Conservation management practices can increase sugar beet yields over time – that’s one of the key messages from a 12-year irrigated cropping study that compared conservation and conventional management.
Soybean production is spreading across the Prairies. In 2016, Manitoba had nearly 1.64 million acres seeded to the crop, and Saskatchewan seeded 240,000 acres. In Alberta, production is still relatively low at around 15,000 acres, according to industry estimates. But with early and very early maturing varieties becoming more common and with the expanding soybean crushing capacity in the province, more Alberta growers are considering this crop.

Now, two collaborating soybean projects with agronomic, economic and varietal studies are nearing completion. The results will help create a solid foundation for soybean as a profitable crop option on irrigated land in southern Alberta.

Manjula Bandara, a special crop research scientist with Alberta Agriculture and Forestry (AAF), is leading one of the projects, and Frank Larney, a research scientist with Agriculture and Agri-Food Canada (AAFC), is leading the other.
WTCM36 7 IMG 0830 AO
Photo courtesy of Andrew Olson.

Bandara has been working on soybeans since about 2004, when he started conducting variety trials in southern Alberta as part of the Western Soybean Adaptation Trials. Bandara’s group tested Roundup Ready and conventional varieties under both rain-fed and supplementary irrigation conditions. In the first few years of the trials, soybean yields ranged from about 267 to 3,703 kilograms per hectare (kg/ha). Over time, as breeders developed improved early maturing varieties, the yields in these trials rose to around 3,000 to 4,000 kg/ha (45 to 60 bushels per acre, or bu/ac).

Most Alberta soybean production is on irrigated land. In Bandara’s trials, some varieties gave reasonable yields under rain-fed conditions, but supplementary irrigation improved their yields. For instance, one variety yielded 3,185 kg/ha under rain-fed conditions and 3,646 kg/ha with supplementary irrigation. Other varieties and lines really responded to irrigation. For example, one line more than doubled its yield, going from 2,038 kg/ha when rain-fed to 4,581 kg/ha under supplementary irrigation.

“With these results, we were convinced that we could grow soybean under supplementary irrigation conditions in southern Alberta,” Bandara says. “Then I talked to several growers and Patrick Fabian [of Fabian Seed Farms in Tilley, Alta.], who has been conducting some soybean research himself, encouraged me to submit a research proposal on soybean.”

That led to Bandara’s current four-year research project on irrigated soybean production, which runs from 2014 to 2017. The project has four components. The first is evaluating new soybean varieties and lines. The second is assessing various production practices, such as seeding density, row spacing, root nodulation, and irrigation scheduling. The third is comparing the benefits of soybean versus dry bean production and the final one is testing the most promising agronomic treatments from the small-plot experiments under field-scale production.

Variety evaluations
The variety trials in Bandara’s current project are taking place under supplementary irrigation in Brooks, Medicine Hat, Bow Island and Lethbridge, Alta. Each year, his team is testing 16 to 18 Roundup Ready varieties and three conventional varieties. The seed companies participating in the trials select which of their latest varieties/lines they would like to include in the testing. The conventional varieties are all older varieties.

Bandara’s team is collecting data on such traits as pod clearance, yield, days to maturity, and heat units to identify which varieties/lines have the best traits for commercial production in southern Alberta.

Pod clearance refers to the height above the ground of the lowest pod on a plant. “Soybean plants produce their heaviest seed in their lowest pods. To be able to harvest those good, heavy seeds, the varieties need high pod clearance. I would say the lowest pod on the plant should be at least six centimetres above the ground,” he notes.

As well, the varieties must be high yielding. Bandara explains that if soybean is going to find a place within irrigated rotations in southern Alberta, it has to be at least as profitable as well-established irrigated crops like corn, dry bean and sugar beet. The project is targeting soybean varieties that yield more than 4,000 kg/ha (60 bu/ac) in the small-plot trials; under farm field production, the actual yields would be somewhat lower. A few of the varieties in the trials are meeting that target and Bandara has heard some irrigation farmers in southern Alberta are getting close to 60 bu/ac with certain varieties.

Early maturity is also essential. Soybean maturity can be described in various ways including: maturity group (a rating based mainly on day length, but also influenced by temperature); the number of crop heat units (CHU) needed to take the variety to maturity; and the number of frost-free days needed for maturity. Most of the soybeans in Bandara’s trials are in the 00 maturity group, which includes early- and mid-season varieties for the Prairies.

