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Each farm must weigh the pros and cons of straw management options as it relates to their cropping system and long-term goals. Once all relevant factors are assessed, the best management practices for that farm can be implemented.

Crop Residue Production

For cereal crops, about 1.66 lbs of straw is produced for every pound of grain harvested. However, this value can vary from 1lb to 4lbs¹. Quantities of straw produced in wheat or barley crops will vary based on the crop, variety, soil zone, soil and environmental conditions, and yield of that crop.

Depending on farm goals, agroecological zone, and available markets, the management of straw may differ. Although chaff can provide value to certain production systems³, this document will focus on straw management.

Nutrient Content in Straw

Straw contains nutrients that should be accounted for when making residue management decisions⁴. Table 1: shows the average nutrient contents for wheat, barley and oat straw not including chaff.

Farmers should assess the nutrient content of the straw and then determine the fertilizer equivalent value. If the straw is being removed and sold, this information is valuable for two reasons: i) Determines the fertilizer equivalent value of the nutrients being removed and sold compared to the price received for the straw. However, baling, and physical removal will need to be considered in pricing as well. ii) It provides the value of nutrients being removed from their field in the form of straw so field nutrient balance can be maintained.

¹ Approximate values of various fertilizer sources in the summer of 2022

To assess the nutrient value straw, multiply the amount of nutrient per tonne of straw (Table 1) by the value of each pound of nutrient within the desired fertilizer source (Table 2). From this, a value per tonne of straw can be determined (Table 3). Alternatively, farmers can use the Manitoba Agriculture Straw Cost Calculator,which takes into consideration the value of nutrients.

The actual nutrient value content in straw will vary depending on many factors. Farmers who wish to assess actual straw nutrient values are recommended to collect representative samples and submit for analysis at a soil testing lab.

¹ Approximate values of various fertilizer sources in the summer of 2022 Source: Alberta Agriculture and Forestry (Straw Manufacturing in Alberta. 2020. Alberta Agriculture, forestry, and rural Economics⁵)

The Release of Straw-bound Nutrients Over Time

When calculating the nutrient content of straw, one may be inclined to contribute the straw nutrient content to next season’s fertilizer plan. However, straw-bound nutrients are released back into the soil over multiple years due to the length of time it takes for the straw to break down. Instead, farmers should consider the nutrients tied up in straw as a long-term investment that, if maintained on the field, will mitigate the decrease of soil nutrients over time.

Breakdown and release of straw-bound nutrients will vary depending on several factors including moisture, temperature, soil biology, carbon to nitrogen ratio, size of the straw particles, amounts added and other soil characteristics.

Cereal straw has a high C:N ratio. Therefore, breakdown of straw will initially require the use of plant available nitrogen from the soil. A portion of the soil nitrogen will become unavailable to the following year’s crop for a portion of the season to assist with straw breakdown. After the straw is broken down, that nitrogen will once again be available for crop growth.

Each nutrient may carry a different on-farm value depending on soil characteristics and nutrient levels

Although straw holds fiscal value in the nutrients that it holds, the on-farm value of those nutrients may vary depending on the current nutrient status of the farm it is being removed from. For example, Table 1 demonstrates the high potassium levels in straw. If a farm has low soil potassium, the value of the potassium in straw may hold equal or greater value than the value of potassium in synthetic fertilizer form. A decrease of soil potassium from repetitive yearly straw removal may decrease the field yield potential if removal of the straw lowers soil potassium to marginal levels. Conversely, a farmer with excess soil potassium may not contribute as much value to the potassium in straw. Farmers and agronomists must assess the value of each nutrient within the straw in relation to their farm and farm goals to understand the straw’s farm value. Working with an experienced agronomist is recommended when assessing the farm value of straw.

Organic Matter Value in Straw

In addition to nutrient value, straw holds value in organic matter potential. As straw breaks down in the soil through microbial processes, straw material will eventually become a stable organic matter.

Value of organic matter to crop production

Organic matter is a critical component of soil health. It influences nearly all soil properties and plays an important role in crop production.

• Soil moisture: Soil organic matter can play a role in buffering soil from moisture extremes. Increased organic matter can improve water infiltration under excess moisture conditions, and improve water holding capacity under drought conditions.
• Soil structure and mitigation of compaction and erosion: Stable soil aggregates (soil particles that are bound together) promote good structure and are an indicator of healthy soil. Their formation is encouraged by the presence of organic matter. A well-aggregated soil promotes water and air entry and can better resist erosion and compaction.
• Nutrients: Not only does soil organic matter contain important nutrients such as nitrogen, phosphorus and sulfur that become available as the organic matter decomposes, but it also can hold other important nutrients such as potassium, magnesium and calcium.
• Breakdown of herbicides: Soils with low organic matter can have an increased risk of herbicide carryover, particularly under dry conditions. Organic matter provides sites for herbicides to bind to, preventing them from impacting sensitive crops. In addition, soils with high organic matter often have increased microbial activity, speeding up herbicide breakdown.

