WESTERN PRODUCER — Tile drainage may be the best tool in the toolbox to manage saline soil in fields, a southwestern Manitoba farmer told an audience at Ag Days in Brandon, Man.
Aaron Hargreaves, who co-owns Harwest Farms south of Brandon, said he and his four partners have struggled with soil salinity on their farm since they established it in 2013. They’ve taken a number of measures to address the issue, but none have proven as effective as tile drainage.
“It’s the best tool in the toolbox that we have found,” Hargreaves said during a discussion of the impact tile drainage can have on soil salinity.
“Results can vary. Compaction, soil type and rainfall can all have an impact. But nothing else works the same as tile.”
Hargreaves and his partners started experimenting with tile drainage soon after starting their 17,000-acre farm, after they heard U.S. producers talk about its effectiveness and the improvements in corn and soybean yields as well as salinity.
Hargreaves said tile drainage has had a positive impact on many problem fields. Yields have increased dramatically in many of those fields and the reduced saline has allowed the partners to plant crops that would have fared poorly in the past.
“Pinto beans are extremely sensitive to salinity, but they are growing well in that area of the farm now. We couldn’t even grow canola in the field four or five years ago.”
Tile drainage reduces excess water in the crop rooting zone by lowering the water table. This allows a plant to put roots deeper into the soil to better access nutrients. Tile drainage only removes water that is above a field’s capacity.
A tile drainage system has three components: lateral lines of perforated pipe that collect excess water from a field; mains or headers that deliver that water below ground; and a gravity- or mechanically-operated outlet that pumps the water into a ditch or other collection area.
Hargreaves said producers considering tile drainage should be aware of the cost. Basic installation typically ranges between $1,000 and $2,000 per acre. There can be additional costs, such as a lift station, which is used to move subsurface water from a lower to higher elevation when natural gravity flow isn’t sufficient to handle the job.
Lift stations are expensive, Hargreaves said, and most require an electrical source to operate.
“They increase the cost of the project a lot and sometimes that makes it not worth doing,” he said.
Hargreaves and his partners installed a solar-powered lift station on their farm for the first time last year, but he said the jury is still out on its effectiveness, since it will only operate for as long as the sun is shining.
Producers should also be aware lift stations need to be regularly monitored and serviced. There are several companies that sell electronic monitors that can send alerts to a mobile device indicating whether the pump is working.
There are two types of tiling systems: pattern and selective.
Pattern tiling refers to cases where every acre of a field is tiled. Selective tiling involves only certain areas of a field.
Hargreaves said each has its pros and cons. Pattern tiling allows a field to be seeded earlier, leads to more uniform crop maturity, and machinery is less likely to get stuck on hilltops.
The downside is that it can be expensive to install. The cost of selective tiling can be more expensive per acre due to higher installation costs, but the overall cost per field is generally lower and it can provide a faster return on investment.
“Most years, (selective tiling) is adequate in fields with good natural drainage,” he added.
Hargreaves said he and his partners found that in cases where selective tiling was installed, narrower spacing of the perforated pipe is more effective. In most cases they have spaced the pipes 25 feet apart rather than the standard 50 feet.
He suggested it can sometimes be better to err on the side of caution when installing tile drainage. Even though a saline problem area may be quite narrow, he recommended that tiling be extended well past the outer edge.
An unexpected benefit of tiling has been the “huge” impact on weed control, especially kochia, he said.
“Roundup-resistant kochia is prevalent in our area. In a tiled area in our field we are reducing the amount of kochia in that field by 75 to 90 per cent easy. It’s a hugely effective tool in the management of kochia.”
David Whetter, a soil scientist and president of AgriEarth Consulting, said during an Ag Days seminar that farmers will need to do their homework before deciding to use tile drainage.
“It’s a big investment and producers know their land the best. My advice is to make sure that you’re part of the design process in terms of that kind of gut feel. Does the design make sense? Are the right areas being drained? Seek advice where there’s any uncertainty just to make sure you can optimize your investment.”
Whetter said one of the most important factors to consider is drainage coefficient — that is, the number that describes the maximum rate of water removal for which a tile is designed.
For example, a drainage coefficient of a quarter-inch of excess water in a day is the typical design standard. That means, in the case of a one-inch excess rainfall event, it will take four days on average to remove that excess water from a field. The higher the drainage coefficient, the higher the cost of the drainage system.
Another design consideration is depth of tile or pipe. A minimum depth of 2.5 feet is typically required to maintain pipe integrity. In Manitoba, the typical depth of installation is between three and four feet.
It’s also important to consider any restrictive layers in the soil, Whetter said. This can include areas where sand is located on top of clay, or where there is significant compaction that can make installation more difficult and affect tile performance.
In parts of the Prairies, farmers sometimes have to contend with excess water and drought in the same growing season. That’s why getting the water table at just the right height is so important with a tile system, he added.
“The golden rule is to drain just enough water for crop growth but not a drop more.”
Also complicating decision-making are the Prairies’ variable soil landscapes.
“The takeaway here is the snowflake analogy. Every field is unique, and it really requires a field-specific solution, particularly when we get into these variable landscapes,” Whetter said.
Tile drainage has often been linked to increased productivity. Studies from Iowa, Ohio and Ontario have shown increases in yield for corn and soybeans grown in fields with subsurface drainage of between four and 45 per cent.
A recent study run in Minnesota showed yield increases of 10 to 30 bushels per acre for corn and four to 15 bushels per acre for soybeans.
“A sad story is that we don’t have a lot of good local data, at least not that’s out in that public realm. We have to lean on other regions to look at data, and even then, there’s not a lot of data out there. Manitoba or Prairie region results are really needed here.”
That’s partly why Whetter and a colleague helped develop the Souris Plains Soil and Water Management research site. It’s a 320-acre field-scale research demonstration site, with just over half hooked to tile drainage systems.
It monitors tile flow, water quality, water table depth and soil moisture above and below tile in a variety of different landscape zones. Preliminary results from the site, which was launched in 2020, showed a “pretty clear” indication in soil salinity reduction after just one year of tile drainage, although Whetter stressed that further study is required.
Hargreaves offered one final piece of advice to producers: be patient.
“It can take time (to have an impact). In an area like Nesbitt (about 30 km south of Brandon) we’ll see results lots of times in one or two years to fix the spots where the salinity isn’t too strong. Where it’s really bad, it’s still going to take a long time.”
