Matching Soil Moisture Profiles - Minirhizotron & Diviner 2000

Diviner 2000, a portable and rugged instrument, provides a convenient solution for measuring soil moisture levels at multiple locations throughout the soil profile at 10 cm intervals. Equipped with a manual FDR probe, it performs soil profile measurements in a matter of seconds in access tubes down to 160 cm. With the ability to monitor many locations, this affordable manual unit comes with a handheld data logging and display unit -  ready for easy field use. Suitable for a wide range of applications including irrigated crops, arboriculture, environmental and landscape management including urban greening, and research projects, the Diviner 2000 is versatile and highly flexible. It is a perfect companion to manual manual minirhizotron imaging campaigns, allowing depth-matched soil moisture profiles to be related to the root dynamics observed during mini-rhizotron studies.

• Measurement is quick, easy, and reliable
• Ideal solution for measuring multiple sites, making it a valuable tool for research and environmental monitoring in situations where permanent probes cannot be installed (e.g. urban environments). Ideal to combine with manual root imaging in MR tubes.
• Automatic depth detection, supports up to 16 depths (probe available in 0.7, 1.0, and 1.6 m lengths); stores data from multiple-sites (up to 99 locations)
• Universal calibration works over a range of soil types or select a matching soil from the available library; built-in probe orientation feature improves repeatability; soil type & management specific calibrations have been developed for a range of use cases (see references below)
• Easy data access via the large, backlit handheld LCD display (with graphical and tabular data displays to facilitate immediate management decisions). The IrriMAX software can be used to visualize soil moisture patterns. Download data in tabular form for in-depths data analysis (Excel to R).
• Provides a low-cost entry-level option for users; each site can be easily upgraded to continuous monitoring by using the access tubes with an EnviroSCAN probe. Allows results from continuously monitored access tubes to be compared with results from many additional "Diviner 2000"-locations.

The Diviner 2000 probe model is based on frequency domain reflectometry (FDR). This model consisted of a data logger connected to a probe by cable, allowing to take readings at 0.10 m intervals. Each reading is stored in the data logger for a fixed duration of 1 s and operated in the frequency range of 120,000 MHz (water) to 160,000 MHz (air), depending on soil water content.

To ensure most accurate measurements, it is necessary to normalize the equipment due to variations between different probes. This normalization procedure involved recording readings within a PVC tube (see Figure) that is separately exposed to air and water. The data output from the data logger is referred to as the scaled frequency (SF), which is calculated using the following equation (Eq 1):

(Eq1 ) F = (Fa - Fs) / (Fa - Fw)

Here, Fa represents the frequency reading obtained when the PVC pipe is fully suspended in air, Fs represents the frequency reading obtained when the PVC pipe isinserted into the soil, and Fw represents the frequency reading obtained when the PVC pipe is immersed in water.

Due to the inherent limitations in accurately determining relative frequency (SF) readings based on soil texture, the manufacturer recommends that exponential calibration be applied to the equipment used to measure relative frequency as well as soil volumetric moisture. See the calibration manual (pdf) below to calibrate the Diviner 2000 to your soil and land use type, using soil ring samplers to determine the gravimetric soil moisture (replicated) along the Diviner depth profile (using a profile wall / trench method), or vertical soil coring with low compression.