Addressing Potassium Deficiency Using SWAT MAPS

Although the prairies are known for having the largest reserves of potash in the world, there are some areas with soils that have relatively low background potassium (K) levels — particularly in the black and dark grey soil zones of Canada that span northern Alberta, Saskatchewan and into Manitoba. In spring 2023, many of these areas are where we saw higher than normal temperatures coupled with humidity and adequate moisture. This created greenhouse-like growing conditions, making crops’ demand for nutrients high, resulting in more visual nutrient deficiencies than we might normally see, particularly K deficiency in cereal crops. 


There are many possible symptoms of K deficiency which can make diagnosis difficult. Looking at soil tests by SWAT zone combined with a comparative tissue test are often required to confirm deficiency. Symptoms include:

The most obvious and common deficiency symptom is yellowing of the oldest leaf that starts at the tip and progresses toward the base of the plant. These plants also tend to be stunted and have less biomass overall. Another common observation in fields displaying K deficiency is the presence of green, healthy strips where there was heavy straw or swaths —particularly in canola stubble — from previous years as K is the only nutrient that can be added directly back into the soil and is readily available by leaching through straw. 

Where to look

In the higher rainfall areas of the black and dark grey soil zones, soil K distribution tends to be predictable in relation to SWAT Zones. Soil K levels tend to be lower in upper landscape positions (zones 1-4) and higher in lower landscape positions (zones 7-10). SWAT Zones 1-4 generally have lighter soil texture and are water shedding, which allows for the movement of K down-slope. Potassium levels can also be correlated with soil texture, where higher clay content and cation exchange capacity means more K is held to soil particles and is less prone to leaching. These are soil characteristics more often seen in SWAT Zones 7-10. Given the generally higher annual rainfall in these regions, in many instances yields might be highest in zones 1-4 resulting in the greatest rates of nutrient removal.  

Table 1. K trend by SWAT zone in the grey soil zone of NE SK.

Field AreaOM %pHP (Olsen-P)KSClSalinity
Zone 1,2132.67.2171072750.12
Zone 3,4164.46.7814645120.23
Zone 5,6216.37.7101564580.26
Zone 7,8326.37.61623045240.34
Zone 9,10338.67.219252160211.01

K Stratification

Nutrient stratification is a naturally occurring process. Roots take up moisture and nutrients from below the soil surface and relocate them to above ground plant tissue to then be laid back on the soil surface when the plant’s life cycle is over. This process continues to happen in agriculture but is accentuated by some farming practices. Minimum or no-till fertilizer practices typically result in fertilizer being placed somewhere in the top 0-2” of the soil surface; however, plants are taking up nutrients throughout the soil profile which are returned to the soil surface in the form of straw. So, with relatively immobile nutrients such as phosphorus (P) and K, these nutrients continue to become very stratified in the top couple inches of soil (Table 2). Broadcast applications of P and K further accentuate this occurrence.

Table 2. Soil test P and K at varying depths and from a 0 to 8” test depth, from the Black Soil Zone of Saskatchewan.

Soil Test DepthP (Olsen-P, ppm)K (ppm)

In Figure 1, deficiency symptoms seemed to skip several seed rows in this field. This is the result of a few openers of the drill seeding shallower and seedlings accessing K that was likely stratified from previous years’ broadcast potash applications and from long-term no-till farming practices. K deficiency was confirmed through tissue testing healthy versus unhealthy rows of plants.  

Figure 1. Healthy rows seeded at shallower depth accessing stratified K. Deficiency symptoms appearing in rows seeded deeper.

K Uptake and Removal by Crop Type

K requirements vary substantially based on crop type, (Table 3). Although some of the crop types listed below have high requirements for K such as peas and fava beans. Barley seems to be the most sensitive to K deficient soils and the crop type we see deficiency symptoms in the most often. 

Table 3. K20 taken up by various crops. Source: Saskatchewan Ministry of Agriculture.

Opportunities for Management with SWAT MAPS.

Understanding K allocation within your fields using SWAT MAPS allows for more precise management. SWAT MAPS allows you to take your existing fertilizer budget and allocate nutrients like K to areas that need it the most. That could be areas of the field that are testing deficient or areas of the field where you are most likely to see a response based on the soil properties mentioned above. ROI on applied potassium can be improved using SWAT MAPS, especially if doing applications in large quantities to build soil test levels. 


