SWAT MAPS for Corn: Strategies for a Productive Growing Season

Amber Knaggs, BSc., PAg.
Regional Manager, MB

I love corn. It’s a crop that just has a lot going on. In Western Canada, it usually means you have a planter, invested in equipment and a dryer, and you are ready for the long growing season. And when that combine and corn header is finally parked, and you were lucky enough to complete the field work, you quickly move into planning season.

This means the “off season” or “winter planning” season is upon us. But this thinking that all the decisions are made during a few months of the year is not true. There are a handful of ‘aha’ moments throughout the growing season that seem to bring reminders of lessons not learnt. Or just a change of weather that highlights an issue that wasn’t previously apparent.

So, during this planning season of looking at the paperwork at your desk or on your screen and trying to plan for the best next season, remember the basics and what happened as your ‘aha’ moments. A soil test and a SWAT MAP can be an essential part of your planning. Below are a few corn related examples.

Salinity and Corn

Corn requires sufficient water. Salinity causes germination issues and poor growth. Soil salinity affects water availability to the corn crop, and any water stress to the corn affects its potential.

Table 1. Percent yield reduction due to salts. (NDSU Extension, 2019)

Table 1 illustrates the wide range of salinity and % yield reduction in corn. 2 mmhos/cm can reduce yield by 10%. However, at 4 mmhos/cm, that number potentially jumps to 50% yield reduction. And 5.5 mmhos/cm is potentially 100% yield reduction due to salts. This illustrates how it is not enough to know an area is just saline but leads to the question of “how saline is it?”.  Is your soil (or zone) a 2 mmhos/cm or is your soil a 4 mmhos/cm? Or are those poor areas 5.5 or more? Some fields are just not suitable for corn – we can’t VR the population enough to account for zones that won’t thrive - these areas should be planted to some other more tolerant crop. It is crucial to have the most detailed information to make that decision.

Don’t forget the micros!

Accurate fertility is essential for proper crop development, yield, and profitability. Having good soil test data to guide these decisions is important. Here are a few micronutrients to keep in mind for your ‘aha’ moments.

Cu by zone
Low copper availability is affected by low %OM, high pH, and highly correlated to soil textures. In the SWAT soil sample below, we see a trend where copper is lowest in Zone 1 and increases to Zone 10. A soil test value of less than 0.3 ppm, and low %OM would be a red flag that copper may be an issue.

Tissue testing is often used to complement information from soil tests. The Zone 1 tested below has  a tissue nutrient level for Cu of 2 ppm which indicates it’s in the nutrient deficient range. The DRIS index value is -101 which indicates this nutrient is most limiting. When both the nutrient level and DRIS index are low, it strengthens the confidence that this nutrient is deficient in the plant.

Micronutrient issues are often patchy, and it may be difficult to decide if you will get a response to applying a micronutrient treatment. Is the crop you are growing responsive or more sensitive to that nutrient? Is one of the other macronutrients more limiting? Or is there more of that nutrient at depth? If the soil is testing below a critical level, that usually means there is a higher chance of response. Sometimes you must live through an ‘aha’ moment, to know that something like a micronutrient is the issue.

Zn by zone
Critical levels of nutrients change by crop. A critical level for zinc of 0.4ppm may be suitable for wheat or barley crops, but with corn that critical level moves to 1.0ppm. Zinc is usually highly stratified with little found in subsoil. Eroded knolls that have lost a lot of topsoil, and accordingly zinc, are at a higher risk of deficiency, especially when pH is high as well. The SWAT MAP soil test shows low Zn levels in Zone 1 and increasing to Zone 10.

The complimentary tissue sample from the Zone 1, shows a deficient Zn nutrient level in crop and a -99 DRIS index value. These tests indicate Zinc is deficient in the plant tested.

Rarely does an entire field require a recommendation for a micronutrient treatment, making it a great fit for VR application. If most of the field is not testing below critical levels, apply only to the areas where it’s more likely you will have a response and ROI.