Methods to Manage Excess Straw and Residue

The most effective straw management system utilizes multiple tools in a system. Through use of a systemsbased approach, straw volume can potentially be reduced. Below are options that farmers might consider to manage excess straw.

Prior to dropping straw

Variety selection

Crop type as well as variety selection impact the amount of crop residue produced. Semi-dwarf varieties are available and will help reduce the amount of residue. Reference your provincial seed guide and contact your local seed grower to discuss options that are available to you.

Alberta Seed Guide: https://www.seed.ab.ca/variety-data/cereals/

Saskatchewan Seed Guide: https://saskseed.ca/seed-guides/

Manitoba Seed Guide: https://www.seedmb.ca/pdf-editions-andseparate-section-pdfs/

Rotation

Although each crop type has specific residue challenges⁶, a good rotation will help mitigate the buildup of residue over multiple years. In general, cereal crops produce a larger quantity of straw compared to canola and peas. Sowing cereals multiple years in a row may lead to an excessive build-up of straw. Therefore, alternating between cereals and broadleaves will allow enough time between cereals crops for the cereal straw to break down and decompose.

Plant growth regulators

There are currently three plant growth regulators (PGRs)available to wheat and barley farmers in W esternCanada: ethephon (Ethrel), chlormequat chloride (Manipulator), and trinexapac-ethyl (Moddus). PGRs are synthetic compounds that can be applied to wheat or barley to target reducing lodging by shortening the plant stems. The stem shortening effect that PGRs can provide may be a useful tool for farmers to reduce issues with excess straw.

It is important to note that PGR response is highly variable depending on variety, environment, and year⁷. Additionally, due to the nature of PGR’s effect on plant growth, it is recommended that farmers have a clear understanding of the potential benefits and negatives of PGR use. For more information on PGR use in wheat and barley read: Plant Growth Regulators: What Agronomists Need to Know.

Straw choppers

Choppers help cut straw into smaller pieces at harvest while creating a more even straw distribution behind the combine. Straw management at harvest can reduce reliance on practices such as tillage or multiple harrow passes to manage straw. There are several factory and aftermarket options that can be matched to the combine header size for more even residue distribution. It is important to work with the manufacturer and dealer to fine-tune chopper settings for what is best for your operation.

Regular maintenance of all chopper components is crucial, especially after a heavy crop. Issues including dull knives, worn flails, or bent shafts can impact straw chopping.

A study funded by Sask Wheat and Sask Canola and conducted by PAMI completed in the fall of 2020 looked at original equipment and aftermarket choppers for residue distribution. The data from three sites showed that aftermarket choppers had several benefits including a more even residue distribution. The aftermarket choppers created more smaller fractioned residue of less than 0.5 inches compared to particles longer than 3 inches. The original choppers also left most of the residue directly behind the chopper⁸.

You can find more information about this project here: Performance Story: Effect of Cereal Crop Residue Distribution on the Following Year’s Canola Emergence and Yield — Sask Wheat Development Commission

After straw is on the ground

Bailing

Tillage

The value and disadvantages of tillage can vary greatly depending on agroecological zone. Below are a few points to take into consideration.

Harrowing

Harrowing is a common practice used to help redistribute straw and aid in residue breakdown. It can be done in the spring or the fall. It is better to harrow in the fall before the straw has a chance to settle and begin to break down.⁹

Harrowing redistributes the straw more than it incorporates. According to Manitoba Agriculture, there is only 5% of straw buried per pass with heavy harrows as compared to 40-60% with a tandem disc.¹⁰ Harrowing does not spread chaff as that must occur at harvest by the combine.

Swath Grazing

Swath grazing, the practice of windrowing straw and grazing cattle to feed is a management practice that can provide benefits to farmers with excess straw.

For more information on swath grazing, see Swath Grazing in Western Canada: an Introduction

Burning straw

In some conditions, such as in the presence of high moisture and on heavy clay soils, straw can be difficult to manage. In cases such as these, burning straw residue may be a management practice that farmers use. If burning straw, always consider the following:

• Be aware of local regulations: In Manitoba, farmers must follow the Controlled Crop Residue Burning Program, which restricts burning between August 1 and November 15 based on daily burn authorizations and requires burning permits in municipalities near the city of Winnipeg. Similar guidelines may exist in other areas.
• Supervise fire at all times
• Use fireguards: To prevent fires from spreading, till a fireguard around the field.
• Do not burn crop residue at night: Due to temperature inversions that often occur at night, smoke lingers near the ground rather than dispersing.
• Consider wind direction and speed: Ensure smoke will not travel towards roads, towns or neighboring residents. When winds are light, ignite swaths at 30-to-40-foot intervals. When wind speeds are moderate,burn against the wind to prevent fire from spreading.

Summary Benefits and Risks Summary

In summary, both removal and retention of excess straw will come with long- and short-term benefits or challenges. Additionally, each management option will have farm-specific benefits and challenges that each farm must assess concerning specific farm goals. There is no perfect scenario. Farms are recommended to work with experienced agronomists to assess the straw management options that best align with long and short-term goals.

