How to Implement the SWAT MAPS Yield Potential Program to Maximize Your Potential and Cut Costs

Hana Ruf
Regional Manager, East Central SK
hana@swatmaps.com

SWAT MAPS variable rate technology is the first step in maximizing efficiency and productivity through fertilizer, seed, and soil amendments. Once a farm has been fully mapped and the client and their agronomist feel they have a solid fertility plan, they might be wondering what else they can do to improve their practices. The Yield Potential Program (YPP) is for SWAT MAPS clients who want to take their VR potential to the next level. Included in the YPP are unlimited in-season prescriptions, yield analysis, and SWAT CAM.

Unlimited In-Season Prescriptions

Unlimited in-season prescriptions can be made using the SWAT MAP itself, SWAT CAM maps, or NDVI satellite imagery. There are many uses for in-season prescriptions such as on/off or VR fungicides, herbicides, insecticides, plant growth regulators, top dressing, and desiccation/pre-harvest.

Figure 1 is an example of an on/off fungicide prescription that was applied by a ground sprayer using an NDVI map. In this case, areas of the field had minimal crop growth due to dry conditions and sandy soil, and in other areas due to high salinity. The fungicide was turned off in these areas (zones 8-10 on the NDVI map), saving the client $538 on this 150 acre field. If these in-season prescriptions were used across 5,000 acres and fungicide was turned off 20% of the time, in places where it is not needed, the savings alone would pay for the cost of the YPP subscription ($2/ac).

Figure 1. In-season prescription for on/off fungicide for a 150 acre canola field. Prescription is on the left, and resulting application map is on the right.

SWAT CAM

SWAT CAM maps are most often used for top-dressing and herbicide applications. One example of an easy way to save money using SWAT CAM is to target kochia with products such as Authority® (sulfentrazone) or Edge® (ethalfluralin). Figure 2 demonstrates a prescription that was used for an on/off Edge application based on both the SWAT MAP and the kochia map. The Edge is turned on in zones 7-10 on the SWAT MAP, as well as in any places where the SWAT CAM identified kochia plants to ensure good coverage. The Edge was turned off for 74.7% of this 160 acre field, saving $3935.

The SWAT CAM is also very useful for helping identify issues in a field such as nutrient deficiencies or drill issues. It is a useful tool for directing scouting efforts and checking on “problem” areas of a field. A quick reference to a SWAT CAM photo in a saline zone 10 can indicate how well the crop is growing there, and if you should adjust your seed or fertilizer rates there in future. The SWAT CAM provides clients and agronomists with unbiased, high resolution plant stand counts for canola, corn, soybeans, and potatoes. Future adjustments to seed rates can be made based on these plant stand counts.

Yield Data

As agronomists, we consider many factors when deciding what fertilizer rates to apply in each zone on a field. We use the SWAT MAP, soil tests, and general knowledge about the field and region to ensure we are not over or under applying seed or fertilizer. As a result, we see many benefits such as increased fertilizer efficiency, reduced lodging, more evenly maturing fields, and increased profitability. However, we are missing an important piece of the puzzle by not knowing exactly how our decisions within a field are affecting yield and ROI. At the end of the season, we don’t get a “report card” to know where the highs and lows were in a field or on a farm. In the YPP, client yield data is cleaned, analyzed, and used to fine tune our decisions going forward.

YPP provides useful data for each field such as actual yield by zone, yield vs. farm average by zone, multi-year yield % of average by zone, stability maps, and profitability maps and graphs. We have been successfully using these tools to identify where we are both overestimating and underestimating yield potential, whether on a zone scale or entire field scale.

Figure 3 shows a field where we were continuously underestimating the yield potential of the entire field, especially in zones 1, 2, and 10. This was a common trend on this entire farm, so in 2024 we adjusted the yield goals (Table 1.) and fertilizer rates to try and achieve even greater yield in these areas. After a few years of doing this, we can gain confidence in just how much we can push these yields and know what our potential really is. This will allow us to maximize ROI by aiming for our maximum yield potential without overapplying fertilizer to achieve it.

Figure 3. Yield % of Average by zone; 2022 canola actual yields versus target yields by zone.

Table 1. Canola yield goal, actual yield, and adjusted yield goal for example field.

Zone	Acres	Yield goal 2022	Actual Yield 2022	Yield Goal 2024
1	6.9	30	53	55
2	41.8	35	60	60
3	85.3	40	62	60
4	95.3	45	63	65
5	106.7	50	63	65
6	122.3	50	62	65
7	156.9	50	61	60
8	99.4	50	58	60
9	26.6	45	52	55
10	8.6	35	51	50

We might also identify fields or zones in which we are overestimating the yield potential. The field in Figure 4 is a poor yielding field historically and has a very sandy zone 1 and 2. When we looked at the actual vs. target yield for each year, we were always well below our target in these zones and on the field average. We knew the yield was poor in zones 1 and 2 and did adjust the yield goals and fertility for that, but we were still overestimating the yield potential even in years with adequate rainfall. Looking at the yield vs. farm average by zone and seeing how poor this field performs compared to the rest of the farm, we decided since this is a higher risk field we might be better off scaling back the fertilizer and yield goals and allocating that budget to better performing areas on the farm. This will help mitigate the risk and manage inputs properly.

Figure 4. A poor performing field with very sandy zones 1 and 2 that consistently yield lower than the farm average.

Clients can provide their input costs and selling prices to attain profitability maps and analysis through the YPP. This can help us improve margins and increase profitability both in good producing zones and troublesome zones. Zones 6 and 7 in the field in Figure 5 are at 32% of the profit margin (profit margin = profit/income). The yield data analysis provides this information, and then the client and agronomist can determine the “why.” We might be able to use SWAT CAM images to provide us with more information. We can then decide if there is a way to increase these margins. Is the solution in the seed or fertilizer rates? Do we need better drainage? If the profit margin in zones 6 and 7 can be increased by 2%, that would be an additional $30/ac. At 160 acres, that is $4800.

Figure 5. Profit Margin Analysis by Zone for a 160 acre field.

Summary

There are many use cases for the Yield Potential Program. Unlimited in-season prescriptions provide clients with an efficient and cost reducing alternative for applying pesticides. SWAT CAM provides options for directing scouting efforts, diagnosing and assessing issues in a field, and unbiased plant stand counts. The yield analysis component has many benefits which all help to fine-tune seed and fertilizer management and improve profitability.

For more information or to sign up for the Yield Potential Program, call 1-800-421-4099 today!

