watering time, but they still water according to a preset schedule. They do not know whether the soil actually needs more water.

A Soil-Moisture-Controlled Solution

Instead of watering for a fixed amount of time, this system measures the moisture level in the soil. The sprinkler runs while the soil is dry and automatically shuts off when the soil reaches the selected moisture level.

This approach allows the lawn to receive the water it needs without relying on someone to remember to turn off the hose.

Parts Used in This Project

  • Vegetronix VH400 soil moisture sensor to measure the moisture level in the lawn.
  • Vegetronix VegeHub Wi-Fi controller to read the sensor and control the sprinkler valve.
  • Latching sprinkler valve to turn the water supply on and off.
  • Oscillating hose sprinkler to water the dry portion of the lawn.
  • Hose adapters and plumbing fittings needed to connect the garden hose, valve, and sprinkler.

How the System Works

The VH400 soil moisture sensor is inserted into the area of the lawn that needs additional water. The sensor is connected to the VegeHub, which is configured to check the moisture reading every 10 seconds.

When the moisture reading indicates that the soil is dry, the VegeHub sends a pulse to the latching valve. The valve opens and water flows to the oscillating sprinkler.

As the sprinkler waters the lawn, moisture moves into the soil around the sensor. Once the reading reaches the selected wet threshold, the VegeHub sends another pulse to the valve and shuts off the water.

Testing the Moisture Control

Before installing the sensor in the lawn, the system can be tested using a glass of water.

  1. Leave the sensor dry and confirm that the sprinkler valve opens.
  2. Place the sensing portion of the VH400 into a glass of water.
  3. Wait for the VegeHub to take another moisture reading.
  4. Confirm that the controller recognizes the wet condition and closes the valve.
  5. Remove the sensor from the water and dry it off.
  6. Confirm that the controller detects the dry condition and opens the valve again.

Because the VegeHub in this example reads the sensor every 10 seconds, the valve responds within a few seconds of the moisture condition changing.

Installing the Sensor in the Lawn

After testing the system, insert the VH400 into the soil within the dry area of the lawn. The sensing portion should make good contact with the surrounding soil so that it can accurately detect changes in moisture.

Position the oscillating sprinkler so that it covers the brown area, then allow the system to water automatically. The sprinkler will continue running until the soil around the sensor reaches the configured moisture threshold.

Sensor placement is important. If the sensor is too close to the sprinkler, it may become wet before the surrounding lawn has received enough water. If it is too far outside the sprinkler pattern, the system may run longer than necessary.

Advantages of Watering by Soil Moisture

  • The sprinkler shuts off automatically when the soil is wet enough.
  • Watering is based on actual soil conditions rather than elapsed time.
  • The system reduces the risk of leaving a hose sprinkler running overnight.
  • A latching valve allows the system to operate efficiently from a battery.
  • The setup can provide supplemental watering to areas that are missed by an existing irrigation system.

Parts List

Add Hose Controller Parts to Cart

You can mount these to a 3/4" PVC post using these optional brackets:

Are you ready to get started with Vegetronix technology. Click on this button, and it will add all of the parts you need for this kit into your shopping cart. Afterward you can add, delete and substitute parts from your cart to create the perfect solution. You can also swap out cable lengths, if you need longer cables.

Final Thoughts

A hose sprinkler is an inexpensive way to correct dry spots in a lawn, but manually operating it can lead to over watering. Adding a soil moisture sensor and an automatic valve makes the sprinkler responsive to the actual condition of the soil.

Instead of guessing how long the sprinkler should run, the system waters until the lawn reaches the desired moisture level and then turns itself off.

VG-METER-200