Prairie pothole consolidation has been occurring almost from the time the first farmers arrived. The concept is simple. Drain small nuisance wetlands into one large pothole to gain arable acres.
Fast forward to 2020 and we see serious concerns about the impact on salinity, water tables, downstream nutrient load and actual productivity of those rehabilitated acres? Those are questions being probed at the Glacier FarmMedia Discovery Farm at Langham, Sask.
The two-year study will assess productivity on drained soils while limiting off-site nutrient loss in runoff water on the 40 acre project site.
This fall, Jeff Penner from Swan River, Man., employed his V-Wing to consolidate minor potholes that experience occasional flooding. Some were channelled into a larger pond, while other small wetlands were channelled through an outlet into the North Saskatchewan River.
Blake Weiseth, the lead researcher at Discovery Farm, said the Saskatchewan Water Security Agency (WSA) was involved from the beginning and was in charge of the overall design and engineering on the project.
“Jeff took their blueprint and added some of his own experience to make the drains meander around the field so we have no deep water channels,” said Weiseth, adding the shallow snake-like drains should reduce water erosion and will be easy to seed through.
A post-construction survey by WSA ensured runoff water will be effectively moved and contained within the landscape, according to the plan.
“The RTK topography determined the Discovery Farm has a total of eight mini-watersheds in the project area. Some are flooded the whole year. Others are just too wet to seed or you can seed through them a little later. We have the whole range of classes here. The total project area is about 40 acres.”
On the west side of the project, three small wetlands are being consolidated into one large permanent pothole about an acre in size. On the east side of the project, the remaining five basins were connected and then channelled toward the North Saskatchewan River. The water table is up near the surface in certain areas, which can make construction difficult.
Construction and subsequent research are funded by the WSA along with the Saskatchewan Soil Conservation Association and the Saskatchewan Stock Growers Association.
Weiseth said a major research component is to explore the agricultural potential of drained wetlands with an emphasis on improving nutrient uptake, thus reducing the nutrient load down-stream. This will include fertility management, residue management and novel cropping practices. The greater nutrient mineralization on the drained soil should allow Weiseth to grow crops with a reduced fertility prescription.
The residue management treatment will focus on shallow incorporation of trash into the soil to reduce contact between residue and snow runoff water. This should reduce the amount of soluble phosphorous flowing away in runoff.
The novel cropping treatment will look at the use of mixes of annual forages, including legumes. The reduced fertility requirement at seeding with legumes should reduce nutrient losses in the runoff water.
A separate five-year project at Discovery Farm in partnership with Ducks Unlimited Canada and Proven Seed will compare the ability of perennial forages to establish on saline soil and will see whether these species have the ability to influence surface soil properties such as salinity and organic matter.
“If we want to remove salt from the test area, then we have to bale the forages and remove the bales for cattle feed. The hope is that actively growing forages will help prevent the water table from rising to the surface, bringing dissolved salts with it.”
Another objective is to look at the impact on water quality of various agricultural management practices on drained soils. What kind of special management practices might be required to get the most out of drained soils, while still protecting water.
“Here’s what we want to explore. As a farmer with drained wetlands, what can you do to be a good steward of that soil and water?
“We’re hoping to demonstrate how an effective water management plan can use surface drainage and farming practices to improve productivity of flooded soils and limit nutrient losses. At the same time, we’re preserving the ecology in a permanent wetland where water is being collected. Crop establishment on these drained areas should also prevent the problem of salinity from worsening.”