High resolution plant stand assessments with SWAT CAM

Brandon Smith
Regional Manager, Central SK
brandon@swatmaps.com

Having a consistent and even plant stand across a field is beneficial in achieving even maturity and maximizing yield. Consistent maturity is critical for fungicide staging (especially for fusarium head blight in wheat) as well as harvest timing. At Croptimistic we use SWAT MAPS to not only vary rates of fertilizer but also to vary seeding rates. This allows us to have a nice, even plant stand. Conditions in the defined SWAT zones will affect seedling mortalities, therefore we can increase seeding rates in those zones to even out plant stands (Figure 1). Typically, zones 1-2 and zones 9-10 will have the highest mortality depending on the field’s soil properties and moisture conditions. These zones will have the highest seeding rates. Zones 1-2 are drier areas of the field that are water-shedding and can often have lighter textured soil, tend to have shallower seeding, and can dry out when it is hot and windy, which increases mortality. Zones 8-10 can often be “mudded in” as these areas are wet when seeding, can have permanent soil issues such as salinity, peat, or sodicity, and these factors again, will increase seed mortality. In the end, we typically prescribe the same amount of seed as we would for a flat rate, but redistribute it to optimize the final plant stand.

Figure 1: Example of VR canola, wheat, and pea seed prescriptions from left to right. Increasing the seeding rates in Zones 1-2 and 8-10, as these zones have higher mortality.

It is important that we assess our VR seeding rate strategies to ensure that we are hitting our plant stand targets across SWAT zones. Before SWAT CAM, the process for doing this was by manual plant stand counts, which involved counting a few different areas in each zone to come up with an average plant stand count across zones and across the field. This method was very labor intensive and low resolution, since we are counting limited locations in a few fields across a farm to assess our VR seed strategy. As we know, different fields will have different seeding conditions, soil types, and therefore different mortalities. Manual plant stand counts are not able to capture all variability within every SWAT zone across a farm.

Figure 2: SWAT CAM system mounted to sprayer boom

SWAT CAM is a camera system that is mounted to a sprayer that is automatically capturing 1000s of images on every field, running those images through a machine learning algorithm, and getting plant stand counts for several crops. As of today, SWAT CAM can count individual plants in canola, corn, soybean, dry bean, faba bean, and potato. In 2024 we will be beta testing plant stand counts for cereals and lentils.

Figure 3: Example of SWAT CAM image with canola plant stand count model.

SWAT CAM allows us to accurately assess our VR seed strategies on the crops that we have plant count models for. As shown in Figure 3, we can count individual canola plants and calculate the average plants per square foot in that image; in this example the average was 5.5 plants per square foot. The seeding rate in this zone was 4.3 lbs/ac and calculated mortality was 44%, which is slightly better than the industry standard for canola seed.

Figure 4: Canola plant stand count by zone with calculated mortalities.

With 1000s of counts across the field analyzed by SWAT zone we can then get an average of the whole field and an average plant stand for each SWAT zone. This data can help us to adjust our VR strategies. For example, if SWAT zone 1 has a higher plant stand than we were expecting, and zone 1 received the highest seeding rate, then in the future we can consider decreasing the seeding rate resulting in reduced seed costs. Another example may be that certain fields on the farm tend to have lower mortality across the whole field and the plant stand is always higher on those fields. This is another opportunity to decrease the seeding rate. Alternatively, fields with higher-than-expected mortality should be investigated further. Do seeding rates need to increase or are there other factors causing the high mortality that need to be altered, such as residue management, fertilizer placement and seed-placed rates?

SWAT CAM data allows us to calculate mortalities across SWAT zones by comparing the seed rates applied to the actual plant counts calculated by SWAT CAM. Automation of this process allows us to capture optimized plant stand counts across full farms at a low cost. SWAT CAM increases our confidence in our plant counts such that we can make better decisions and adjustments to variable rate seed strategies.

Using SWAT MAPS to optimize fertility recommendations, reduce crop Inputs, and save $$$

Sean Barath
Precision Agronomist
sean.barath@swatmaps.com

Introduction
Every fertilizer recommendation should start with soil test data. Without soil test data you would basically be making blind recommendations, based on yield goals and crop uptake/removal tables. This is not an ideal method of nutrient planning as you could either over or under apply certain nutrients.

Soil Testing
Composite soil testing (Table 1) can be a good starting point for making fertilizer recommendations for flat rate applications; however, it only captures soil nutrient levels in the mid-slope areas of fields, leaving out important information on soil nutrient levels in depressions or hilltops. Implementing zone-based soil sampling (Table 2) along with the use of SWAT MAPS variable rate seed and fertilizer can help producers get their best ROI on inputs and save money.

Table 1. Example of composite soil sampling test results.

Table 2. Example of zone-based soil sampling test results.

Right away, the zone soil test results in Table 2 show some potential cut back on nitrogen and phosphorus rates in upper and lower SWAT MAPS zones. Zones 1-2 are hilltops where the yield is most limited by low moisture levels, whereas zones 7-10 start getting into yield-limiting levels of salinity. There are already higher soil nitrate and phosphate levels in these areas which will also influence the recommendation for these zones. The zone soil test also sheds some light on other soil factors that the composite sample does not show. The pH levels are elevated in zones 1-2 and 7-10, OM differences between zones are significant and sulfur and zinc levels in zone 1-4 are lower.

Fertility Recommendations

The process of making fertility recommendations based on a SWAT MAP is simply not a button to hit that gives a recommendation. Agronomists are in contact with the farmer early in the fall to discuss any fall fertilizer passes, and then again in the winter for spring plans. In some cases, the grower has a set fertilizer budget to work with, while other growers want a fertility plan more aligned with yield goals and soil test results. Once agronomists have the grower's intended fertility plan, VR recommendations can begin.

Soil test results (Table 2) are the main tool to determine crop demand for a certain yield goal. The soil test is also very useful in determining the soil N supply, including left-over nitrates, organic matter credits, and N credits for cases like previous pulse crops, broken up hay/alfalfa land or previous manure applications. A critical soil test N level of 20 lbs/ac is used. If levels are below this threshold at year end, the crop was potentially starved. If levels are higher than 20 lbs/ac, the crop was supplied with too much N, other factors limited yield and nutrient uptake, or the soil mineralized more nitrate in season that the crop didn't use. When making recommendations, the crop is supplied with enough N for the yield goal while maintaining the 20 lb/ac level at year end. N credits can be tricky as there aren't absolute numbers for the mineralization rate and amount of N coming from the organic matter, pulse crop residue, old hay residue, or manure applications. Organic matter credits can range from 6-8 lbs of N per % OM but can be unpredictable in terms of the above-mentioned practices. When making zone-based recommendations with N credits, the size of credit given can also be based on the landscape position of the field. Zones 1-2 usually have the lowest N credit per % OM as these areas tend to be driest, resulting in less mineralization. In Zones 3-8, credits gradually increase due to higher mineralization potential in lower landscape areas as soil moisture and organic matter content increases. Zones 9-10 can have the highest N credit unless poor health limits microbial activity.

