How to Use Soil Moisture Sensors to Make a Monitoring Strategy that Maximizes Yield and ROI on Agricultural Irrigation Systems
Gill Costa MBA/CCA
In this article the Verdi blog team has the objective to introduce the basics of irrigation management by direct soil moisture monitoring. By the end of this article, you’ll understand enough about soil moisture monitoring to create a basic strategy for your farm. You’ll learn:
- Why soil moisture monitoring is important
- Where you need to monitor
- What most farmers get wrong
- How to measure soil moisture
- Important links for understanding measurements
- How to improve your crop using soil moisture measurements.
Why Soil Moisture Monitoring is Important to Farmers
Water management has become a key production variable that can determine the success of an agricultural operation. Over-watering crops can cause disease outbreaks, nutrient losses, and overall inefficient use of water and energy resources. Under-watering crops results in low yield. and vigor. Soil moisture monitoring is a critical feedback mechanism for optimization of irrigation management.
1) Defining your irrigation block boundaries
Irrigation management involves principles from the establishment of irrigation field boundaries. Where the delineation of an irrigation block should have soils that are uniform in soil texture, and water holding capacity. With this approach an irrigation block is able to be irrigated with uniformity in infiltration rates, and even wet and dry out cycles.
This allows irrigation managers to achieve water distribution uniformity, outstanding yields, water use efficiency, optimum nutrient uptake and overall achieving optimum yields with good agricultural practices sustainably.
The reality of how farmers actually build irrigation blocks
However in reality uniform soil irrigation blocks only occur in unique class A soils of prime farmland that are becoming more and more expensive. In general 90% of irrigation blocks will be delineated by 2 or more soil types and textures that managed under 1 irrigation block without addressing the differences in water holding capacity portions of the field with suffer with over or under irrigation that results in lower yields , disease outbreaks and the inefficient use of water and energy resources.
2) Determine Your Water Holding Capacity Through Indirect or Direct Methods
The second step in creating a soil moisture monitoring strategy after delineating soil types is determining soil water holding capacity.
There are two main options to determine irrigation block soil water holding capacity being either direct by soil sampling and indirect by using a soil survey map.
Soil Sampling
In the direct method a soil sample is collected and submitted to a lab that will provide a particle size distribution analysis revealing in situ field capacity and wilting point.
Soil Survey Mapping
The indirect method to determine soil water holding capacity is done by consulting a soils map of the field.
If your farm is located in the USA, consider yourself lucky because there are free resources already prepared for you.
- The map will reveal the sand and clay content (https://casoilresource.lawr.ucdavis.edu/soilweb-apps).
- Once the soil approximate texture is determined from the clay and sand content the numbers need to be entered into the SPAW Hydrology tool - Soil Water Characteristics(https://www.nrcs.usda.gov/resources/tech-tools/spaw-version-602).
- After entering the clay and sand content the software will provide the approximate soil water holding capacity parameters such as field capacity and wilting point.
3) Establish Irrigation Threshholds for Your Crop
Once one of the two mentioned methods of determining field capacity and wilting point are established, an irrigation manager is able to determine volumetric water content thresholds to start and stop irrigation.
The thresholds of starting and stopping irrigation will be based on a crops specific maximum allowable depletion. Next by subtracting field capacity from the wilting point the total available water is revealed. Next step is to multiply total available water by the crops maximum allowable depletion which the result is the plant available water. And finally by subtracting field capacity from the plant available water the point of opening irrigation is determined which is the onset of stress.
The point of turning the irrigation off once the rootzone is replenished will be field capacity. With the understanding that irrigation must be turned off at field capacity where over watering can cause disease outbreaks, nutrient losses, and overall inefficient use of water and energy resources.
A full breakdown of calculations in this step can be found here:
https://www.fao.org/4/x0490e/x0490e0e.htm
4) Sensor Installation to Manage Irrigation Based on Soil Water Content
The final step of soil moisture monitoring after determining the irrigation thresholds of the crop is to install a soil moisture sensor. Soil moisture sensors can be divided into 2 categories being single point sensors used on annual crops and multi sensors packaged in soil probe used for monitoring deeper roots in perennial crops.
When installing a soil moisture sensor a representative area of the field must be chosen usually 2/3 down the row away from the main water line source. The sensor needs to be installed in the active root zone offset from the water emitter. This allows the farmer to monitor the part of the field with the most restrictive water delivery.
Verdi is able to fix bad irrigation block design in older irrigation systems
This is where Verdi’s innovation latest solution is able to address inherent limitations on irrigation block design with the latest Micro Row Block Controller. The Micro Block Controller is able to manage irrigation cycles row by row allowing managers to adjust irrigation precisely for zones with different soil water holding capacity and different irrigation run times to match crop demand.
There are no limits to precision irrigation with the right technology
Verdi has developed the latest SDI-12 integration to multiple brands of soil moisture sensors. With Verdi’s technology an RTU transmits soil moisture data to the Verdi main Gateway that uploads the data into Verdi software that provides online real time data and graph software for irrigation managers to make precise irrigation decisions.
Where the Verdi system has the capacity to connect up to 200 devices reporting online. Verdi also developed the simple and affordable soil moisture monitoring packages that farmers can easily order and deploy with a few simple steps and have online data instantly.
Further the Verdi monitoring platform will enable a grower to receive alerts when to start and stop irrigation. With this information a farmer can make accurate irrigation decisions on irrigation duration and frequency.
Additionally Verdi automation solutions delivers the complete solution for remote irrigation automation to open and close valves remotely, start and stop pumps, detect leaks and breaks. In which Verdi automation solutions can seamlessly upgrade existing irrigation systems to execute precise irrigation cycles achieving outstanding yields with water and resource use efficiency.
