Understanding Low Yields Through Geomatics

Making improvements to a field to boost its yield can be complicated and cost a fortune. Our digital soil-water prediagnosis highlights issues that are often difficult to spot with the naked eye, ensuring you invest in the right areas.

Just about every farm has one: a plot where yields fall short, no matter what measures are taken. Yet, one this is observed, it’s often difficult to determine with the naked eye what’s causing this lack of vigor: poor drainage, lower soil fertility, or a problematic soil structure?

Our new soil drainage pre-diagnostic service addresses this very issue. Drawing on our expertise in geomatics and agronomy, it reveals the likely links between water behavior on your fields and the vigor of your crops. In short, it provides you with insights to help you decide which investment in your land will be the most profitable.

At a time when input costs are rising, this could make a significant difference to your bottom line.

Indeed, “when nutrients are adequate for the crop, water management becomes the primary constraint on yield stability,” concludes a recent study reported in Le Bulletin des agriculteurs.

Cross-Referencing Various Data Sets

By using geographic information systems (GIS) to cross-reference data, our preliminary assessment goes beyond traditional soil drainage analyses.

“The prediagnosis first evaluates crop vigor using the NDVI,” explains agrologist Jean-Christophe Hébert, head of our agricultural engineering team’s grading services. Using images from the Sentinel-2 satellite, the NDVI indicates a field’s level of vigor.

“While it’s not a traditional yield map, it provides us with valuable insights we can work with,” says Jean-Christophe Hébert. “If a farmer tells us that crops aren’t growing well in a certain area, we can see it for ourselves.”

When available, the team also analyzes yield maps and spring aerial images. “Ideally, we analyze aerial images from different years to avoid misinterpretations based on a single, particularly dry year, for example,” explains the agrologist.

Elevation, Slope, and Depression Maps

The team then combines the NDVI with lidar data from the Ministry of Natural Resources and Forests. This data comes from an airplane that fires a laser beam toward the ground. The beam bounces back, and the time it takes to return to the airplane reveals the terrain’s elevations. “With the lidar data, we can calculate contour lines and slopes and see where water might accumulate,” explains the grading specialist.

This data is also used to calculate the Topographic Wetness Index (TWI). This index combines terrain topography and surface water. “All in all, it’s a runoff map,” explains Jean-Christophe Hébert. “The TWI shows where water flows, where it concentrates, and where it accumulates.”

Finally, our agricultural engineering team adds one last layer of data: IRDA’s soil maps. This allows the team to determine whether soil series are causing the differences in crop vigor observed in the NDVI or the spring aerial images.

In conclusion, this dataset does not provide ready-made answers. “Rather, it allows us to formulate hypotheses, suggest additional tests, and validate with greater confidence which corrective measures would be most appropriate,” says Mr. Hébert.

A Concrete Example: A Round-Plow Layout

Let’s take the example of a dairy farm that opted for a round-plow layout and drained its fields more than 30 years ago.

The NDVI shows some variability in crop vigor, particularly lower yields between the round plow furrows, in the drainage ditches. Topographic maps and the TWI confirm this observation: the drainage ditches do accumulate water, especially where there are minor slope irregularities.

Before suggesting that farmers should level their fields, however, the agrologist recommends conducting a few simple checks:

• Sample the biomass in the less vigorous areas to confirm whether this lack of vigor is actually affecting overall yield;
• Check whether drains installed more than 30 years ago are clogged, for example, by iron-rich ochre;
• Conduct soil profiles to determine whether soil type affects crop vigor.

Once these checks are complete, the farm will have all the information it needs to decide whether it should invest in improving its land and, if so, how.

When Every Plot Counts

With the rising cost of inputs, maximizing the productivity of each plot becomes particularly important. This is especially true when we don’t fully understand the variability in crop vigor or when we prioritize the barn over the field more often than not.

To improve your farmland, the expertise in geomatics, computer science, and agronomy combined in our preliminary soil drainage assessment may be just the tool you need!