**Figure 1. Nitrogen Recommendation for a 45 bu/ac average canola crop.**

The example SWAT MAPS Field in Figure 1 has soil nitrate levels of 15 lbs to 104 lbs. The zone trend is common, especially after drought years where the zone 1-2's (hills) and zone 7-10's (saline areas) both have high soil nitrate levels where the crop use was low. The organic matter levels range from 4.6 to 6%. The average canola yield goal for this field is 45 bu/ac; however, yield goals per zone do vary based on zone characteristics that limit yield potential. Canola is a heavy user of N, using roughly 3 lbs N per bushel of grain produced. Using the yield goals from Figure 1 would result in crop demand ranging from 105 lbs actual N to 150 lbs actual N. Crop demand is an easy starting point to begin making the recommendation. Total soil supply includes residual nitrates plus N credits from organic matter, minus any losses that may happen and minus the 20 lb/ac year end critical level. Losses are hard to predict but N losses in lower, saturated areas within a field due to denitrification are more likely to happen. There can be leaching losses in sandy areas as well with very wet conditions. Once soil supply is determined, this amount is subtracted from crop demand and the remaining fertilizer requirements are made into a VR report.

In a SWAT MAPS recommendation for P, 15 ppm Olden-P generally is the critical level. Less than 15 ppm is low and zone(s) testing low will receive higher P rates to increase the soil test P level to above 15 ppm. If the soil test level is higher than 15 ppm, maintenance rates are applied to the zone(s) to maintain the soil test levels above 15 ppm. If soil test levels are high, to a point where they become an environmental concern, lower P rates are applied to allow the crop to mine the excess P from the soil. In the SWAT MAPS field example, the soil test in Table 2 shows zones 3-6 are well below the critical level of 15 ppm. These areas are the focus for the VR phosphate application. Zones 1-2 and 7-10 soil test levels are above the critical level and will receive maintenance rates. Depending on yield limiting factors, lower P rates may be applied to allow the crop to mine from the soil. Saline areas and fields that have had excessive manure applications in the past are some examples of where mining soil P instead of maintaining the levels would occur. Table 3 has recommended application rates from AGVISE Laboratories for P based on soil test levels and yield goals. Canola is a heavy user of P, removing roughly 0.9 lbs of P₂O₅ per bushel of canola grown and this needs to be taken into consideration when making P recommendations for canola. The soil test results for the example field in Figure 2 are showing soil P levels down to 8 ppm. According to this recommendation chart and the yield goal, it would need to be 40-45 lbs of actual P₂O₅ just to maintain this soil test level; however, applying higher rates to build the soil P level is a good idea.

Table 3. Phosphorus fertilizer recommendation guide from Agvise Laboratories.

Figure 2 shows an example VR report of the N & P recommendations for the example field. As you can see, the fertility rates do vary significantly depending on zones, soil test data and the overall crop demand.

**Figure 2. Example VR report for SWAT MAPS field.**

Variable rate vs. Flat Rate Applications
You might be wondering how variable rate will give you the best ROI on your inputs and possibly save you some money. The soil test results from Table 1 and Table 2 would result in very different fertilizer applications. A recommendation based on the composite soil test would result in high application rates being applied to the whole field. The zone-based soil test is telling a different story, where there is opportunity to rely on residual N and P levels to supply the crop with part of the fertility demand along with accounting for yield limiting factors like the salinity in Zones 7-10. In Figures 3 and 4, variable rate vs flat rate urea comparison shows how effective SWAT MAPS can be at saving product from over application in areas of the field that don't need the extra fertility.

**Figure 3. Urea VR vs FR comparison for the example field.**

**Figure 4. Phosphorus VR vs. FR comparison for the example field.**

Conclusion
Composite soil testing is a good start when making fertilizer recommendations; however, this sampling method misses important details within areas of a field like nutrient levels, pH differences, salinity, organic matter, etc. Zone-based soil sampling and SWAT MAPS Variable Rate is the most effective way to capture all the variability within a field. In the variable rate vs. flat rate example, the grower would save 37,875 lbs of urea and 19,144 lbs of MAP just by using SWAT MAPS on this field. That is a large amount of product saved and can result in product reallocated to other fields or saved money that can be invested into other areas on the farm. Talk to your SWAT MAPS service provider about how they can help you get the best return on your crop inputs and save money with SWAT MAPS Variable Rate.

Kessler Ag Ventures on Doubling Their Client Base, ‘Aha’ Moments, and Achieving Sustainable Growth with SWAT MAPS

Kessler Ag Ventures (KAV) is well-known as Southern Saskatchewan’s team of precision ag experts. Comprised of five full-time employees, four of which are consulting agrologists, KAV has been providing SWAT MAPS services for over 10 years.

Doubling Their Client Base

“We started as an agronomy consulting business and then partnered with SWAT MAPS, which complimented our business very well,” says owner, Tyler Kessler. “We doubled our client base because of SWAT. We have the best map - it’s the only map we trust for doing variable-rate (VR) fertilizer, seed, and now VR herbicides. Clients are confident in the data and the integrity of map.”

Every farm operation KAV works with has a different story to tell, which is where good agronomy and good communication between growers and their staff comes in. “A SWAT MAP is the foundation layer to start that conversation with precision ag. Having this layer is a crucial piece to the entire precision ag system.” Kessler remarks.

When asked about his customers’ outlook on adopting VR technology, Kessler states, “There are clients who jump right in, and they can’t map their farm fast enough. When we come in with the SWAT MAP and they have previous maps, they want to convert those to SWAT MAPS. They see things from their previous maps that weren’t quite right, but the SWAT MAPS make sense to them because the soil properties are solid.”

As for the clients who are concerned with the adoption of new technology, Kessler comments that the KAV team can help remove that roadblock. Through their confidence with SWAT MAPS and ability to troubleshoot problems remotely, Kessler finds the process to be quite seamless for their team and their clients, which helps put their clients at ease.

‘Aha’ Moments

The Regina Plains area of Southern SK where KAV operates is known for their heavy clay topography. Kessler comments on two particular cases where SWAT was paramount in helping them understand the landscape and apply their findings to their VR recommendations.

Speaking of the variability of their ‘flat’ landscape, Kessler says, “Our land can look completely level but it does have depressions. When we have producers who are pushing the upper limits of yield, we need to be careful with our depressions. SWAT is a complimentary tool we can use to manage those risks. We can concentrate on getting more out of those higher zones and pushing that yield where possible while maintaining the depressions and not over-extending their maturity.”

Another ‘aha’ moment that Kessler likes to refer to when discussing how SWAT MAPS helped develop their knowledge of the landscape in relation to inverted electrical conductivity (EC); relating to soil erosion and movement of soil within a field.

