Soil moisture sensor (Watermark)

Product info

This soil moisture sensor consists of three Watermark sensors, an NTC temperature sensor and a Crodeon Watermark adapter with M12 cable. This combination allows you to measure soil moisture at different heights or in different locations for increased accuracy.

The Watermark adapter by Crodeon is a small electronic sensor adapter that reads and calibrates three Watermark sensors with an NTC soil temperature sensor using the formula developed by Dr. Clinton C. Shock in 1998.

The Watermark adapter uses high quality pseudo-AC excitation as specified by the manufacturer Irrometer (source: www.irrometer.com/200ss.html) to extend the life of the sensor and optimize the accuracy of the readings.

The readings of the Watermark are expressed in kilopascals. A higher reading means the soil is dry and plants therefore have to make more effort to extract water from the soil. Use the following readings as a general guideline:

• 0-10 kPa: Saturated soil
• 10-30 kPa: Soil is adequately wet (except coarse sands, which are beginning to lose water)
• 30-60 kPa: Usual range for irrigation (most soils)
• 60-100 kPa: Usual range for irrigation in heavy clay
• 100-200 kPa: Soil is becoming dangerously dry for maximum production. Proceed with caution!

The Reporter reads the calibrated soil moisture and soil temperature values in real-time using a waterproof M12 cable. This means only one connector on your Reporter is used to read 3 Watermarks and 1 soil temperature sensor.

The M12 cable can be extended up to 30m using M12 extension cords. Multiple Watermark adapters can be plugged into one Reporter or combined with other sensors in our shop. The Watermark adapter is designed for low power consumption so it can perfectly work with your solar powered Reporter.

Patented Watermark sensor

Over the last four decades, the Watermark soil moisture sensor has been the preferred choice of growers, irrigation experts and researchers alike for providing the most affordable, simple and reliable measurement of available soil water.

The Watermark soil moisture sensor acts as an artificial root, exchanging water with the surrounding soil as a plant does. This exchange enables measurement of how much effort (suction or soil water tension) is required by a plant to extract water that is available from the soil, not just what the moisture percentage of the soil may be. Measuring this soil water tension provides reliable data for irrigation scheduling, without requiring complicated calibrations for individual sites and different soils.

Comparing the Watermark sensor to the SM100

Both the Waterscout SM100 and the Watermark sensor measure soil moisture. However, there are some differences that we can point out. The SM100 measures the soil moisture content as a percentage of the soil volume, whereas the Watermark sensor actually measures how much effort is required by a plant to extract water that is available from the soil.

For a full comparison between these sensors, read our blog post on this topic.

Installation

Before installing the sensors, make sure to follow this procedure in order to improve the sensor response in the first few irrigations.

Soak the sensors overnight in irrigation water. Always install a wet sensor. If time permits, slowly wet the sensor by partially submerging (no more than half way) for 30 minutes in the morning and let dry until evening, wet for 30 minutes, let dry overnight, wet again for 30 minutes the next morning and let dry until evening. Soak over the next night and install wet. This will improve the sensor response in the first few irrigations. 

If the Watermark sensors are mounted on a pvc pipe, make sure the hole you're drilling in the ground has the same diameter as the pipe (not larger).

For more detailed instructions about using and maintaining the Watermark sensor, please refer to the documentation from the manufacturer: Download manual.

Physical properties