VR populations with a SWAT MAP

VR populations can be a large part of the planning process as covered in this blog Corn, soybeans, and the ultimate SWAT VR planting strategy. In the following example from 2024, a Southern Manitoba farm, created a VR rate for the entire field, then added strips of lower population of 26,000 seeds/acre, and a higher population of 36,000 seeds/acre.

Yield data was supplied by the client and analyzed by zone.

The data from this year, indicates that statistically, there were differences found between the lower 24,000 plants/acre population and the VR rate on most zones except zone 1. And then, for the higher 36,000 plants/acre population, only zones 3 and 4 were not significantly different than the VR rate. The VR rate corn population had the highest average yield.

I would challenge farms to work on trials that increase their potential agronomic and economic performance. Let’s plan on learning something new and not miss another entire growing season without trying different strategies. After all, you don’t want to be at this same planning stage next year, without having had a good ‘aha’ moment or two.

Make it a plan for any crop

Even if you don’t grow corn, many of these examples work for several crops throughout Western Canada, or anywhere else in the world. A SWAT MAP provides a lot of value and can be fundamental in your farm strategy during the season. Take this time to plan with your SWAT MAPS provider and keep moving forward.

Dabbling with VR lime and seeing the visual difference with Prairie Insights

Kyra Sinclair of Prairie Insights, located a mile north of Vermilion, AB, says harvest decisions are becoming easier and big ROI is more likely. Now in their fourth year of offering SWAT MAPS services to clients, the results continue to prove the visual difference seen in typically low yielding areas, and knowing that fertility isn’t being wasted.

“The main thing our customers are noticing is how even we’re managing their fields. In areas of their fields where they didn’t think it was possible to get that plant stand or that yield, we’re evening out that maturity,” said Sinclair.

Prairie insights began as an agronomic consulting and crop scouting business in 2018. After bringing SWAT MAPS into their business offerings, they now also specialize in zone soil and tissue sampling.

“We did lots of composite soil sampling and realized blanket applications need to be dialed down and we needed to be more specific about where we’re sampling. We wanted to offer farmers more intricate data. We found that relying on the data gives us a good picture of the field.”


In the area that surrounds Prairie Insights’ clientele, Sinclair says the low base saturation of calcium and acidic pH is a big limiting factor on yields. To combat this, they have been working with VR lime, which is new to the area.

“The cost of doing it may seem like a setback, but the maps help us save the producer money by not blanketing an application of expensive lime across the entire field. Sometimes only half of the field should be limed after we analyze the soil samples.”

Another hesitation is the worry of the difficulty level when it comes to using the technology and loading a map into the drill.


“Even customers who aren’t as techy are able to jump on board with this,” said Sinclair. “On the agronomic side there are producers who are skeptical too, but it all goes back to being able to see how even the crop is as it nears maturity and peace of mind knowing the money put into fertility isn’t being wasted.”

Prairie Insights is continuing to expand their horizons by focusing on liquid fertilizer applications through Y-drops on corn, exploring the use of SWAT CAM, and seeing great results with variable rate corn seed.

“We put so much passion behind what we do. We treat every field like it’s our own and we’re tweaking and perfecting all the time. We’re very proud of the retention with our clients.” said Sinclair. “At the end of the day we want our growers to put more bushels in the bins and if we can be a part of that then I believe we’ve done a good job.”

The SWAT MAPS Team is proud to work alongside dedicated teams like the one at Prairie Insights. Stay tuned with what’s happening in their area by following them on Instagram or contacting Kyra directly.

Instagram: @prairieinsights

Contact:
Kyra Sinclair
306-441-8084
kedwards@prairieinsights.com

Farmers: visit https://swatmaps.com/partner-locator/ to find a SWAT MAPS Service Provider near you.

Service providers: Contact us for partnership opportunities.

How Do I Choose the Right Variable Rate Program?

Chris Hawkins
Director of Sales – Farmer Services

In agriculture today where risk is high and profit margins can become quite thin, variable rate (VR) application programs have emerged as indispensable tools. They allow farmers to optimize input use, enhance crop yields, and maximize profitability, while at the same time minimizing environmental impact. However, with many VR programs and service providers available, farmers face the challenge of selecting the right system for their unique needs.