“It can be shocking to see the EC layer showing something completely different than what we are physically standing on in the field,” remarks Kessler. “You come upon an eroded knoll and the SWAT MAP shows inverted EC, meaning that soil has moved into a depression. When you can explain to your growers what’s really going on and the map backs that up, that’s really valuable.”

Achieving Sustainable Growth with SWAT MAPS

KAV prides themselves on developing relationships with their clients to get an understanding of how each farm operates because they are all different. “There’s no cookie cutter recommendation,” says Kessler. “We offer a high level of service, very experienced staff, and we value every connection we’ve made within the network we’ve built over the past 10 years. I think that’s the recipe for success.”

Kessler acknowledges the environmental challenges across their trading area over the last 5 years. “It’s not super exciting to try new technology while experiencing multiple years of drought conditions. However, a SWAT MAP can be utilized to mitigate risk during these times when you factor in topography, EC changes and field variability.”

The KAV team has achieved a pattern of sustainable growth in their business over the last 10 years. “SWAT has been an important part to our sustainable growth” says Kessler. “With SWAT MAPS, we are able to offer our clients more data, resources, and information to grow their operations.”

The SWAT MAPS Team is proud to work alongside passionate, independent agronomy service providers like Kessler Ag Ventures. Learn more about their business and what’s happening in their corner by following them on social media or visiting their website and Twitter page.

Twitter: @KAVagronomy

Website: https://kesslerag.ca/

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

Service providers: Contact us for partnership opportunities.

Can we measure soil health?

Wes Anderson
VP of Agronomy
wes@swatmaps.com

Before we can answer the question “can we measure soil health?” we must first answer the question “what is a healthy soil?” And that isn’t a straight-forward answer. To those that ask, I would suggest reading Janzen et al. (2022) where a suggested definition is:

“Soil health is the vitality of a soil in sustaining the socio-ecological functions of its enfolding land.”

In other words, it depends. A healthy soil to grow rice may not be considered a healthy soil to grow potatoes or canola, as each crop or plant species prefers different physical or chemical attributes over others.

But for the sake of most broadacre crops that are cultivated in North America or Australia, there are some good guidelines to measure important soil attributes that lend to soil health, productivity, and resiliency in a broad range of weather conditions. The Soil Health Institute (SHI) has outlined three key measurements that are important:

Soil carbon concentration – related to the more commonly tested “organic matter percent”, organic carbon promotes better soil structure, microbial activity that cycles nutrients, and soil water holding capacity.
Carbon mineralization potential (CO₂ burst) – an indicator of microbial activity that cycles carbon and nutrients.
Aggregate stability – a measure of soil structure that is important for water infiltration, storage, and ability for plant roots to access water and nutrients.

More robust regional models have also been developed, such as the CASH score (Moebius-Clune et al., 2016) and SASH score (Wu and Congreves, 2021) that confirm the importance of the tests outlined by the SHI, as well as some others such as standard nutrient extractions and ACE Protein (autoclave-citrate-extractable protein). More recently, Zhang et al. (2024) found similar indicators in a robust study utilizing long-term crop rotation experiments at the Breton Farm in Alberta, Canada. This study also identified ACE Protein as a key indicator of soil health. Furthermore, in Michigan, USA, Naasko et al. (2024) found ACE Protein to be a useful indicator of soil health with a strong link to yield. So, what is ACE protein and why is it such a common indicator of soil health?

ACE protein can be thought of as a measure of soil organic nitrogen that is readily mineralizable. It’s part of the dead organisms in the soil that are decomposing and ready to supply nutrients to a growing crop – which is what we typically want functional, healthy soil to do during the growing season.

Unfortunately, the ACE protein test is currently quite expensive, although there is some work being done at University of Saskatchewan (Wu et al., 2023) to make it more scalable and affordable for commercial labs to routinely test. Regardless, at Croptimistic we dedicate resources every season to better understand emerging technologies that can enhance the value of SWAT MAPS and our knowledge of soil function across the landscape. Through testing of five management zones in 24 different fields, we have also found ACE protein to consistently represent much of what we know about soils in different SWAT zones and in different fields.

Our first interest was general trends by SWAT zone. What we found was a fairly consistent trend of increasing ACE protein values from zone 1 to zone 8, often mirroring organic matter (OM) levels and long-term productivity related to water and nutrient availability. Samples from zones 9-10 had a high degree of variance though (Figure 1), related to both OM and soil test electrical conductivity values (EC; measure of salts).

*Figure 1. ACE Protein levels by SWAT zone in a wide range of soils across western Canada. Very high outlier points in zones 7-10 were from fields with peat soils.*

Further analysis of the data showed interesting trends associated with both OM and EC, where high EC soils affected by salts had low ACE protein levels relative to the OM level (Figure 2). This would indicate that despite having high OM, salinity will reduce the ACE protein level compared to a non-saline soil. There was even a tendency for very well-drained, low EC soils (< 0.5) having relatively high ACE protein levels compared to other non-saline soils with slightly higher EC.

*Figure 2. ACE protein relationship with OM and EC in multiple fields across western Canada.*

On a management zone level, where management decisions take place using SWAT, these broader trends were confirmed. For example, Field “A” had some poorly drained soils and increasing salinity in zones 7-10, while Field “B” had increasing OM from zones 1-10 with zone 10 being a very high OM peat soil type. These peat soils are known to have exceptional capacity for nitrogen and sulfur mineralization in-season, provided the soil has plant-available water to maintain microbial activity.

*Figure 3. ACE Protein levels by SWAT zone on two different fields.*

What we found:

While the ACE Protein test is only one indicator of soil health, it did prove to be more valuable than other tests we’ve tried, as it was sensitive to multiple soil properties like OM and salinity, as well as some crop history (data not shown).
ACE Protein adds another layer of depth to mineralization estimates beyond just OM, the current industry standard.
There were clear and logical differences between SWAT zones, indicating measurable soil health does significantly vary across most landscapes.

So what?

It appears some additional tests such as ACE protein can give us a better indication of soil function that could lead to better fertilizer recommendations, such as where nitrogen rates could be reduced without affecting yield potential. While it’s not a test that needs to be done every year as it is relatively expensive and should only be used with purpose, the ACE protein test is more sensitive to management changes than organic matter tests, and as a result could be used to measure the differences in soil due to changes in tillage or crop rotation, for example (Sainju, et al., 2022; Naasko et al., 2023).

The results also highlight the importance of proper soil drainage and understanding the limiting factor for yield. If parts of the field are poorly drained and salinity becomes a problem, it effectively trumps everything else. It won’t matter how high the OM is, or that there are ample nutrients available. The salts will affect plant-available water and limit biological function. This is why each test we can perform on a soil must be considered holistically with other tests, in the context of the environment it is in, and for the function the soil is supporting (such as crop species).