The need for potassium. (n.d.). Potassium fertilization in crop production

Ethan Rheaume
Precision Agronomist

It’s only going up from here for FM Agronomy

Beth Martel, owner of FM Agronomy, says she anticipates seeing 90% of growers using some sort of precision within the next 15 years. For those who aren’t there yet, FM Agronomy’s goal is to help them get there as seamless as possible.

“SWAT MAPS is my go-to. It’s opening up that opportunity for precision agriculture,” she says. “Even with years of agronomy behind me, I focus on the SWAT MAPS side of things and continue to get stronger and more precise with it.”

Named after their 103-year-old farm Ferme Martel Ltd., FM Agronomy officially started up as a family-run business in 2018. Originally from Wales, U.K., Martel moved to Manitoba in 2001 and grew up on a mixed cattle farm, stemming her passion for agriculture. As FM Agronomy continues to strive to support customers in reaching their soil and yield potential, the company anticipates major growth while continuing to service the Southcentral Manitoba area.

“We’re very interested in conversations with growers who have a ‘go-get-it’ attitude, but also with those who want to carefully walk through the process step by step,” she says. “We’re dedicated to not spending your money for the sake of it, but rather putting your money in the right spot.”

Being more efficient is a top priority for FM Agronomy, but bringing customers face-to-face with new methods isn’t always easy.

“Some aren’t so sure, so we go out with them to the field with a tablet and check things out right upfront,” she says. “Some are hesitant on variable rate, but then it makes sense when they do it. For example, we’re not putting fertilizer in those areas where it’s going to have runoff, we’re putting fertilizer where it matters. We really focus on what’s not going to waste money.”

The SWAT MAPS Team is proud to work alongside dedicated teams like the one at FM Agronomy. Stay tuned with what’s happening in their area of Southcentral Manitoba by following them on social media or visiting their website:

Twitter: @Bmartelag

Farmers: visit to find a SWAT MAPS Service Provider near you. 

Service providers: Contact us for partnership opportunities.

Progro Agriculture on SWAT MAPS: Answering the ‘Why,’ Being More Than a Map, and Setting the Gold Standard for VR

As a ‘one man show,’ Maury Micklich started Progro Agriculture in 2022, cautiously optimistic as to whether or not he could grow the business. Based out of Holden, AB, Progro planned to be tailored to agronomic consulting services at first with SWAT MAPS as the added sweetener, but quickly found his SWAT MAPS service to be so popular it became his main offering. 

“SWAT MAPS has helped drive my business,” said Micklich in a recent interview. “Thankfully there is now zero doubt about the success of the business and the future of it. Just having SWAT MAPS as a part of my business has brought new clientele out of the woodwork. Word of mouth is spreading that I’m doing SWAT MAPS and customers have come my way. It has really taken over my business, in the best way.” 

Answering the Why 

Although Micklich’s customers always recognized that there were certain responses happening in their fields, there was always the question of why.

“There have been the typical soil/water issues and some not so typical surprises,” Micklich asserts. “Everyone knows there’s areas that don’t produce well but can’t always identify the why. With SWAT MAPS, I’ve been helping identify these areas of the field and the drivers of the response that they’re seeing. Together we’re connecting the dots of what and why things are happening the way they are.”

Being a farmer as well as a SWAT MAPS Service Provider, Micklich has found this has really helped him be relatable. With a mission of chasing value for his customers, being able to implement SWAT MAPS technology on his farm and then bring the results to his customers has helped them succeed.

“The biggest thing is being able to relate. I’m comfortable experimenting where maybe some people aren’t,” said Micklich. “I can then show the results I’m seeing and maybe they’ll see the value in it or at least open their mind to it. I’m very involved, I want to be fair and I want everyone to succeed. If I can help other farmers be successful, that’s my end goal.” 

More Than a Map

Progro Agriculture is situated in a fertile, agronomically competitive area in Northcentral Alberta, servicing a wide area of customers from Fort Saskatchewan to St. Paul to Camrose and Killam. Having previously worked with products similar to SWAT MAPS, Micklich has had experience with other maps and openly expresses his affinity for SWAT MAPS.