One of the interesting findings from this work is that not only are the total CHUs important, but when those CHUs occur is also key. “We broke down the heat unit requirement based on the crop’s phenological stages [growth stages]. We found that heat units received during flowering, pod set and post-flowering are critical for higher seed yields,” Bandara explains. “We have to determine when a variety is flowering and what heat units it will be receiving. So it is not just the variety itself, but how it matches with the local growing conditions.”

AAF plant pathologist Mike Harding is monitoring the varieties for disease, but very little has occurred in the trials.

Bandara’s results so far show that, when soybeans are seeded in the second or third week of May, the varieties that mature within 116 to 121 days under southern Alberta conditions will be the highest yielding, good quality varieties for the region.

Seeding density, row spacing
“Soybean is such a new crop for Alberta that little information is available on agronomic questions that new growers would be asking about,” Larney says. His project aims to find answers to some of those questions.

Larney is collaborating on the project with Bandara and Doon Pauly, an agronomy research scientist with AAF. Tram Thai, a master’s student at the University of Lethbridge, is also working on the project under the supervision of Larney and James Thomas with the university’s department of biological sciences.

One of the studies in Larney’s project took place at Bow Island and Lethbridge from 2014 to 2016. It compared two row spacings (17.5 and 35 centimetres) and three seeding densities (30, 50 and 80 seeds per square metre, or seeds/m2) for the Roundup Ready soybean varieties NSC Tilston and Co-op F045R. Bandara chose the soybean varieties, picking two that had done well in his variety trials.  

Larney’s team collected data on characteristics such as emergence, days to flowering, plant height at flowering, days to maturity, plant height at maturity, and pod clearance. They also measured yield components like pods per plant, seeds per plant, thousand seed weight, and seed yield, analyzed nitrogen uptake in the plants and estimated the amount of nitrogen returned to the soil from the aboveground crop residues.

Data analysis is partially completed; Larney highlights some of the initial results from the 2014 and 2015 growing seasons. “The main effect was with the seeding density. When we averaged the data for both sites and both years, we saw a yield increase as the seeding density increased. At 30 seeds/m2, yields were between 2,200 and 2,400 kg/ha. At 50, we had 2,600 kg/ha and at 80 seeds/m2, we had almost 3,000 kg/ha, do there is a difference of about 600 to 800 kg/ha in yield response from the lowest to the highest seeding density.”

He adds, “However, there is a trade-off between the yield from the extra seed and the cost of the extra seed.” The team is planning to do an economic analysis to find the economically optimum seeding density.

Higher seeding densities also resulted in taller soybean plants with higher pod clearance. “Averaged over the two years at both sites, at 30 seeds/m2, the lowest pod height is five centimetres; at 50 seeds/m2, it is six centimetres; and at 80 seeds/m2, it is seven centimetres.” As well, higher seeding densities were associated with slightly earlier maturity and higher nitrogen levels in the grain and straw. Soybean disease wasn’t an issue, even in the denser plantings.

The wider row spacing treatments had taller plants at flowering, better pod clearance, and slightly earlier maturity than the narrower treatments. Row spacing didn’t have a significant effect on yield.

The Bow Island site had slightly higher heat units and about 10 fewer days to maturity than the Lethbridge site. However, the yields at Lethbridge were just as good as those at Bow Island.

Soybean versus dry bean
Larney’s and Bandara’s projects each have a study comparing soybean and dry bean production. Larney’s study, which is taking place at Bow Island and Lethbridge, looks at the nitrogen benefits of the two crops.

“The current legume of choice under irrigation in Alberta is dry bean. The question is: would soybean acres be replacing dry bean acres? And, if so, what is the comparison between dry bean and soybean in terms of nitrogen carryover credits to the following crop in the rotation?” Larney says.

This study’s fieldwork started in 2014 and will be completed in 2017. He explains, “In year 1 [in 2014, 2015, 2016], we plant soybean, dry bean and barley. In year 2 [in 2015, 2016, 2017], we plant wheat in those plots. We apply six different nitrogen rates on the wheat and look at the yield response.” The wheat crop’s nitrogen uptake is used as a measure of the nitrogen credit from the previous soybean and dry bean crops, with barley as a non-legume check crop. In addition, the project team is collecting other nitrogen-related data such as the spring and fall soil nitrate-nitrogen levels and the nitrogen uptake by the different crops in year 1.