Here are some essential factors that farmers should consider before deciding on a VR program and service provider:

1. Establish Your Objective: There are many reasons why farmers utilize VR application. Increased yield, better pesticide application timing, and improved harvestability are just a few. Decide what problem you are attempting to solve with VR on your farm and find a service provider who will work with you to accomplish that.

2. Hardware Compatibility: Of course, you will need to make sure your own equipment is capable of, and ready to, apply VR prescriptions. Check with your equipment dealer on that. If it is “ready”, make sure your service provider can write prescriptions that will be compatible with your hardware because prescription files often need to be written specifically to match various types of controllers.

3. Field Variability (Zones): Many factors can influence variability within a field, and we have tools today to make field zone maps based on ALL of those factors at once (ie. satellite imagery, yield monitors, etc). Generally, these are a good view of “what” variability exists at a specific time (both spatial and temporal variability). However, great VR programs build zone maps based primarily on spatial factors such as soil, water dynamics, and topography (see figure 1). These stable characteristics are an ideal foundation for understanding “why” variability exists in any season.

Figure 1. SWAT MAP built primarily from spatial field characteristics.

    4. Ground Truthing and Zone Sampling: Make sure your service provider incorporates ground truthing when building the zone maps for your VR program. Ground truthing is the process of comparing what an agronomist sees in a field with their own eyes to the field data that was collected. In this way, the most accurate map possible is chosen as a template for soil sampling. A proper variable rate program includes soil analysis from the same points each year by zone so the agronomist can make precise recommendations based on nutrient changes from year to year.

    5. Scalability: Consider whether the VR service provider can scale with your operation as it grows. The best service providers are innovative and grow with you as they develop and incorporate new technology into their existing programs making their clients even more profitable. In figure 2 below you can see just one example of such technology. SWAT CAM can help to significantly reduce pesticide costs.

    Figure 2. SWAT CAM crop and weed imaging system. Photo: Croptimistic Technology Inc.

    6. Ease of Use: Development of a good variable rate program can be quite complex, however for the farmer, it should be relatively easy to use. The service provider should handle the complexity so you can focus on other aspects of your farm.

    7. Support and Training: Assess the level of support and training provided by the service provider to ensure successful implementation and troubleshooting. Support should be accessible especially in the peak seasons of work. The company should have both live people to speak with as well as online support.

    Figure 3. SWAT SUPPORT portal for learning and support.


    8. Cost/Benefit: When analysing cost/benefit of a variable rate program, look beyond just one year. Sometimes the upfront cost of VR systems may be higher in the first year, but significantly lower in the following years. Further to that, Return on Investment (ROI) is tricky to measure because it is farm specific. It's easy to look at yield alone because that's tangible. However, yield is influenced by many different factors so it should not be the sole measuring stick for the value of a VR program. There are other intrinsic benefits to consider, such as operational efficiency and grain quality. It's very difficult to measure the value of spraying your fungicide at just the right time, or minimizing lodging, but the value needs to be acknowledged.

    9. Reputation: Look for a system that offers high accuracy and precision in data collection, analysis, and application. Research the reputation and track record of the service provider, including their experience in the precision agriculture industry. Seek recommendations from other farmers or agricultural professionals to gain insights into their experiences with the system and service provider.

    10. Regulatory Compliance: Ensure the program complies with local regulations regarding pesticide and fertilizer application, data privacy, and environmental concerns.

      In conclusion, choosing the right variable rate program and service provider is an important decision that can significantly impact the success of your farm. By carefully considering factors such as map development and soil sampling process, scalability, ease of use, support and training, cost/benefit, reputation, and regulatory compliance, you can make informed choices that align with your goals and objectives.

      If you would like to learn more about our VR program which uses SWAT MAPS technology, or any of our new innovations (such as SWAT CAM), please connect with us at sales@swatmaps.com. Or you can find more information on our website at SWATMAPS.com.