1. 11th International Drainage Symposium, Des Moines, Iowa
September 1, 2022
Beneficial Practices for Soil and Water Management
in Undulating Soils in Southwestern Manitoba
AN APPLIED RESEARCH AND DEMONSTRATION PROJECT
Financial support provided by:
Project led by:
In cooperation with: In-kind support from:
2. Agenda 1. Project overview & regional context
2. Research site layout & design
3. Preliminary results
4. Next steps
4. Why this
Undulating landscapes in southwestern Manitoba:
prone to excess water and droughtiness
significant salinity limitations – common and worsening
Agricultural water management in the region:
surface drainage is common-place
tile drainage is emerging as a significant practice
Gaps in knowledge in BMPs for tile drainage in this
region of cold climates and complex topography
5. Primary objectives
Evaluate soil and water BMPs in the cold climate and complex
reduce nitrogen, phosphorus and salt export in runoff
reduce excess water and improve drought resiliency
Develop a demonstration site for knowledge transfer for soil
and water BMPs
6. Regional context
Productive, Black soil zone
Average annual temp. 2.5◦C
Annual precip. 508 mm [20.0 in] (~25% as snow)
Spring runoff when soils are frozen!
Growing season (May – Aug) precip. 246 mm [9.7 in]
20. 2023 and
Tile drainage water quality treatment
Modeling using Drainmod-S
long-term trends in hydrology and salinity
Complete analysis and reporting
I am happy to have the opportunity to share with you today some information about our applied research and demonstration project evaluating soil and water BMPs in southwestern Manitoba, Canada.
The project is being led by myself, David Whetter, with AgriEarth Consulting Ltd., along with Bruce Shewfelt of PBS Water Engineering Ltd.
We are grateful to the Canadian Agricultural Partnership, MB Crop Alliance, MB Canola Growers and MB Pulse and Soybean Growers for funding this project.
We would also like to thank our cooperating producer, Whetter Farms Ltd., as well as Souris River Watershed District and AgriDrain Corporation for in-kind support.
For the presentation today I will provide a brief project overview and some regional context, followed by an overview of our research site design and some methodology.
I will then share some preliminary results from the 2022 season to date
And I will wrap up with some comments on next steps.
So, why this project?
First, the undulating landscapes across the southwestern region of Manitoba are prone to excess water and droughtiness, which can both act to significantly limit crop productivity not just across growing seasons, but within them as well. So this is a real challenge for producers.
Salinity is another significant limitation, and is typically associated with shallow water tables. It is an issue which is exacerbated by the shift from permanent grassland to annual cropping, so it’s been getting worse over time in cropping fields!
Surface drainage has long been practiced in the region. However, in the last few years tile drainage is emerging as a significant land improvement practice.
The emergence of tile coupled with gaps in knowledge in beneficial management practices for tile drainage in the cold climates and complex topography in the region is really driving the need for projects such as this.
So, the primary objectives of this project are to:
1. Evaluate BMPs in the cold climate and complex topography context. Specifically, those that:
reduce nutrient and salt export in agricultural runoff
reduce excess water and improve drought resiliency
2. Develop a demonstration site for knowledge transfer to industry, namely contractors and producers.
The site is located in the southwestern corner of Manitoba, just north of Minot, North Dakota. It is located in the Black Chernozemic soil zone of the Prairies region.
The study site is characteristic of this broad region of undulating landscapes, where excess moisture, drought and salinity are all significant limitations to crop productivity.
In terms of climate, the region has an annual temperature of 2.5C. This is significant as our soils are frozen for a good portion of the year (typically, December through March or April).
We receive just over 500 mm (20 in) of precipitation, 25% of which falls as snow. Spring runoff typically occurs when soils are frozen so much of the spring melt runs off the field.
During the growing season from May to August, the area receives around 250 mm or close to 10 in of rainfall.
I will shift gears now and provide an overview of the research site layout and design, and will touch on the monitoring program.
The site design includes a “commercial” tile system across the field (3 discrete zones in grey shading), and field-scale research plots (labelled Plot A and Plot B).
The site-specific design comprises half of the 320 ac field.
The system was installed in Fall 2021 so this is the first year in operation. The system was designed for a 1/4/day drainage coefficient and tiles are on 50 ft spacings.
I will now zoom into the northwestern or upper-left portion of the field to take a look at the research plots.
We have two tile drainage research plots that are really field-scale systems.
Plot A is just under 19 ac in size, while Plot B is just under 7 ac in size.
The plots have lateral lines installed on the contour, with pairs of tiles collecting in discrete outlets. The shading represents discrete soil-slope associations – darker shading is the Upper-Mid position, the moderate shading is the Lower-Mid position and the light shading is the Lower position.
The plots are replicated in that they comprise similar soil-slope associations.
This design allows us to monitor tile flow and water quality from the different landscape positions.
Transect based monitoring is established with a transect in each plot – the dashed lines and green circles represent transects and monitoring locations.
This allows for real time monitoring of depth to water table at each soil-slope position, as well as soil moisture at multiple depth to 120 cm.
Monitoring transects also include an undrained UPPER position as well as an undrained DEPRESSIONAL position.
This provides an oblique aerial image showing the field from the northwest corner where runoff outlets through a culvert.
You can see the approximate locations of the field drainage zones, the two research plots and the monitoring transects.