Soil health is a large, ambiguous topic. While it is not easily defined, not to mention measured, there are some emerging laboratory tests that show promise in adding additional information to what we already have with SWAT MAPS and regular soil lab tests. The combination of this type of data along with standard nutrient extractions and pH can help guide the accuracy of variable rate applications of nutrients even further, benefiting farm economics and the environment.

References:

Janzen, H. H., Janzen, D. W., & Gregorich, E. G. (2021). The ‘soil health’ metaphor: illuminating or illusory? Soil Biology and Biochemistry, 159, 108167.

Moebius-Clune, B.N., D.J. Moebius-Clune, B.K. Gugino, O.J. Idowu, R.R. Schindelbeck, A.J. Ristow, H.M. van Es, J.E. Thies, H.A. Shayler, M.B. McBride, K.S.M Kurtz, D.W. Wolfe, and G.S. Abawi. (2016). Comprehensive Assessment of Soil Health – The Cornell Framework, Edition 3.2, Cornell University, Geneva, NY.

Naasko, K., Martin, T., Mammana, C., Murray, J., Mann, M., & Sprunger, C. (2024). Soil protein: A key indicator of soil health and nitrogen management. Soil Science Society of America Journal, 88(1), 89-108.

Sainju, U. M., Liptzin, D., & Stevens, W. B. (2022). Autoclaved citrate-extractable protein as a soil health indicator relates to soil properties and crop production. Nutrient Cycling in Agroecosystems, 124(3), 315-333.

Qianyi Wu, Kate A. Congreves, and Richard E. Farrell. (2023). Microwave-assisted citrate extraction (MaCE) as an alternative to autoclave citrate extraction (ACE) of a soil protein fraction. Canadian Journal of Soil Science. 103(4): 684-688.

Wu, Q., & Congreves, K. A. (2021). A soil health scoring framework for arable cropping systems in Saskatchewan, Canada. Canadian Journal of Soil Science, 102(2), 341-358.

Zhang, J., Dyck, M., Quideau, S. A., & Norris, C. E. (2024). Assessment of soil health and identification of key soil health indicators for five long-term crop rotations with varying fertility management. Geoderma, 443, 116836.

Building Soil P Levels

Hana Ruf
Regional Manager, East Central SK
hana@swatmaps.com

Producers in Western Canada may be leaving yield on the table by not addressing low phosphorous soil levels. Many fields in Western Canada are low in soil phosphorus levels (below 15 to 20 ppm). Phosphorous removal rates not being replaced is one of the reasons for this. Through years of testing with SWAT Zones, general trends within a field landscape have been identified. In 2023, 75% of SWAT MAP zones tested for phosphorous were below 20 ppm (Figure 1).

Current P Levels in Western Canada

Figure 1. Olsen-P ppm (0-8”) by soil test category and SWAT zone taken from all SWAT MAP fields, fall 2023.

Phosphorus variability is driven by erosion — moving downslope with soil — as well as crop removal. A field’s history often determines the trend, but typically zones 9-10 (lowest, wettest, most saline areas) are highest in P and zones 1-2 (highest, driest areas) are lowest, such as inFigure 2. A common outlier for this trend is when there is minimal historical erosion and P removal in zones 1-2, causing P levels to be higher in zones 1-2 and lower in zones 3-6 where P removal has been high over the years such as in the Dark Grey and Grey Soil Zones in Figure 2.

Figure 2. Soil test P levels (0-8”) by SWAT zone and Soil Zone from Saskatchewan, Manitoba, and Alberta fall 2023.

Approximately 40 to 60 lbs P₂O₅ are removed annually in a canola-wheat rotation (Table 1). If what is applied annually is being removed in the same year, P is mined from the soil. This is why we see so many fields with overall low P levels that have had annual high yields being removed. If a canola crop yields 55 bu/ac and 35 lb/ac P₂O₅ was applied, the crop is mining about 8 lb/ac of P₂O₅ from the soil. Repeated over many years, the soil is left with low P levels despite having good yields in previous years. Eventually, yields will start to decline as a result.

Table 1. Field crop nutrient uptake an removal. Manitoba Soil Fertility Guide, 2007.

How much yield is being left on the table?

A three-year study was conducted by the University of Minnesota comparing corn and soybean response to annual applied P in low (4 to7 ppm) and high (15 to 20 ppm) available P soils. Trials were done with rates of 0 lbs/ac P₂O₅, 25 lbs/ac P₂O₅, and 50 lbs/ac P₂O₅. Corn and soybean responded well to both applied fertilizer rates on the low testing P soils, with the best response from the higher P₂O₅ rate. There was no significant response to P on the high P soil but overall, it had higher yield compared to the applied rates on the low available P soils, and the gap was significant. The corn yield for the high P soil where 0 lbs/ac P was applied yielded 25 bu/ac more than the highest yielding corn on the low P soil. This is not to say you would want to apply zero rates when soil levels are at 15 to 20 ppm as the crop would then be drawing from those levels. Instead, you would want to apply maintenance rates by meeting the removal rates for each year’s crop.

Figure 3. Results from a 3-year study at University of Minnesota on corn and soybean response to annual fertilizer rates on low P soil and high P soil.

Adam Gurr with Agritruth Research Inc. near Brandon, MB has done extensive research demonstrating the benefits of building soil P. A trial has been conducted every year since 2018 to evaluate the immediate and long-term benefits of building soil P with a big one-time application of 11-52-0 (MAP). The trial application rates are a standard check (0 lbs/ac MAP), 700 lbs/ac MAP, 350 lbs/ac MAP, and variable rate (VR) MAP at an average of 260 lbs/ac MAP) and replicated four times. This past year in 2023 the crop was wheat. The standard (0 lbs/ac) trial yielded 118.6 bu/ac, the 350 lbs/ac trial yielded 124.9 bu/ac, the 700 lbs/ac trial yielded 125.5 bu/ac, and the VR MAP trial yielded 127.5 lbs/ac.

The most impressive aspect of these trials is the long-term ROI for the VR applied MAP due to the reduction in cost. Most years it compared in yield to the 350 lbs/ac MAP and 700 lbs/ac MAP, but less MAP was needed to achieve those results.

Table 2. Long-term effects of high P build from 2018-2023 done by Agritruth Research Inc. in Manitoba.