“I had always been told that, compared to other legumes, dry bean doesn’t fix that much nitrogen that is carried over to the subsequent crop, so I had thought soybean would be better than dry bean,” Larney notes. For example, Jeff Schoenau from the University of Saskatchewan has reported that, in Western Canada, soybeans fix 40 to 140 pounds of nitrogen per acre (45 to 155 kg/ha), while dry beans fix five to 70 pounds (six to 78 kg) and alfalfa fixes 100 to 250 pounds (112 to 280 kg).

Surprisingly, in Larney’s study, dry bean produced more nitrogen credits than soybean. “For example, in 2015, the nitrogen credits from dry bean were about two, to two and a half times greater than those from soybean. We had about 45 kg/ha of nitrogen from dry bean and about 20 kg/ha from soybean, averaged over Lethbridge and Bow Island. The results from 2016 also showed the nitrogen credits were higher for dry bean than soybean,” he says.

Larney’s team is planning to determine the nitrogen budgets for the different treatments to get a better handle on how much is being fixed and how much is being carried over.

Bandara’s study compares the profitability of soybean versus dry bean production. Once the field data collection is completed, Ron Gietz with AAF will do this economic analysis.

Irrigation scheduling
Another element of Bandara’s project is an irrigation scheduling study conducted at Brooks by Ted Harms, an AAF soil and water specialist. The study involved a Roundup Ready soybean variety and six different irrigation treatments: no irrigation (rain-fed); irrigation from flowering to pod set; irrigation from flowering to harvest; irrigation from pod set to harvest; irrigation from seeding to pod set; and fully irrigated, with irrigation from seeding to harvest.

The study developed a cost-effective irrigation schedule. Bandara says, “When we looked at how the different treatments affected yield, we found that early irrigation doesn’t have much impact. The most important period for irrigation is at flowering and after flowering. If you provide good moisture after flowering, then you can have yields of 3,300 kg/ha, compared to 3,500 kg/ha when fully irrigated.”

Field-scale trial and more
Bandara’s team is currently working with Fabian on a field-scale irrigation and seeding density study. On Fabian’s farm, they are testing the most promising treatments from the small-plot studies to see if any adjustments might be needed when using the practices on farms.

Once all the studies in Bandara’s and Larney’s projects are completed, the researchers will prepare a production manual for supplementary irrigated soybean. “At the end of the projects, we will be able to provide good insight into soybean production under supplementary irrigation in southern Alberta,” Bandara says.

Bandara’s project is primarily funded through Alberta’s Agriculture Funding Consortium; the contributing agencies include the Alberta Pulse Growers, Alberta Innovates Bio Solutions, Alberta Crop Industry Development Fund, and Country Commodities Ltd., a soybean meal processing company in Lethbridge. The main funders for Bandara’s variety evaluation work are the seed companies that provide the varieties for testing.

Funding for Larney’s project is from AAFC’s Pulse Science Cluster with matching funds provided by the Manitoba Pulse and Soybean Growers, and from Growing Forward 2.