“Dealing with other products before, SWAT MAPS is easily the most precise,” said Micklich. “You won’t get a map that more accurately defines the field. It really gives a holistic picture of the variation in a field. Great value and best damn precision!” 

Although he sees firsthand the many advantages of SWAT MAPS, Micklich also understands the hesitancy of farmers to utilize variable rate (VR).

“One of the biggest barriers I’ve found that my customers have towards VR is the ROI. Some are hesitant because they think it won’t have any benefit. My customers have told me that SWAT MAPS value proposition greatly exceeded their expectations. I’ll drive the value nail as deep as I can – you’re getting value because you’re not just getting the best map. You’re getting the whole SWAT ECOSYSTEM.” 

Setting the Gold Standard for VR

Over his last year of business, Micklick has seen VR evolve from being a second thought to a first decision. “The reputation of VR is changing,” Micklich states. “It’s becoming a staple on the farm rather than the option.” 

As SWAT MAPS becomes more and more popular, Micklich notices his competitors trying to replicate his services.

“Everyone is trying to mimic our recipe,” he observes. “Competitors are trying to model the value proposition and are suddenly adding more zones to their maps. If everyone is trying to copy it, that’s a pretty good indicator that we’re doing something right. It is setting the standard for VR services not just in my area but around the world.”

The SWAT MAPS Team is proud to work alongside passionate, independent agronomy service providers like Maury Micklich. Learn more about Progro Agriculture and what’s happening in their corner by following them on social media or visiting their website:

Twitter: @ProgroAg

Farmers: visit our Partner Locator to find a SWAT MAPS Service Provider near you. 

Service providers: Contact us for partnership opportunities.

SWAT Partner Announcement: Prairie Shore Agronomy Inc.

East Central Alberta farmers: are you wanting to put more thought into exactly where your inputs are going, and how effective they’ll be? New SWAT MAPS Service Provider Prairie Shore Agronomy Inc. is ready to chat all about it.

It didn’t take long for Jade and Colton Almberg, owners and operators of Prairie Shore Agronomy Inc., to come face-to-face with the reality of input prices reaching new heights in recent years, combined with the inherent variability of soil conditions in his region. After taking this into consideration, a major next step was to refine their approach to allocating input resources.

“The paramount goal is to direct input dollars towards soil that promises not only enhanced profitability but also adheres to sound agronomic principles, ensuring sustainable agricultural practices for the future,” says Colton.

Founded in 2022, the company out of Czar, Alberta, consists of three employees servicing the East Central Alberta area as well as Southwest Saskatchewan. The team takes pride in embracing a symbiotic relationship with their growers, walking alongside them through every stage of their journey.

“Our genuine care for customers and their operations extends to a level where their successes become synonymous with our own triumphs,” says Jade. “Our vigilance in monitoring crops for any potential issues drives us to provide innovative and effective solutions that are not only economically advantageous but also firmly rooted in agronomic and environmental integrity.”

As a SWAT MAPS Service Provider, Prairie Shore Agronomy Inc. will focus their efforts on analyzing fertilizer and herbicide usage rates, seeding population, and increasing the ease of harvesting through maturity optimization – all through the use of SWAT MAPS technology.

Join us in welcoming Prairie Shore Agronomy Inc. to our elite network of SWAT MAPS service providers by following them on Twitter:

Colton Almberg - AlmbergColton
Jade Almberg - @MrichardsJ

Why Variable Rate, Why Now?

Variable rate technology is becoming more commonplace in the ag community, yet the adoption rate is still relatively slow. Some surveys suggest there is less than 10% adoption of variable rate by Canadian farmers. However, it’s possible that the adoption rate is about to grow exponentially in the coming years. Farmers are realizing that an effective variable rate program like SWAT MAPS is very important, especially now. Here are five reasons why. 

Optimize the Use of Inputs

These days, farm input prices are very high, so it is becoming even more critical to not waste them. Variable rate technology enables precise management of resources such as fertilizers, pesticides, and even irrigation water. By applying these inputs in varying amounts based on soil, water, and topography characteristics, farmers can optimize their resources (see Figure 1). This leads to increased efficiency, reduced waste, and cost savings, making it an essential tool for sustainable and environmentally friendly practices.