Crop	Year		standard	700lbs	350lbs	VR MAP	LSD	CV
Wheat	2018	Yield (bus/ac)	85.1 (C)	103.8 (A)	98.7 (B)	95.5 (B)	5.0	4.0
		Protein (%)	13.2 (A)	12.7 (B)	13 (AB)	12.8 (B)	0.4	2.3
Canola	2019	Yield (bus/ac)	60.7 (B)	64.8 (A)	63.6 (AB)	64.6 (A)	3.3	4.1
Wheat	2020	Yield (bus/ac)	59.5 (B)	62.1 (A)	60.9 (AB)	61.3 (A)	1.6	2.0
		Protein (%)	15.2 (A)	14.6 (C)	14.9 (B)	15 (AB)	0.3	1.4
canola	2021	Yield (bus/ac)	48.2 (B)	51.9 (A)	50.7 (A)	50.5 (B)	2.4	3.6
soybeans	2022	Yield (bus/ac)	61.1 (AB)	62.8 (A)	60.6 (B)	62.3 (AB)	1.6	2.0
wheat	2023	Yield (bus/ac)	118.6(B)	125.5 (A)	124.9 (A)	127.5 (A)	4.3	2.7
		Protein (%)	13.3 (A)	13.0 (B)	13.1 (B)	13.0 (B)	0.2	1.4

Table 3. Long-term ROI after one-time P builds in 2018. Agritruth Research Inc., Manitoba.

	standard	700lbs	350lbs	VR MAP
Total lbs of P applied	0	364	182	140
Total revenue	$4,979.00	$5,320.97	$5,203.05	$5,249.06
revenue difference to standard	$0.00	$341.97	$224.05	$270.06
cost of treatment	$0.00	$172.43	$86.21	$66.31
6 year ROI	0	198%	260%	407%

The reason the VR applied P build works best? A look back at Figure 2 can show the answer. Typically, there are zones in a field that already have adequate to high P levels. Since other zones in the field may be very low in P and require 200+ lbs/ac, it would not be economical to flat rate these rates across the entire field and apply it in zones requiring less or no P due to high soil P levels. We especially do not want to overapply in areas where there is high salinity and low yield potential as we would be wasting a significant amount of money in those zones. Using VR to apply these high P rates usually results in the highest yields in these trials because we can be precise about putting the right amount of product in the right places within the field. Not only is this a more economical approach, but it’s also an environmentally conscious approach as well.

In a 3-year study done by Northeast Agriculture Research Foundation (NARF) in northern Saskatchewan, a high P build trial was done using SWAT MAPS variable rate. Soil P ranged from 4-5 ppm in zones 1-6 to 19-29 ppm in zones 7-10. Results can be seen in Table 4 below.

Table 4. Results from a 3-year P build study using SWAT MAPS.

Field	Treatment	Year	Crop	P Build Grain Yield (bu/ac)	No P Build Grain Yield (bu/ac)
1	200 lb/ac MAP, applied in 4 strips	2013	Wheat	43.6	41.2
		2014	Canola	54.6	51.9
2	150 lb/ac MAP, applied in 2 strips	2013	Canola	Nd	Nd
		2014	Fababean	59.5	52.0
3	300 lb/ac MAP, applied in 1 strip	2013	Canola	46.6	42.0
		2014	Barley	91.2	83.9
		2015	Canola	65.9	59.9

The results of this study show an increase in yield in subsequent years after applying the high rate phos build. After the soil P levels are brought up to 15 to-20 ppm, if maintenance application rates are being met, this should continue to be the case.

How to Build Soil P

Approximately 20 lbs/ac P₂O₅ is needed to increase soil test P by 1 ppm. This means you would need to apply 70 lb/ac P₂O₅ for a 50 bu/ac canola crop just to increase the soil P by 1 ppm. However, most soils need a lot more than this. The most economical and efficient way to build soil P is to pick a field or a few fields each year to do a big, one-time build to get the levels up to 15 to20 ppm. After that, apply maintenance rates. If very high rates are needed, split the application over a two-year period to spread out costs. However, to do an overall increase over an entire farm likely is less feasible as it will require handling a lot more P at seeding time and will be a much slower increase, so the return isn’t as quick. The lower the soil P levels, the more crops will respond to applying high enough rates to get levels up to 15 to 20 ppm, as shown in Figure 4.

Figure 4. Response to annual seed placed P₂O₅ on wheat yields with various increasing soil P.

Figure 5. SWAT MAPS VR report demonstrating an applied P build using an MESZ/MAP/Potash blend.

Figure 5 shows an example of a SWAT MAPS VR report where a one-time P build was applied. In this case, a MESZ/MAP/MOP blend was applied. MESZ was added to ensure the high P levels and high soil pH do not induce a zinc deficiency in susceptible crops grown on the farm, such as corn, wheat, and barley. Straight MESZ was not used as there was a price premium and higher rates were needed to reach the overall actual P goal.

Applying these high P build rates are best if banded into the soil as deep as possible. If the phosphorous is spread on the soil surface, ensure it is incorporated with tillage immediately after application. Application timing can be done in fall or spring.

Summary

Soils with low P levels are limiting yield. Over the years, P levels have decreased on many fields due to erosion and high removal rates. Using SWAT MAPS variable rate is a cost-effective way to build soil P levels to support higher yields.

References

Gurr, A. (2019). Long-term P trial 2019. agritruth.ca.

Leikam, D., G. Randall and A. Mallarino. 2010. Are current soil test-based phosphorus and potassium recommendations adequate? Crops & Soils. Vol.43-6. Pp 27-32.

Manitoba Soil Fertility Guide. (2007). Government of Manitoba. https://www.gov.mb.ca/agriculture/crops/soil-fertility/soil-fertility-guide/pubs/soil_fertility_guide.pdf

Stewart, B. (n.d.). Revisiting Phosphorous Recommendations. Agriarm. https://agriarm.ca/wp-content/uploads/2017/01/Revisiting-Phosphorus-Recommendations-Stu-Brandt.pdf

Wager, B.I., J.W.B. Stewart, and J.L. Henry. 1986. Comparison of single large broadcast and small annual seed-placed phosphorus treatments on yield and phosphorus and zinc contents of wheat on Chernozemic soils. Can J. Soil Sci. 66:237-248.

CROPTIMISTIC RELEASES INAUGURAL SUSTAINABILITY REPORT

SASKATOON, SK, CANADA – MAR 1, 2024: Croptimistic Technology Inc. (Croptimistic) is proud to release their inaugural Sustainability Report. The report outlines the 2023 sustainability achievements and future aspirations within the company. Croptimistic says it “is showing leadership by serving our society, serving our people, employing responsible business practices, and championing environmental stewardship.”

Croptimistic is a global ag tech company best known for their flagship product SWAT MAPS (Soil, Water and Topography Maps), which enable farmers to execute soil and crop practices with precision, in order to minimize environmental impacts, optimize production of food, and improve profitability. The company is continually releasing new products that have zero greenhouse gas emissions such as the SWAT CAM, a fully automated plant stand counting system that uses artificial intelligence to collect millions of data points per farm.