Bandara is hoping to continue the soybean variety evaluation work after 2017, provided funding support from the seed companies is available. As well, he hopes to tackle some other soybean research topics. He notes that Alberta soybean growers are asking for research on white mould (Sclerotinia), which is likely to be a threat to soybean crops, especially under irrigation, and for research on rain-fed soybean production in the Dark Brown soil zone using newly available 000 very early maturing soybean varieties.
Variable rate irrigation (VRI) is a great idea, but many practical questions remain. Researchers are working to answer these questions so Prairie irrigation farmers and agricultural service providers will be able to more easily and effectively adopt VRI.
Droughts are a part of the Prairie climate and severe, prolonged droughts can put a strain on irrigation water supplies. Improvements can increase energy-use efficiencies, improve crop yields, and enhance the sustainability of water resources. Some of these improvements are also  eligible for current financial incentive programs.
It’s official: 2016 was the warmest year on record. The United States National Oceanic and Atmospheric Administration (NOAA) reports the average global surface temperature reached 14.83 C – the warmest it’s been since modern temperature records began in 1880.
A collaborative effort between Potato Growers of Alberta and the Oldman Watershed Council has produced three videos on watershed management and health. Click here to view the first of the three videos, highlighting the production history of the area.
Fertigation is quite common in southern Alberta, but very, very little research has been done on it in replicated plots,” says Doon Pauly, an agronomy research scientist with Alberta Agriculture and Forestry. His recently completed study took up the challenge of assessing the effectiveness of fertigation in wheat and canola.
So far, Alberta remains free of invasive mussels. Originally from Europe, zebra mussels and quagga mussels arrived in the Great Lakes in the 1980s. Since then, these two species have been spreading through North America’s waterways, clogging water-related infrastructure, damaging aquatic ecosystems and degrading recreational areas. In 2013, the mussels were found in Lake Winnipeg. In November 2016, they were discovered in a Montana reservoir.
Lodging can be a serious problem, especially in irrigated crops. Of course, variety selection and nutrient management are important tools for managing lodging. But producers may want to grow a crop variety with not-so-good standability because it has other important traits, and they may want to use higher nitrogen rates to capture a crop’s full yield potential, so four Alberta studies have investigated plant growth regulators (PGRs) as another tool for reducing the risk of lodging.
To replant, or not to replant is often the question when a sugar beet stand has been severely damaged. Ultimately, a grower has to do one or the other, and making the right choice will increase net returns from the crop. A six-year study has evaluated replanting recommendations for southern Alberta in light of the switch from conventional to Roundup Ready sugar beets. As a result, growers now have updated recommendations backed by solid data.
Variable rate irrigation is a challenging new topic for both producers and researchers, so we’re excited to be working on it and seeing what we can learn and share with producers,” says Alison Nelson, an agronomist with Agriculture and Agri-Food Canada (AAFC) in Manitoba. She is leading a three-year project, which began in 2015, to look into some of the key questions around variable rate irrigation (VRI) in potato production.
Saskatchewan’s growing conditions aren’t exactly ideal for corn, a crop that loves heat and water. But with the development of shorter-season hybrids, an increasing number of Saskatchewan growers are trying corn for silage, grazing or even grain. Irrigation can play a key part in making corn production more successful.

What are the key environmental parameters that impact pea yield? On the surface, the easy answer is temperature and moisture. Get them right and you get a top-yielding crop.

But what is the right combination? That’s what Rosalind Bueckert, a professor in the plant sciences department at the University of Saskatchewan (U of S) wanted to find out in an effort to better understand pea growth habits and to help improve pea breeding at the U of S Crop Development Centre (CDC).

“Pea cultivars are heat-sensitive so our goal was to investigate how weather impacted growth and yield for a dryland and an irrigated location,” explains Bueckert, who published the research in the Canadian Journal of Plant Science in 2015. “We explored relationships between days to maturity, days spent in reproductive growth – flowering to maturity – yield and various weather factors.”

Research in other countries had identified that high yield was related to early flowering, a large number of reproductive nodes and soil moisture availability during flowering. The longer the plant remained in the reproductive growth period, the higher the yield. Research had found that high daily maximum temperatures (31 C to > 34 C) during flowering for at least two to four days reduced yield due to abortion of buds and flowers, aborted young seed and potentially smaller seed. In Canada, though, the relationship between daily high temperatures, precipitation, and yield had not been explored.

Bueckert, along with colleagues Stacey Wagenhoffer and Tom Warkentin at CDC and Garry Hnatowich at Saskatchewan Irrigation Diversification Centre, Agriculture and Agri-Food Canada at Outlook, Sask., utilized the nine years of Co-op variety registration trials at the dryland Saskatoon site and the irrigated Outlook site to look at environmental effects on yield. They measured days to flowering when 50 per cent of the plants in a plot had an open flower, days to maturity, disease rating and seed size. The nine years covered the range of weather patterns with some hot and dry, warm, or cool and wet.

Check varieties in each year were utilized and represented current popular varieties. For example, in 2009 the five varieties were Eclipse, Cutlass, CDC Striker, CDC Cooper and CDC Golden. Peas were grown using recommended production practices. At Saskatoon, pea was not sprayed with a fungicide except in 2005 and 2009 when disease pressure was observed. At Outlook, pea was sprayed every year with a fungicide at flowering followed by a
second application 10 to 14 days later.