Figure 1. SWAT MAPS recommendation report showing different seed and fertilizer rates for different zones.

Evenness of Crop Maturity

Protecting the growing crop has never been more important. Variable rate seed and fertilizer  will promote even crop staging and maturity (Figure 2). Achieving a proper plant stand will minimize excess tillers or branching that delays maturity and causes uneven crop staging throughout the season. This can significantly improve control of diseases such as fusarium head blight and hasten maturity in low areas that are normally too delayed to harvest when the rest of the field is ready. This has very high value for all farmers but especially for seed growers who need seed viability or can't use glyphosate as a preharvest aid. Not to mention the value of getting the crop off before that storm hits!

Figure 2. Standing wheat with even maturity. Photo: CropPro Consulting

Enhanced Crop Productivity 

Optimizing yield wherever possible is crucial. When using a fixed rate application of inputs, farmers are forced to use field average rates. For example, they can't optimize yields in those areas that would benefit from more fertilizer because other areas in that same field may be prone to lodging and would therefore see a negative impact from more fertilizer.

Alternatively, farmers using variable rate technology can increase fertilizer rates in areas that would benefit from it and decrease it (or even shut it off completely) in areas where more fertilizer would be detrimental. By providing the right amount of nutrients, and other inputs, to each part of the field, this technology helps optimize crop growth and yield, which can therefore result in improved productivity and profitability for farmers.

Figure 3. Standability of wheat when using VR vs fixed rate inputs. Photo: Amber Knaggs

Site-Specific Management 

Especially these days, farmers must reduce costs whenever they can. Fields often exhibit spatial variability caused by differences in soil properties, topography, and other factors. SWAT MAPS help farmers address these variations by creating management zones and treating each zone differently. Perhaps there are only certain zones within a field that would benefit from application of a micronutrient. Since that micronutrient may not provide an economically significant benefit to the rest of the field, variable rate prescriptions can be made to apply the product only in the areas where it is required. This approach can dramatically reduce costs and increase ROI since unnecessary application of product in other areas of the field can be eliminated.

Figure 4. Severe P deficiency in wheat typically observed on high pH, eroded knolls, delineated as SWAT zone 1. Photo: Amber Knaggs

Environmental Sustainability

Proper use of variable rate technology plays a vital role in sustainable agriculture. By precisely targeting inputs, it reduces the potential for over-application of fertilizers and chemicals, minimizing the risk of environmental pollution and nutrient runoff into water bodies. Additionally, variable rate can even promote responsible water management by optimizing irrigation practices, reducing water usage, and minimizing soil erosion.

In fact, here in Canada, substantial government funding is now in place through the On Farm Climate Action Fund (OFCAF) to help farmers farm even more sustainably. There are various organizations that farmers can apply for funding through. Below are a few of them:

There are many other reasons why variable rate technology is important, but essentially, when a great variable rate program is combined with great agronomy, it offers better resource efficiency, increased productivity, better crop management, and environmental sustainability. Furthermore, right now our government is willing to subsidize farmers who want to make variable rate application a part of their operation. There is no better time than now to get started.

If you would like to further discuss how variable rate might benefit your farm specifically, please connect with us at Or you can find more information elsewhere on our website.

Chris Hawkins
Director of Sales – Farmer Services

Make it Count: How to Harvest Field Trials

Trials are an important part of our learning about how different treatments benefit each SWAT ZONE.  Whether it is a replicated trial, a casual strip trial or a field split in half, collecting the data at harvest time is key for future decision making.  

About Our Process

The SWAT MAP Yield Potential team approaches trial data differently than processing yield on a field scale.  First, because we are dealing with smaller areas, we use a much higher resolution map.  Then, we manually clean the raw point data to ensure the maximum amount of quality data is preserved.  Data points too close to trial edges are removed to reduce the effect of any overlap between treatments.  Headlands and passes around sloughs or obstacles are also removed.

Figure 1. Cleaned yield points within the trial boundaries.

