Soil moisture makes yield, but how much do you know about your soil moisture levels? Metre-deep moisture probes combined with cellular communication are giving growers continuous updates on yield potential based on soil water, which can help with decisions on fertilizer top-dress, fungicide applications and marketing.

Crop Intelligence Moisture Probe in field

A probe of possibilities

Canola farmer Trevor Thompson
Trevor Thompson, who farms at Assiniboia, Sask., had three Crop Intelligence moisture probes on his farm in 2019. “With these probes, I’m taking out some of the uncertainty. Any time you can do that as a businessman, it’s huge.”

“Stored soil moisture is like money in the bank.”

Trevor Thompson, who farms at Assiniboia, Saskatchewan, uses this quote from well-known Saskatchewan soil scientist Les Henry to describe the value of his soil moisture probes.

Thompson had three probes on his farm in 2019, one in a wheat field and two in canola. The probes go one metre into the soil and have moisture sensors at 10, 20, 30, 50, 70 and 100 centimetre depths. Each probe and adjoining above-ground weather station provide Thompson with instant updates, including the crop’s water-driven yield potential (WDYP), through his phone. Complete stations, with moisture probes, are $3,000 to $4,000 each.

“With these probes, I’m taking out some of the uncertainty,” Thompson says. “Any time you can do that as a businessman, it’s huge.”

Soils in Thompson’s probed canola field hit the wilting point twice during the 2019 growing season because weather had been so dry up until the end of August. “This took the top off my yield,” he says. “We still got a very good crop, just not an excellent crop.” As a result, he didn’t top dress fertilizer or spray fungicide – which are two in-season decisions aided by a WDYP estimate.

Thompson’s probes and program are from South Country Equipment, a John Deere dealership with various locations in southern Saskatchewan. Ryan Hutchison, integrated solutions manager for South Country, has been involved with the company’s Crop Intelligence program from the beginning. The program is built around John Deere capacitance soil moisture probes. The probes were developed over 20 years ago, but it was at a farmer meeting in 2016 where Hutchison realized their potential value for canola in particular.

At the meeting, Hutchison and agronomist Kendall Gee, who was with Agri-Trend at the time and now works for Crop Intelligence, were sharing data from a soil moisture probe they were trying out in a few fields. “The probes were giving us data we’d never seen before in dryland agriculture,” Hutchison says. Elston Solberg, an Agri-Trend senior coach at the time, was at the same meeting. He looked at the numbers and did some math in his head. He then asked the group of farmers about their fertilizer rates and target yields. Most farmers in the area were fertilizing for 50 bu./ac. canola crops. Solberg then made a statement that changed everything: “Based on the probes results, you’ve got enough water to grow a 70 bu./ac. canola crop.”

“It was a real a-ha moment,” Hutchison says. “We came away from that day with a vow to proactively pursue the agronomy behind this data.”

They started working on algorithms based on water use efficiency for each soil type, each region and each crop, and developed the Crop Intelligence program to track ongoing changes in soil moisture and calculate real-time WDYP. With cellular communication from the in-field weather stations, it gave the farmer extra information for timely and informed in-season decisions.

Hutchison gives the example of one South Country customer who top-dressed nitrogen on a wheat field in 2019 based on the program data. The field had a WDYP of 24 bu./ac. above the farmer’s target yield. Because the farmer fertilized for the target, he realized, in time, that the crop would need more nitrogen in order to meet its WDYP.

Putting results in context

WDYP does not always translate into actual yield. It can’t. For Thompson, the canola yield in this probed field was about 12 bu./ac. below the program’s WDYP.

Gee says the program is based on water as the primary limiting factor. “Our numbers do not account for other factors that commonly reduce yield potential throughout the season,” she says. “Common factors, other than water, that affected Western Canada canola yields in 2019 were variable plant stands, flea beetle pressure, frost damage, hail, drought stress at key times and harvest losses.”

Thompson still found his 2019 results useful, though. “I might have wondered before, did I under-fertilize or was it Mother Nature?,” he says. “Turns out I needed Mother Nature to cooperate with more timely rains. I didn’t need to put down 40 lb./ac. more nitrogen.”

Crop Intelligence moisture graph
This is the Crop Intelligence moisture graph for one of Trevor Thompson’s canola fields in 2019. The red line is the water-driven yield potential (WDYP), which is given as a value above or below the yield goal. It was moving downward until timely rains in June. Click to open in full screen.

Real potential

Paul Bullock, soil scientist at the University of Manitoba, sees real potential for soil moisture probes.

“Since producers are starting to adopt farm-level soil moisture data, it is clear that they expect this information could benefit their farms,” Bullock says. “It should be a big help for decisions about mid-season nutrient and pesticide application.”

But, he adds, the challenge is how to make an accurate extrapolation about a field based on results from one probe.

Going forward, he sees the probes as part of an accurate and automated modelling system based on multiple inputs, including LIDAR for high resolution surface elevation, surface geology, groundwater pressure sensors, soil characteristics, precipitation, air temperature and evapotranspiration. These models, Bullock says, will distinguish soil moisture variation across a field without having to deploy hundreds of sensors. “This will make it more cost effective,” he says, adding. “There is a lot of work to do in order to make this information a reality, but I think it is feasible.”

Hutchison acknowledges these gaps and says they’re addressing them.
“We’re collaborating with CropPro and their SWATMAP system to collectively provide growers and agronomists further insights to the challenge of in-field variability,” he says. “I think we’re getting to this next stage.”

Meanwhile other companies have entered the space. Scott Speck is a digital ag lead for Farmers Edge, which has its own a network of field-based weather stations and soil moisture probes. The Farmers Edge crop modelling program predicts a crop’s stage and water balance, and how fast soil moisture will be depleted based on the crop stage and environment.

“Is the weather hot and dry with winds that would make the crop more prone to evaporation? Or is it cooler and humid, so the crop uses less water to reach equilibrium with the atmosphere?” Speck says. “Weather stations that are field centric help us identify these variables, and make conscious decisions on what to do next. This can be used to make decisions on fertility or fungicide if water supply is good and weather forecast is positive.”

As these programs evolve, Speck says data from multiple probes across a field, farm or network will also start to show us which tillage systems, soils, organic matter levels and slopes have the highest potential after rainfall events. The goal with all these models is to present farmers with simple tips, driven by lots of behind-the-scenes data and programming, to make better decisions.

Thompson is already seeing benefits for 2020. The Crop Intelligence program took his fall soil moisture measurements, which indicate a full moisture recharge, to estimate his canola WDYP for 2020.

“Having that information is huge,” Thompson says. “I have my fertilizer plan for 2020 all figured out based on that.”