“We built our sustainability strategy around our impacts. We evaluated what we were doing well, what we could do better, and summarized what we did in 2023,“ says Bonnie Dobchuk, Sustainability Director. “A sustainable business solves the problems of both people and planet in a profitable way. When we solve a problem, we make an impact. That is exactly what we do at Croptimistic.” Dobchuk adds, “With a focus on agricultural sustainability and rural community impacts, Croptimistic’s sustainability impacts align with the Sustainable Development Goals of SDG2 – Zero Hunger, SDG15 – Life on Land, SDG3 – Good Health and Well-being, and SDG8 – Decent Work and Economic Growth. This was done using impact materiality as guided by the Global Reporting Initiative.”

“Farm sustainability is increasingly being challenged by the broader public,“ says Wes Anderson, VP of Agronomy at Croptimistic. “SWAT MAPS service providers and farmers are achieving major environmental sustainability impacts and our white paper on The Role of SWAT MAPS in Environmental Stewardship outlines these clearly. If farms are utilizing these practices on all of their acres, they become SWAT CERTIFIED and will receive our new Advanced 4R Report that validates they are surpassing global application standards.”

Greg Stewart, Chairman of the Board for Croptimistic and Director at the Bank of Canada adds, “With a steadfast commitment to sustainability ingrained in every aspect of their operations, Croptimistic sets a gold standard for environmentally conscious practices within the agricultural industry.”

Cory Willness, CEO of Croptimistic adds “We are very pleased to play a small part in the incredible success that farmers utilizing SWAT MAPS are accomplishing in environmental sustainability.”

The 2023 Croptimistic Sustainability Report is available for viewing online at swatmaps.com. Those who wish to receive a hard copy can request one by contacting support@swatmaps.com.

About Croptimistic Technology Inc.: Croptimistic’s vision is to the be the global leader in premium precision agriculture services. It is an international ag tech company providing SWAT MAPS, a turn-key variable rate process that combines Soil, Water, and Topography factors of fields for the creation of precision management zones and prescriptions. Their SWAT RECORDS software powers the entire SWAT ECOSYSTEM of products that are synced with the app for real-time viewing. Their growing network of service providers and farmers are utilizing SWAT MAPS annually on 3.4 million acres in 4 countries. Impressive technology, an expanding service provider network and 98% retention of acres year over year showcase the validation that farmers are seeing value from this premium precision agriculture service. Learn more about SWAT MAPS by visiting swatmaps.com.

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For more information, contact:

Alexandra Blackwell

Marketing Coordinator

marketing@swatmaps.com

Managing Drought with SWAT MAPS

Jill Sparrow
Senior Precision Agronomist

Farmers across many areas of Western Canada are all too familiar with the dry cycle of the past few years. Driving through these areas in mid summer, burnt up fields with “pothole” green depressions is a common sight. There are a lot of risks associated with farming, with Mother Nature being the biggest uncontrollable risk to every operation. A crop can only be as productive as the amount of water available to it. There are multiple ways to manage the risk of dry conditions which include the use of crop insurance, timing of seeding, weed management, stubble management, etc.

*Figure 1: Photo of wheat crop in mid July of 2023. Hills are burnt up, mid-slopes are starting to turn, depressions are thick and green.*

One mitigation approach could be switching up fertilizer strategies – the crop didn’t take up all fertilizer from last year and probably won’t use the same as usual, so hey let’s cut back. Easy. Done. Right? Yes… but what if you could take that one step further? What if the correct variable rate program can help you mitigate this risk on yet another dry year?

Using SWAT MAPS, you can allocate fertilizer based on the potential each area of the field has to further mitigate the risk of drought. The fertilizer on those hills and maybe even mid-slopes probably should be cut back but those “pothole” green depressions still have the potential to grow a decent crop in a dry year. SWAT MAPS can put your fertilizer where it counts.

Capturing the Right Variability in a VR Map

Although weather and dry conditions influence a crop and its yields, the right variable rate (VR) maps shouldn’t capture all field variability. After all, a hilltop that yields the same as a saline depression, but for different reasons, should not be treated the same. To create the correct base for a VR program, VR maps need to focus on soil potential and fertilizer-based response versus yield potential; Soil, Water, and Topography (SWAT) MAPS do this. SWAT MAPS separate fields into zones based on soil characteristics to help farmers allocate fertilizer where it is most needed.

Flat rate vs VR Fertilizer

Using variable rate doesn’t necessarily mean cutting fertilizer rates by a certain percentage across an entire field, but VR through SWAT MAPS can still get a higher return on investment on clients applied nutrients. This is done by taking an existing fertilizer budget and reallocating that money to areas of the field that will respond more. In drought conditions, we are more aggressively cutting back fertilizer, particularly nitrogen, on low moisture, low potential areas. We are then taking that fertilizer and putting it in the areas with more moisture and therefore more response potential. This is seen in an example report below. Of course, we are also deciding on rates based off soil trends, mineralization potential, nutrient levels, farm logistics, etc. At the end of the day, you are spending money on fertilizer already; why not put that budget into the right spots?

*Figure 3: Example VR Report for Drought Conditions*

Summary

Croptimistic takes pride on the many benefits and values of SWAT MAPS. In an area with ample moisture, even maturity might be the driving benefit for variable rate. But, in a dry area, risk management most likely is the overall VR goal. The hills are going to burn up quick and we don’t want to fertilize so your yield bearing areas do the same. Managing risk is done by reallocating fertilizer to areas of the field that have the best opportunity for higher yields and scaling back on areas of the field that do not. It is no coincidence that the “W” in SWAT MAPS stands for water. And after all, water is the biggest driver of yield and fertilizer response.

*Figure 4: Same Field, Different SWAT zones. Mid July 2023.*

Now is the time to plan your fertilizer strategy for the 2024 season.

Book your acres for spring by visiting our Book a Demo page.

Effect of residual nitrate on N-fixation in pulse crops – will too much N hinder or help?

Lara de Moissac
Precision Agronomist
lara.demoissac@swatmaps.com

Drought in parts of the Prairies and Northern Great Plains has affected crop growth at various stages of the past year. Yields ranged from average to mediocre to less than ideal, to put it gently. Along with growing conditions being variable, so are soil nitrate levels after a round of soil testing. When a pulse crop is in the rotation, it’s worth looking at these soil nitrate test results to assess how much N is available. If there’s too much N, it’s worth putting another crop on that field and use the ability of pulses to fix their own N on a field with less residual N. We want to take advantage of the N-sparing effect pulse crops offer. But what happens if there’s too much residual nitrate? Will pulse crops even initiate nodulation?