Critical maximum daily temperature
Bueckert says the length of reproductive growth was an important factor in yield, and that heat stress or lack of moisture caused flower and reproductive node abortion. Conversely, the longer the pea spent in the reproductive growth phase, the higher the yield.

“Pea was sensitive to heat but heat units did not satisfactorily describe growth and yield in all environments,” reports Bueckert. “Strong relationships were observed between crop growth and mean maximum daily temperature experienced during reproductive growth, and between crop growth and mean minimum temperature.”

The researchers found that when the mean maximum temperature was greater than 25.5 C at the dryland site, the number of days in reproductive growth was reduced to less than 35 days. More than 20 days above 28 C meant less time in the reproductive phase and lower yield for dryland pea.

“The threshold maximum temperature for yield reduction in the field was closer to 28 C than 32 C from [other] published studies, and above the 17.5 C mean seasonal daily temperature,” Bueckert explains.

At Outlook, irrigation helped to buffer the effect of heat, and the pea remained in reproductive growth for 35 to 40 days in a wider temperature range of 24.5 C to 27 C.

To put those temperatures into perspective, average climate data shows that from June to August, Saskatoon experiences 11.5 days above 30 C and Outlook 12.3 days.

“Clearly, mean daily maximum temperatures exceeding 25 C were associated with shortened reproductive phases of less than 35 days at both Saskatoon and Outlook,” Bueckert says.

Plant breeding implications
On the Prairies, late-maturing varieties take about 94 days to mature, with medium maturity varieties around 90 days and the earliest at 86 days. Yet the normal frost-free period for Outlook is 123 days and 117 days for Saskatoon. Bueckert says plant breeders could lengthen maturity in pea by at least seven days without frost risk. If plant breeders could get the pea to flower earlier and longer (more indeterminate growth), yield potential could be increased.


Nov. 2, 2015, Ontario – Climate change is making Ontario’s farmers look carefully at water conservation and efficient use.

Agriculture is a significant water user in the province, and after experiencing drought-like growing conditions in 2012 and watching regions in the United States deal with severe water restrictions, Ontario agricultural researchers are working to find new cropping methods to use water as efficiently as possible.

In Ontario, crop irrigation systems are most commonly used on fruit and vegetable crops; fewer than 5,000 acres of field corn are currently irrigated.

However, irrigation is essential to producing maximum corn yields in parts of Ontario, leading researchers and irrigation experts to team up to find new ways to irrigate crops in a more water conscious and efficient manner.

The result is a new-to-Ontario below ground crop watering system, Subsurface Drip Irrigation (SDI).

Since 2013, University of Guelph Plant Agriculture professor Rene Van Acker has led a research team studying this low-pressure, high-efficiency irrigation method that uses buried polyethylene drip lines to bring water and nutrients to crops.

The team has been testing the system in corn fields, since corn requires more inputs like water and nutrients than other Ontario-grown field crops.

“Traditional crop irrigation methods are very labour intensive with inefficient water and energy use,” says John O’Sullivan, also a professor in the University of Guelph’s Plant Agriculture department and the on-site project manager of the SDI research.

O’Sullivan explains customary irrigation systems use aluminum pipes laid above ground and across fields, using overhead water sprinklers to deliver water to crops.

Mobile sprinklers are also popular, but use a lot of energy and of the irrigation water applied, as little as 50 per cent is actually used by the crop.

“SDI can deliver water with an efficiency of 95 per cent or higher and keep corn root zones closer to optimum soil moisture and maximize fertilizer utilization,” says O’Sullivan.

The team has proven SDI is the most efficient system with water savings of 25-50 per cent when compared to traditional overhead water irrigation.


Burying the SDI water lines instead of sprinkling water onto the crops immediately boosts water use efficiency by eliminating water evaporation from above ground sun and air exposure.

Unlike other drip irrigation systems where water lines lay flat on the ground surface, SDI drip tapes are buried 14” in the ground.

Doubling the efficiency of the new irrigation system, crop nutrients, or fertilizer, can also be added to the water pumping through the sub surface irrigation lines.

This allows farmers to deliver exact amounts of fertilizer to the crop throughout its growing stages. And since nutrients are applied right at the plant’s root level, very little is left unused, which reduces the chance of fertilizers leaching into the environment.