Best Practices for Harvest

The most crucial part of harvesting trials is direction.  Harvesting along the same direction as the trial strips will preserve as much of the data as possible and make those results most accurate.  Because we clip the data close to trial boundaries, harvesting at 90 or 45 degree angles will reduce the usable data by 50-70%.  

Direction is so important that our GIS team will design trial strips to match what farmers intend to do.  We implement square blocks instead of strips for farms that harvest on 45 degree angles.

Figure 2. Trial design for a diagonal harvest direction

When possible, use the same combine to harvest the trials and a minimum of 2 surrounding passes.  This way we can rule out machine discrepancies in the data and have enough data around the trial to use as a control.  For large trials where a field is split in half, try to run your combines side by side so an equal area is covered by each machine in each treatment area.  The same principles also apply to swathing.


Trials often have a wide range of yields between treatments and different SWAT ZONES.  To accurately capture this, it is important to calibrate your combines at different flow rates to ensure the yield monitor is reading correctly regardless of the crop conditions.  

When using a weigh wagon, it is important to keep accurate, easy to understand records of the weights and what is being weighed. Also ensure the units of measurement are clear. Measuring bulk density (bushel weights) is also helpful. 


The cleaned data points are sorted by SWAT ZONE and analyzed for statistical significance.  This is done by using each data point in the trial and zone area, not just by average yield.  This method takes into consideration the variability that may exist in each trial.  

Our findings are presented to the farm in graph and chart format.  The agronomist will include an interpretation of results along with recommendations for future use.

Considering a Field Trial?

We are excited about learning how products and treatments interact with each SWAT ZONE.  Talk to your SWAT MAPS service provider about requirements and funding opportunities.  

Danielle Epp
Yield Potential Manager

How to Prevent Crop Lodging with VR Seed and Spray Applications

Crop lodging is a significant problem that leads to decreased yields, deterioration in seed quality, and decreased harvestability ease. Crop establishment that reaches target plants/sq ft and proper nitrogen  management contribute to decreased lodging risk later in the growing season.

Figure 1. SWAT MAPS Management Zones Based on Topography

Early in the growing season it is common to see abundant moisture. Under wet soil conditions crops grow poorly developed shallow root systems. Areas of a field that are typically water holding with excess moisture are SWAT Zones 7-10. These are the areas that you will notice lodging later in the season because the crop has a poorly developed root system with excessive above ground growth. An established crop stand will use soil water more efficiently. SWAT MAPS can aid in establishing a good crop stand by using variable rate technology to apply seeding rates. When variable rate seed is practiced, seed rates are increased in higher mortality zones, which commonly includes Zones 7-10. Increasing seeding rates in these high mortality zones improves the crop plant stand. Variable rate seed applications aid to target plants/sq ft evenly throughout zones in a field. Reaching plant stand targets reduces excessive tillering that shallow root systems can not support later in the growing season. 

Figure 2. Variable Rate Barley Seed

SWAT MAPS have proven that there is significant organic matter content variations throughout zones. The more organic matter in a soil the more nitrogen mineralization that will occur throughout the year. During the mapping and soil sampling process, SWAT MAPS identifies the areas that are lower and higher in organic matter. We know that  excessive plant growth follows excessive nitrogen application which leads to lodging. We can variable rate nitrogen applications based on the knowledge of residual nitrogen levels left in the soil from the year prior while taking into consideration the amount that the soil will mineralize throughout differrent zones. Utilizing variable rate nitrogen applications will prevent lodging by ensuring the crop does not have excessive nitrogen in the soil and this practice will also aid in even crop  maturity. 

SWAT MAPS has the capability to also create variable rate spray applications. In the case of preventing lodging, we can variable rate apply plant growth  regulators (PGRs). PGRs promote stronger stems to mitigate lodging. Fields that are a fit would include those with poor burned out crop zones due to drought or poor drowned out crop zones due to excessive moisture all season long.

Figure 3. Organic Matter Variation Throughout Zones

SWAT MAPS can reduce lodging risk by providing the technology to variable rate seed, fertilizer and spray applications. These applications will enhance plant establishment to reach target plant populations throughout zones in a field. The applications will also provide nitrogen management throughout zones. SWAT MAPS will not only reduce lodging risks but will also even maturity for harvest profit and easeability. 

