Going Deep on Soil Moisture Sensors: Why Your Farm Needs Them & How to Choose a Probe

Gill Costa MBA/CCA

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Farmers that irrigate crops are now at a crossroad given the multitude of crop production challenges, requiring accurate estimates from soil moisture sensors.

Some of the biggest challenges are:

• increase in competition and prices for water resources with municipalities and industry that usually have the upper hand given the economic weight and demographic representation;
• increase in energy costs for pumping and conveyance;
• and finally regulations that restrict water resources availability.

With the aforementioned adversities, farmers understand that to maintain their economic and environmentally sustainable operations the accurate and judicious use of irrigation water requires a high level of precision in irrigation management, making soil moisture monitoring indispensable.

This provides us with the insight of the urgent need for soil moisture sensors in every irrigated field and a clear and tangible return on investment to implement soil moisture monitoring technology.

Soil Moisture Sensors tell you when to turn irrigation on & how long to let it run

Soil moisture sensors reveal the correct time to start irrigation and stop irrigation. Reviewing 2 main irrigation management terms will allow for a better understanding of irrigation thresholds;

• Field capacity is the amount of soil moisture held in the soil in equilibrium with its texture water holding capacity after excess water has drained away. (turn irrigation off )
• Onset of stress the minimum amount of water in the soil that the plant requires not to close stomata and start impacting crop productivity. When the soil water content decreases any lower crop productivity is reduced. (turn irrigation on)

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From the above definitions, we are able to conclude that irrigation must start at the onset of stress point and stop at field capacity point, as detailed in the water holding capacity by soil type above. The duration of irrigation will be based on crop root zone depth, soil hydraulic conductivity, soil water holding capacity, and crop physiological demand, usually guided by soil moisture sensor data. From the above variables a concise software interface layout in Verdi’s software irrigation management platform a farmer can efficiently and accurately manage irrigation for maximum crop productivity.

Understanding Soil Moisture Sensors and Probes

Soil moisture sensors measure moisture at a single point in the soil and are generally used for shallow-rooted, annual crops. They are typically handheld, portable devices that offer localized moisture data near the soil’s surface. On the other hand, soil moisture probes have multiple sensors and are designed for deep-rooted, perennial crops. The soil profile probes house multiple sensors that can measure moisture at various depths, making them ideal for permanent installation in perennial crops like trees and vines.

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Farmers can choose from over 10 brands in the market to collect soil moisture data based on the crop, economic resources, and farmers irrigation management objectives.

How to choose the correct soil moisture sensors for each crop?

After reviewing the soil moisture sensor technology options a farmer should understand that sensors that provide the volumetric water content unit output allows for a more precise irrigation scheduling. This is because the unit of volumetric water content can be easily interchangeable with actual inches or millimeters of water in the soil that enables accuracy in inches or mm to be irrigated.

Further VWC as percent  provides information to prescribe irrigation cycles with better accuracy to replenish the rootzone without wasting water, energy and nutrients leaching past the rootzone. Therefore, choosing a sensor with % VWC units is preferable for irrigation scheduling and management, ensuring accuracy in irrigation management.

The other parameter to consider inchoosing a soil moisture sensor is the type of crop and rootzone depth to determine the length of the soil moisture probes.Where single point soil moisture sensors are used for shallow roots, mostly onannual crops. While soil profile multisensor soil moisture probes are used for monitoring deeproots, mostly on trees and vines, measuring soil moisture at various depths.

Finally a farmer should choose a soil moisture sensor that delivers volumetric water content as percent being that frequency domain reflectometry (FDR) is the most reliable technology to measure soil moisture in volumetric water content as percent. In a final review, farmers should choose a soil moisture sensor with the FDR frequency domain reflectometry technology reporting VWC as a percent.

Being that a single point sensors are used for annualshallow root crops, andmeasures soil moisture levels effectively in the active rootzone. Whereas a deep and longsoil profile multi sensor probe that collects data from 60 cm - 2 ft  downto 120cm-4ft is recommended for perennial crops like trees and vines.

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How Can I Get Accurate Soil Moisture Sensor Data?

Where the average accuracy from most manufacturers is (3%) volumetric water content (VWC). For agricultural applications the value of soil moisture monitoring comes from the real time graph trend analytics that reveals the overall plant water use physiology and not from one point measurement in time (% VWC) accuracy.

Remembering that over 90% of all water used by plants is for thermal regulation and around 10% for actual metabolic use. Making it clear that graph trend dynamics interpretation from real time continuous data collection from plant consumptive use is the most valuable information for irrigation management decisions.

Current limitations in deploying soil moisture monitoring.

There are many companies in the market that currently offer solutions that are priced out for many farmers with entry monitoring units starting at USD$ 3000. In addition the lack of agronomical support to effectively implement irrigation management strategies based on soil moisture data. With these typical frustrations and setbacks we can identify market trends such as in the fresh produce industry where soil moisture sensors are only adopted by 25% of the farmers. That is why Verdi is coming to the market with the most affordable and scalable soil moisture monitoring platform in the market. In addition to agronomists on demand for live webinars to answer any questions. Feel free to schedule a meeting below with an agronomist.

‍https://calendly.com/d/cpjx-9y2-hyd/verdi-free-consultation?month=2024-09

How does a farmer implement soil moisture monitoring?

Soil moisture monitoring for irrigation management is implemented with the installation of soil moisture sensors in a representative part of the field, telemetry communication equipment transmitting real time data into an online platform. Soil moisture monitoring technology has become essential for irrigation management.

With this critical need for soil moisture data in mind Verdi is launching all of the parts needed to implement wireless soil moisture monitoring into a simple-to-install packaged product, without needing to run miles of messy cables. From Verdi’s online webstore a farmer can order either a row crop soil moisture monitoring package and or a tree and vine soil moisture monitoring package.

The Verdi package can be easily ordered online with a few clicks and ready to be deployed in your fields within a few days. The practical self explanatory installation process using QR codes for deployment allows farmers to get soil moisture data within 15 minutes. In addition Verdi’s agronomic support is available to help farmers make the best use of this technology.

Order Verdi latest soil moisture monitoring package below.

https://e9d5d2-f8.myshopify.com/products/smart-kit-for-soil-moisture-single-depth

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