“It’s like spoon feeding our plants,” says Gary Csoff, technology development representative with Monsanto Canada Inc., who points out the ability to apply nutrients through the SDI system also maximizes the crop’s yield, quality and the farmer’s economic investment in costly crop nutrients.

“This new crop production technology will maximize productivity per acre while protecting our environment,” says O’Sullivan, adding that a one per cent adoption rate of SDI by Ontario farmers would generate an additional $10 million in farm gate sales through increased yields and more efficient nutrient management.

SDI research has been funded by Farm and Food Care Ontario’s Water Adaptation Management and Quality Initiative.

The research team has also been awarded funding through the University of Guelph’s Gryphon’s LAAIR (Leading to Accelerated Adoption of Innovative Research) program to continue testing and conducting demonstrations to farmers interested in adopting this new technology. The Gryphon’s LAAIR is supported through Growing Forward 2, a federal-provincial-territorial initiative.

“This is an out of the box approach to irrigation that has stimulated a lot of thought and discussion,” says Csoff.

The SDI research team also received input support from Peter White, Irrigation Research Associate at Simcoe Research Station, Todd Boughner of Judge Farms in Simcoe, and Vanden Bussche Irrigation of Delhi.



Dry conditions can significantly reduce soybean yields, so a five-year project is underway in Ottawa to add drought tolerance into Canadian soybean varieties.

“Drought stress is the major abiotic constraint to high stable soybean yields in Eastern Canada. From 2000 to 2012, Ontario had five summers that were drier than the long-term average. That is one year in three with drought,” notes Malcolm Morrison, the project’s principal investigator. He is a plant physiologist at the Eastern Cereal and Oilseed Research Centre (ECORC) of Agriculture and Agri-Food Canada (AAFC).

Morrison explains the project isn’t about prolonged periods of extreme drought like the Dirty ’30s. Instead it’s about short periods of dry weather within a growing season. “This is called ‘periodic drought,’ and it can be quite dangerous for soybean yield, especially if the dry weather occurs during sensitive growth stages,” he says.

“We’ve found that the first three or four weeks after the beginning of first flower is about the most sensitive stage to changes in precipitation. If you get precipitation at that time, you will be rewarded with a higher yield. But if you get drought, you will get fewer flowers producing pods and fewer seeds in those pods, and that will affect yield.”

Along with yield reductions, dry conditions can also influence seed quality. As rainfall decreases, protein content decreases and oil concentration generally increases slightly. In addition, the seeds tend to be smaller and may be misshapen or wrinkled.

Morrison points out the ability to tolerate periodic drought is particularly important for reliable soybean production in Canada. With our relatively short growing season, a soybean plant will have little time later in the season to compensate for a reduction in seeds that has occurred due to dry weather.

Screening for multiple mechanisms
The project, which runs from 2013 to 2018, is screening non-GMO soybean lines from AAFC and Sevita International for drought tolerance. The selected lines go to the breeders for development of new and improved Canadian soybean varieties.

Many characteristics can influence how well a soybean plant does under dry conditions; some examples include a deeper root providing access to deeper soil moisture, or early vigour so the plant shades the soil surface sooner, or more efficient water use, or earlier closure of leaf pores, called stomata, to stop water loss from the plant.

“There are lots of different drought-tolerance mechanisms that can be brought into play in a plant, but those mechanisms can be detrimental to yield in a year with a lot of moisture,” Morrison explains.

He gives the example of earlier stomata closure. When the stomata are open, they allow water vapour and oxygen to escape from the leaf, and carbon dioxide to enter. So, earlier stomata closure does more than stop water loss. “If a plant closed the stomata early, then it wouldn’t have enough carbon dioxide for photosynthesis even when the drought conditions aren’t that bad. If we bred a plant like that, it would be really good in dry conditions, but not in wet conditions.”

One key drought-response issue for soybeans is that dry conditions can halt nitrogen fixation. Morrison says, “Nitrogen fixation is a symbiotic relationship between a bacterium and the plant that produces the root nodule. The bacteria that live in the nodules receive carbon from the plant and in return supply the plant with nitrogen. But as the plant responds to a dry condition, the stomata close and it stops actively photosynthesizing, it stops producing carbon, and it stops moving that carbon down to the nodules and giving the bacteria food.”