Rachelle Murrison
Precision Agronomist

Max Ag Consulting: Finding value in VR, doing it right, and building a successful agronomy business

When Mike Palmier started Max Ag Consulting as an agronomy consulting company in 2019, he never expected that SWAT MAPS would become the core of his business and his scouting work would be complimentary.

“I started an agronomy consulting company and now we’re more of a services company with an agronomic focus,” said Palmier in a recent interview. “None of this was in my five-year plan. Our partnership with SWAT MAPS has helped us grow bigger than we ever expected. SWAT MAPS is central to our business and our customers.” 

Finding value in VR

As a SWAT MAPS Service Provider, Max Ag Consulting works with farmers within 150kms of Plenty, SK. Four years into utilizing the SWAT MAPS technology, Palmier says he has seen many shifted mindsets in farmers. Farms in year three or four of using the technology are starting to see big differences after initially being hesitant to test it out. 

“Some of our customers right off the bat said they weren’t interested in VR and didn’t believe in it. We continued with their scouting and once they started learning about the differences in areas of their field, the lightbulb came on,” states Palmier. “What we can do with the maps starts to make sense to them. Farms aren’t doing what’s cool. They want to see the results.”

Palmier’s customer acre retention rate is now above 98% and customer referrals are generating significant business for him.

The mission of Max Ag Consulting is to help their clients make better decisions in order to maximize their field potential. “SWAT MAPS isn’t just a map telling us where the crop is better or worse. We analyze the data and learn from historic trends, nutrient responsiveness, and more,” said Palmier. “For example, we found we can get as big of a return on investment with adjusting seeding rates as we can with varying fertilizer rates. We’re helping identify issues and creating strategies to improve crop production with VR.” 

Not pressing the easy button

Now consisting of six full time employees, Max Ag Consulting strives to provide honest and proven agronomic advice to their customers. “We aren’t afraid to do the hard work,” said Palmier. “It would be easy to send a spray application without ever checking it, but is that the right thing to do? We don’t press the easy button with precision ag or VR.” 

“SWAT MAPS has changed our whole thinking of what’s going on in the field. We analyze a lot of data with SWAT and we’re learning a lot about trends in historic data, nutrient responsiveness and more,” said Palmier. “We’re continually ground truthing our assumptions and improving our understanding year after year, while also learning how the crop is responding in different environmental conditions.” 

The challenge of precision ag

Understanding where precision agriculture has a practical application on farms is a top consideration for their team of agronomists. “We continue to work with our customers on taking new technologies and ensuring they fit on the farm. The challenge of precision ag is the industry tries to build everything on a computer and they don’t have people in the field to validate it. We’re constantly asking how we can make the machines and people work together seamlessly. We’re in the middle helping our customers with the adoption of technology. We make sure it’s the right fit for them and will bring the results they are looking for.”

The SWAT MAPS Team is proud to work alongside dedicated teams like the one at Max Ag Consulting. Stay tuned with what’s happening in their area of West-Central Saskatchewan by following them on social media or visiting their website:

Twitter: @MaxAgConsulting

Farmers: visit to find a SWAT MAPS Service Provider near you. 

Service providers: Contact us for partnership opportunities.

Understanding Site-Specific Field Variability and Modifying SWAT MAPS

One of the best times to assess fertility and moisture-based variability within fields is as the crop is coming into maturity. This is when moisture stress and nutrient deficiencies have the potential to show up. It is when lodging and delayed maturity issues in areas of the field are more pronounced. A late-season crop assessment is beneficial for identifying problem areas and creating a management plan to address these concerns. Managing your crop using SWAT MAPS can help even out crop maturity. If you are already a SWAT MAPS customer, it is also a great time to validate the chosen SWAT MAP.

After a field has been mapped, an agronomist ground-truths the field and selects the map option that best represents what they are seeing at the time of soil sampling. The highest and driest areas of the field should be grouped together as a zone 1. The wettest, most saline (if you have salinity) areas of the field should be a zone 10. There are times, however, that the map can be modified as we learn additional information about the field. This is one benefit to having agronomists and growers actively assessing crops and fields during the growing season, and seeing how everything aligns with the map. 