The undulating topography has approximately 2-3% slope gradients. A major surface drain (in blue arrows) runs through the field from the southeast to the northwest corner. There remain some closed surface depressions in the field.
Soils are predominantly loam to clay loam in texture. And salinity is a an issue as you can see in the low-lying area in the foreground.
These are hot off the press and data analysis is still in process, but I’m happy to share some interesting, preliminary results.
I will take you through some samples of data we have processed for soil moisture, water tables, tile flow and water quality.
Results are limited to Plot A only, in the interest of time.
This diagram represents a cross-section of the monitoring transect for Plot A, with the ground surface represented by the black line.
From the Upper position (A-UPP) to the Lower position (A-LOW), there is 2.7 m or 9 ft of relief.
Tiles, represented by the black circles are installed at approximately 1 m (or just over 3 ft). The Upper position is not tile drained.
The water table is shown by dashed lines for 3 dates:
green dashed shows July 3 with the water table at tile depth in lower locations
2.2 inch rainfall fell between July 3rd and 4th
dramatic rise in water table on July 4 represented by the blue line, water table close to surface at lower positions.
By July 7 in the orange line, water table has fallen significantly as the tiles were doing there work.
UPPER also fell presumably due to lateral, downslope movement
We would expect that had tile not been installed that this event would have caused significant impact to the crop rooting zone in the lower positions
Here is a chart showing the water table depth below ground (on the left axis) at the undrained Upper position (black), upper-mid position (blue), lower-mid position (fuscia) and lower position (gold).
Precipitation events are shown in the grey bars – you can see there were numerous significant rainfall events starting in late April through mid July.
Early season rains provided significant recharge (in the purple shaded oval) to deep water tables following the droughty 2021. You can see the responsiveness and depth between landscape positions with the lower position generally more responsive and having the shallowest depth.
The green shaded ovals show rapid decreases in water table depth, followed by tile drainage drawdown.
If took more time for the Upper position water table to get into that near surface zone, and we believe it is falling due to lateral, downslope movement.
For soil moisture, the chart in the upper right shows soil moisture in VMC % (left axis) at the 30-45 cm depth (yellow), 75-90 cm depth (blue) and 105-120 cm depth (black). Again, daily precipitation is in the grey bars.
Following thawing of soils around Apr 29-May 5, we can see soil moisture starting to respond to rainfall and infiltration. Soil moisture was decent at the start of the season owing to some fall 2021 rain. Of note, we can see the soil moisture slowly but steadily increasing at the 105-120 cm depth and this corresponds to the rise in the water table we saw in the previous slide.
At the Mid-Lower position, thaw occurred about a week later between May 5 to 11.
We can see a more rapid response following thaw, perhaps due to a combination of rainfall and lateral in-flow from up-slope.
And we can see soil moisture rising above FC into that saturation zone as the water table increases, then the effect of the tile allowing the soils to drain back down to FC.
At the Upper, undrained location you can see that deeper soil moisture is staying in that saturation zone from mid to late June to end of July.
So, what are we seeing for tile flow?
The chart here shows tile flow from Plot A between July 6 and 20. Flow is presented in both L/s and US gpm.
Flow from the Upper-Mid location is shown in blue, from the Lower-MID position in fuscia and the Lower position in gold.
You can see consistently higher flow rates in the lower position relative to the lower-mid then the upper-mid position. This is pretty intuitive and follows the story of water tables and soil moisture.
In terms of magnitude, during the late July flow event following 1.4 inches of rain on July 18 & 19 , the flow from the Lower-Mid position was 1.7 x greater than the Upper-Mid, then the flow at the Lower position was another 2.4 x greater.
Finally, let’s take a quick look at water quality. We are interested and are measuring nitrogen, phosphorus and electrical conductivity, but don’t have the nutrient results yet.
This chart shows electrical conductivity, as a measure of salinity, between July 6 and 20 at Plot A.
Again, flow for the Upper-Mid position is in blue, the Lower-Mid position in fusica and Lower position in gold. The grey dotted lines show flow at the Lower position simply for reference.
We can clearly see conductivity values are highest in the Lower position flow, and are generally higher at the Lower-Mid position relative to the Upper-Mid position. So, there is a landscape position driver in this component of water quality. Which makes sense in this case, as the lower slope position is more highly impacted by soil salinity.
We expect EC to decrease over time as salts in the soil are reduced.
So, as a brief summary of preliminary conclusions…
We are finding that soil moisture, water table, tile flow and water quality (EC) are all following an intuitive, soil landscape model.
These findings will HOPEFULLY have ramifications for conversations around BMPs such as design and layout decisions for performance optimization – whether economic, agronomic or environmental.
The following slide provides an overview of next steps.
Our current project funding is wrapping up in December of this year.
This will include completing DRAINMOD –S modelling to evaluate long-term trends in hydrology and salinity based on site conditions and early findings.
We now have funding in place to establish edge-of-field treatments including a constructed wetland, and a phosphorus removal structure at the site, and a saturated buffer at an alternate location.
We have a proposal submitted as well for a 5 year monitoring program which will allow us to continue evaluation and knowledge transfer.
With that, I would like to again thank IDS and you folks for the opportunity to provide some information on the project today.
If you have any questions I can answer them now, or you reach out to myself or Bruce Shewfelt at PBS Water Engineering.