Given the complexity of drought-response traits, Morrison isn’t screening for just one or two specific traits. Instead, he is using a method that identifies the plants that “can capitalize on several drought-tolerance mechanisms to produce high yields under dry conditions and high-moisture conditions.”

For this method, Morrison supplies field-grown soybean plants with water every day and then compares the yields of those irrigated plants to the yields of the same soybean lines grown in adjacent plots that have received only natural rainfall. “This is called the Delta Yield concept because it is based on the difference between the yields of the well-watered plants and the yields of the natural-watered ones.” “Delta” refers to the Greek letter delta, an abbreviation used in science for “the difference between.”

The researchers want to find soybean lines with very little yield difference between the irrigated and rain-fed plants. “The cultivar with the lowest Delta Yield is the most drought-tolerant, yet won’t suffer a yield drag when there is no drought,” Morrison explains. “This method has been used in the United States to develop a water-use-efficient corn hybrid that yields 7.4 per cent higher in drought and 3.4 per cent higher in normal water situations.”

For the irrigated plots, Morrison uses a product called Drip Tape made by Toro. “It is a plastic tape that is buried at five inches deep. Every 30 centimetres, there is a small slit in the tape, and that leaks at a certain amount when you put water into it. On a daily basis, I give the plants between two and three millimetres extra precipitation.”

This subsurface irrigation method has a lot of advantages. Morrison says, “It saves on water; we don’t have to apply a huge amount of water to the surface. It also allows us access to the field to take measurements because the soil isn’t mucky. And it allows a fairly precise application of water; we know how much we’re putting on per area.”

From previous research, Morrison knows soybean plants respond well to extra moisture, as long as it doesn’t come all at once and flood the plants. “We’ve done experiments showing that you can get an increase in yield with up to 650 to 700 millimetres of precipitation during a growing season, if the precipitation is evenly distributed.” That amount of rainfall is quite a bit higher than the average growing season rainfall in Ontario’s soybean growing areas. For example, Ottawa’s 30-year average growing season precipitation is 466 mm.

According to Morrison, the Delta Yield approach works very well in most years, although the differences between the irrigated and non-irrigated yields are not as noticeable when precipitation is abundant, as it was in 2014 in the Ottawa region. But he adds, “Even in 2014, we still had periodic drought in the first two weeks of August. That is always going to occur, and that is why we are doing the research – we’re aiming for a plant that has the capacity to kick-start mechanisms that get it through those rough points in the growing season.”

Even though drought-tolerance traits can be doubled-edged in wet years, some drought tolerance is almost always better than none, as shown in research led by Thomas Sinclair of the University of Florida. The researchers modelled the response of soybeans with different drought-tolerance traits using 50 years of weather data for 2655 U.S. locations. “They found that, in the vast majority of times, incorporating any drought-tolerance mechanism is actually beneficial because at some point in time during the growing season you are going to have a periodic drought, even in years of abundant moisture,” Morrison says.

When he first started experimenting with the Delta Yield approach, he tested it on some old soybean varieties. “One of those was Maple Arrow, released in 1976. Maple Arrow is a watershed variety because it was the first short-season variety. It is the progenitor of all the short-season soybean varieties in Canada. Interestingly, we found that Maple Arrow had quite a low Delta Yield in a dry year, so it is inherent in its capabilities for drought tolerance.”

Morrison is making good progress in the current project. “Every year, we test 20 Sevita experimental lines and 12 Ag Canada experimental lines to try to find drought tolerance. We have found some lines that have great performance under irrigation but not very good performance under normal conditions. And we’ve found some with very low Delta Yields, which is what we’re looking for.”

He notes, “In the first year of the project, we tested a lot of foreign soybean material, lots of Chinese lines and a couple of Indian lines.” However, most of the drought-tolerance genetics they are testing originally came from U.S. soybean breeding programs, which have identified lines with various strategies for dealing with dry conditions. The breeding programs at ECORC and Sevita have been and are breeding those genetics into Canadian-adapted backgrounds for testing by Morrison. For example, Elroy Cober, the soybean breeder at ECORC, is currently incorporating genes for drought-tolerant nitrogen fixation, and Morrison will be screening those lines in the future.

Overall, this project aims to contribute to the development of Canadian soybean cultivars that have greater yield stability across all years – whether the conditions are dry, normal or wet. “This will result in greater average yields and higher profits for Canadian soybean growers,” Morrison says.

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