General field variability

Many factors can cause variability in a field. We are interested in capturing soil, water and topography attributes with our maps. These are stable properties and no matter how flat the field, water always goes somewhere. The texture differences across the field will always be variable. 

Field variability in dry years

A particularly dry year can accentuate variability in your field. For example, a subsoil gravel seam may not be noticeable in a wet year but in a dry year, crop growing on that seam burns up early in the season. Light or moderate salinity may not be noticeable if a field has been getting ample moisture, but really shows up when rain is limiting. 

Checking crops during pre-harvest staging and making note of these variability factors can help us better manage these areas in the future. A SWAT MAPS agronomist or service provider will ground-truth the SWAT MAP and see if the variability is matching up with the map or the electrical conductivity (EC) layer. 

Example modifications to a SWAT MAP

At Croptimistic, we don’t claim to be perfect but are always striving to do better. SWAT MAPS are a solid tool for land management and can always be improved upon. We often make improvements to pre-existing maps. Our agronomists visit the fields during the growing season to do general agronomic assessments. Every year has the potential to be different, but the main goal of these assessments is to evaluate if the strategies we employed in the spring are working. Is the crop more even? Is there opportunity for additional modifications and changes to upcoming fertilizer strategies? Are certain areas of the crop burning up, and is there opportunity to modify our fertilizer strategy to reduce risk in these areas? Are these areas lacking fertility? There are a multitude of potential questions to be answered. 

Occasionally, we come across a situation where the agronomist may feel it is necessary to modify the SWAT MAP we chose during the soil sampling stage in the first year. A common modification to a map involves creating a “mod area” where a known past management practice changed only a small area of the map. For example, bush/trees, corrals, or old yards were removed, or old septic fields are no longer in use. These areas won’t necessarily be picked up in the final map or in “normal years,” but past management practices resulted in these areas mineralizing more than the rest of the field. We can add a mod area so we can better manage the specific area with our fertilizer recommendations. 

Another modification can include changing the SWAT zones to better align with persistent environmental factors, which may include underlying subsoil features that change only in particular zones.   

Case study: modifying a SWAT MAP due to isolated soil texture differences

Figure 1. Original SWAT MAP chosen in Fall 2020. Zone 1 was the highest area of the field and zone 10 was the wettest area of the field. 

During a pre-harvest VR assessment in 2021, it was noted that there was an area of a field maturing significantly earlier than the rest. This area in question was not located in the typical driest zone 1 highest topography area of the field, but was more closely aligned with the lower EC area. This scenario provided us with the opportunity to modify the SWAT MAP to delineate and isolate the coarse-textured soil in this field, which was verified through review of past NDVI imagery.

Figure 2. Picture of the area in question, taken during the pre-harvest VR assessment during a dry growing season, which alerted to us to review a modification to our SWAT MAP. (Photo credit: Jill Sparrow)
Figure 3. The modified SWAT MAP which isolates zone 1 to the area with subsoil sand. 

The top of the hill on the most northern part of the picture is now a zone 2. The new zone 2 area is up on a hill and is still classified as drier but has greater moisture-holding capacity than the new zone 1 area.  These areas can be now managed differently because of the edited SWAT MAP. 

Managing field variability using SWAT MAPS

Soil testing by zone is an important tool to manage fertilizer requirements after a drought year. If  crop yield was poor on the hilltops and sidehills, it is likely there will be higher residual nitrogen levels in those areas. In contrast, normally high producing toe-slopes and depression areas not impacted by salinity may have very low residual nitrogen levels because high crop yields could have removed a lot of nutrients. 

SWAT MAPS are the foundation of all variable-rate fertilizer and seed applications and enable farmers to better understand field variability in order to optimize crop inputs and profitability. While imagery-based maps tell you what variability exists in your crop and where, SWAT MAPS delineates soil, water, and topography factors for a comprehensive understanding of why the variability exists and how to better manage it. 

Contact us today to book your acres for better understanding and management of your field variability. 

Differences in OM and soil texture across a field in Northern Saskatchewan
Crop maturing sooner on a zone 1 sandy area.