First, it might be helpful to review the process of nodulation initiation and how the crop receives N from an effective nodule. It begins by pulse crop roots releasing molecular signals to rhizobia in the rhizosphere to infect the plant’s root hairs. Close contact between bacteria and the root hair is necessary for an attachment to occur. Then, rhizobia respond by secreting a compound that activates root hair deformation, or the beginning of nodules in roots. After the nodule is formed and all the necessary conditions are met, rhizobia supply usable ammonium ions for protein production in the plant, in exchange for energy supply in the form of carbohydrates. That’s the process in a nutshell, although there are many more steps between signaling and N-fixation. If there are high enough levels of nitrate in soil, pulse crops will use that form of N instead of initiating nodulation by sending out the molecular signal.

Here's a RealAgriculture Pulse School interview that highlights the importance of soil sampling after drought years.

How much is too much?

Overall nitrogen fixation by pulse crops is known to be affected by mineral N availability in the soil (Voisin et al., 2003) and studies in Saskatchewan and Manitoba with lentils and soybeans, respectively, have shown varying results. Lentil yield was not affected by 80 lbs/ac N, if inoculant was used (Bremer et al. 1988) and although not directly tested on peas, could serve as a general guideline. Nitrogen fixation is also known to vary during the growth cycle of pulse crops; early growth is sustained by the N content in such large seeds, but that N can be exhausted before nitrogen fixation is initiated — which begs the question, is there enough N for the crop between seed N depletion, and when N-fixation begins if an inoculant is not used, or the field has no or low background levels of rhizobia?

How can soil sampling by zone help?

*Table 1. SWAT MAPS zone-based soil nitrate test results (lbs/ac) from 0 to 8" in the Dark Brown Soil Zone of southern Alberta from fall of 2021, 2022, and 2023.*

Using a general rule of 50 lbs/ac as the level at which pulse crop N-fixation will be delayed or hindered, about 60 percent and 46 percent of the example field in Table 1 would have residual nitrate levels that exceed the guideline for a pulse crop planted in spring of 2022 and 2023, respectively. If a composite sampling plan were used for this field in 2021, the average nitrate level of 33 lb/ac would be misleading, as much of the field is above 50 lb/ac. For spring of 2024, this field has suitably low residual nitrate levels to plant a pulse crop and still maintain an N-sparing effect. SWAT MAPS zone-based sampling helps determine both high and low residual nitrate levels by zone and delineates how much of the field is above the proposed threshold. As a planning tool for next year’s crops, knowing the area of a field that has residual N above the proposed threshold is beneficial.

References:

Bremer, E., R.J. Rennie, and D.A. Rennie. 1988. Dinitrogen fixation of lentil, field pea and fababean under dryland conditions. Can. J. Soil Sci. 68: 553–562.

Voisin, A.S., C. Salon, C. Jeudy, and F.R. Warembourg. 2003. Root and nodule growth in Pisum sativum L. in relation to photosynthesis: analysis using 13C-labelling. Ann. Bot. 92: 557–563.

manitoba.ca
manitobapulse.ca
landresources.montana.edu

Including soil texture in a proactive approach to micronutrient deficiencies

Lara de Moissac
Precision Agronomist
lara.demoissac@swatmaps.com

On the Prairies, micronutrients such as copper (Cu) and zinc (Zn) are variable in their distribution of total and available amounts across landscapes and fields, and because of this, site- and crop-specific management is required.

Soil extractions for testing plant-available micronutrients are a good start to determining deficiency levels and for pinpointing areas of fields that may need a micronutrient top-up. However, a soil extraction sometimes does not extract all the nutrient because the nutrient is bound in unavailable chemical fractions in the soil or has transformed into a different chemical species. Due to this, the ppm of micronutrients can be thought of more like guidelines and a reactive approach is often taken to mitigating deficiencies with in-season foliar micronutrient applications.

Leached, acidic, or sandy soils are low in most micronutrients for the same reason they’re low in macronutrients; the parent materials were generally low in nutrient elements to begin with. In the case of organic soils, micronutrient content depends on the extent of leaching.

In mineral soils, micronutrient deficiency usually occurs in coarse-textured soils containing low organic matter (e.g. Grey Luvisolic and Grey Black transitional soils). Organic or peaty soils are also susceptible to deficiency and are often highly responsive to Cu fertilization due to low mineral content, as is the case in central and northern Alberta and Saskatchewan and central Manitoba. In high pH and high calcium carbonate-containing soils, surface adsorption of Cu and Zn are promoted, therefore reducing their availability to plants.

So, what if a more proactive approach to micronutrient deficiencies could be taken by using soil texture to predict shortages, in addition to soil testing, tissue testing, crop yield, and nutrient removal?

Recent research out of the University of Saskatchewan by Rahman et al. (2021) examined how soil texture as well as other soil properties, could help predict micronutrient deficiencies. More specifically, their study found that high sand content and low organic matter were identified as important soil properties that contributed to Cu, Zn, and B deficiency.

This theory has merit from the perspective of soil texture, because of sand’s inability to hold on to nutrients due to a lack of cation exchange sites and generally lower organic matter, that a higher clay content soil would have. (See the negative influence of sand on availability of micronutrients in the table below from IPNI)

Table 1. Influence of environment and soil conditions on micronutrients

Furthermore, among the soil attributes measured in Rahman et al.’s study, soil carbon and sand content appeared to be the most important in controlling the distribution of micronutrients among different soil pools, based on specific solubility ranges.

Researchers in Alberta established that the distribution of Cu through the soil profile is more important than surface soil values for determining the probability of a deficiency in a crop (Penny et al., 1992), which highlights the importance of thinking in 3D when it comes to soils.

The mechanisms behind Zn deficiency symptoms showed up in fields in the Wadena and Archerwill, SK areas — areas with high sand and low organic matter content. The soil pH of both these fields in the 0 to 8” depths was around 8 and 8.1, respectively, and Figure 3 shows how sandy the field at Archerwill was (in addition to soil testing from the previous fall).

*Figure 1. Zn deficiency on high pH, high sand content soil near Wadena, SK, Brandon Smith.*

*Figure 2. Tissue test results showing low Zn near Wadena, SK, Brandon Smith.*

*Figure 3. Soil core from the Archerwill, SK area where Zn deficiency symptoms showed, Jill Sparrow.*

*Figure 4. Symptoms of Zn deficiency in wheat near Archerwill, SK, Jill Sparrow.*

When it comes to micronutrient diagnosis, the most conclusive approach still involves soil and tissue testing, as well as implementing some test strips. The patchy nature of micronutrient deficiencies make them a good candidate for variable rate prescriptions through the SWAT MAPS ECOSYSTEM, as the deficient areas can be targeted with a high-resolution prescription.