Kerrie de Gooijer, PAg, CCA
Senior Precision Agronomist

Making Sense of Soil Moisture Graphs

The SWAT MAPS weather station team installs and maintains many weather stations in Western Canada with soil moisture probes for our customers. This technology gives us a window into what is going on beneath the surface and how the roots are interacting with soil and using water. Soil moisture data has gives us further insight into how the crop is performing and can be beneficial for in-season top-dressing applications, for understanding yield analytics post-season, and more.

The team works with different kinds of moisture probes that have between 5 and 12 depth sensors that report hourly readings of soil moisture conditions. Each moisture probe is installed in the field after seeding, positioned between the crop rows, ideally in a SWAT zone that represents the average for the field. This allows us to see how soil texture, heat, root behavior, and rainfall events affect the soil moisture profile.

In the first example (above) we have a crop that got a good start to the season and has strong root activity down to 70 cm. The initial soil conditions here were good and the crop was able to develop a good root system that could take advantage of the moisture at depth during the mid-June heat.  

A rainfall event recharged the soil moisture at 10 cm and just marginally at 20 cm.  After this time, root activity stops below 50 cm. Why extend the energy to the deep roots when there are plenty of easily accessible moisture close to the surface? As that water is used up without additional rainfall the roots at depth will begin to draw moisture again. This also has consequences for nutrient uptake depending on where those nutrients are in the profile. As the topsoil nears wilting point, highly stratified nutrients like phosphate, zinc, potassium, and potentially others may become deficient as the plant continues to grow well on subsoil reserve moisture.

The next example is unique in that it comes from a research site where we have placed the moisture probe in SWAT Zone 10, where we know there is excess moisture.

During installation, it was noticed that the water table was high at this location. You can see in the straight lines of the graph at 70 and 100 cm that nothing is draining here. The water table was at 70 cm depth when the moisture probe was installed. The next rainfall event moved that up to 50 cm and very briefly to 30 cm before draining back off.  

A second larger rainfall moved that water table back up to 30 cm for 2 days before draining off again. The 50 and 70 cm sensors start to drain off shortly after as the crop starts using more water. Then in mid-June we finally see the water table drop below 100 cm. 

So what does this data mean, and why is it so invaluable to keeping in your back pocket?

Each time the water table comes near the surface, crop stress and denitrification is likely to occur, helping us to make in-season management decisions, or understand why final yield is not as good as expected. It would also help explain developing salinity problems that need to be addressed with subsurface drainage.

This example is what a full soil moisture profile looks like. The first large rain event of the season brought the moisture levels up to field capacity. You can see the graph lines for each depth sensor spike up and then down again rapidly as the water drains. Over the next few days smaller rains gradually increase the water level at depth so when the next large rain event occurs it can’t hold anymore. After this point the graph returns to the saturation point after each rain. As root activity develops deeper those levels will gradually drop off.

This data shows us that mobile nutrients like nitrogen, sulfur, and chloride are potentially leaching below the current root zone. If it were to show movement deeper than the crop’s typical root depth, topdressing may be required to match water-driven yield potential and account for leaching losses.

This last example is what happens when different soil textures are present at depth after a multi-day rain event. At the surface, this soil is a silty clay loam which trends toward heavier clay at depth, except for a layer of sandy loam at 110 cm.  It is this sandy layer that is shown by the lowest line on the graph.  

After four days of rain the water has moved through the soil profile and slows down as it hits the lowest layer of clay at 120 cm (shown on the top line of the graph). Water is building up at this point and the sensors at 110 and 100 cm spike up as the water collects. This is particularly dramatic with the sandy loam soil which typically does not hold that much water. As the water drains over the next few days you can see it returns to normal levels.

It's the type of information that you didn’t think you needed, until you do.

Soil moisture probes can provide useful information about how water interacts with the crop and soil textures in the field. Observing data from research sites shows how different SWAT Zones will respond to different moisture conditions. Recognizing a need for drainage solutions, understanding crop stress and yield potential, or managing nutrients in season with SWAT MAPS are all potential benefits of good soil moisture data.

The SWAT MAPS team is here to guide decision making to help you make the best use of this technology. Reach out to get started or to discuss ways on maximizing the work your weather station does for you.

Danielle Epp
Yield Potential Manager