Remove straw from the field

Maintain straw on field

¹ Harvesting Surplus Cereal Straw | Cereals: Barley, Wheat, Oats, Triticale | Government of Saskatchewan
² Increasing Cow/Calf Profitability Using Chaff and Chaff/Straw Feedstuffs. 2008. Alberta Agriculture, Forestry, and Rural Economics
³Increasing Cow/Calf Profitability Using Chaff and Chaff/Straw Feedstuffs. 2008. Alberta Agriculture, Forestry, and Rural Economics
⁴ Cereal Straw: a hidden value on your farm. 2019. Alberta Wheat and Alberta Barley Commissions
⁵ Straw Manufacturing in Alberta. 2020. Alberta Agriculture, forestry, and rural Economics
⁶ Equipment Issues in Crop Residue Management for Direct Seeding. 1999. Alberta Agriculture, Forestry, and Rural Economic Development
⁷ Plant Growth Regulators: What Agronomists Need to Know. 2018. Alberta Agriculture, Forestry, and Rural Economics
⁸ Performance Story: Effect of Cereal Crop Residue Distribution on the Following Year’s Canola Emergence and Yield — Sask Wheat Development Commission
⁹ Equipment Issues in Crop Residue Management for Direct Seeding. 1999. Alberta Agriculture, Forestry, and Rural Economic Development
¹⁰ Province of Manitoba | agriculture - Tillage, Organic Matter and Crop Residue Management (gov.mb.ca)

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Agronomic Management to Accelerate Maturity and Preserve Yield when Seeding is Delayed

1. Crop choice. Delayed seeding of cereals into late May and June may suggest the need to change to an shorter season crop type. However, all crop types generally decline in yield potential and quality as seeding is delayed. It is important to adjust expectations and implement agronomic practices specific to delayed seeding.
   
   

2. Select an early maturing variety. Later maturing varieties can increase the risk of harvest challenges when the season is shortened by delays. A wet or cool fall can amplify these challenges. The provincial seed guides are an excellent resource. Reach out directly to seed distributors and local seed growers to find out what your options are for finding seed and for information on variety performance in your geographic area.
   
   

3. Communicate with crop insurance. Seeding delays may impact eligibility for crop insurance. Connect with your crop insurance representatives to determine insurable crop options under your specific timeline.
   
   

4. Increase seeding rates. Higher seeding rates encourage more rapid maturation to preserve yield and crop quality in a shortened growing season. Preserving yield in a shorter growing season will require a higher seeding rate to maintain the same number of heads per square foot. Due to rapid maturation, less yield will come from other components that contribute to yield such as tillers, kernels per spike and kernel weight.
   
   

5. Seeding depth. As long as the seed has good seed to soil contact and adequate moisture, seed no deeper than necessary as this will reduce the number of days to emergence.
   
   

6. Fertility. Yield goals may be reduced from earlier plans. Adjust fertilizer rates accordingly for revised yield goals. Keep in mind that while less nitrogen fertilizer will reduce days to maturity, lowering rates too much will limit yields even more than the reduced yield potential from delayed seeding.
   
   

7. Fertilizer application. Consistently, fertilizer applied at seeding performs as good as, or better than other fertilizer application timings. However, in order to facilitate faster seeding operations, filling time can be reduced if some fertilizer is broadcast. Practice good fertilizer management, such as using slow-release fertilizers or incorporation of urea. Urease inhibitors or polymer coated urea will minimize the risk of volatilization losses from broadcast nitrogen fertilizer applications. Be sure to review the 4R nutrient stewardship guidelines to ensure appropriate management techniques are implemented.
   
   

8. Prepare for increased disease pressure. Fusarium head blight (FHB) is an ever-present risk and one that will increase with late seeding. Choose a variety with improved resistance. Rust risk can also increase with late seeding. Tools like the Prairie Crop Disease Monitoring Network can indicate the risk of rust, which should be combined with vigilant crop scouting and fungicide application if appropriate.
   
   

9. Foliar fungicide. A common perception is that the application of foliar fungicide will increase the number of days to maturity. However, research conducted across Western Canada by Dr. Turkington and colleagues determined the actual impacts of foliar fungicide on maturity to be minimal. Application of a flag leaf fungicide on barley variety AC Metcalfe at eight sites across the prairies over 2 years increased days to maturity by less than a day.
   
   

10. Plant growth regulators (PGRs). PGRs can help to manage lodging in wet conditions. PGRs have been associated with delayed maturity due to the changes they cause in natural levels in plant senescence hormones (Grossman, 1992). Under Alberta conditions, up to three days delayed maturity was observed but it is not consistent in all locations, years, or with all cultivars. Research led by Dr. Breanne Tidemann in Western Canada only resulted in delayed maturity in barley 15% of the time with trinexepac (Tidemann et al., 2020).
    
    

11. Forages/Winter Cereals. Even if late seeding is impossible, growing annual forage for feed may be an option to explore. Annual forage will generate some income, protect the soil from erosion and provide competition for weeds. Winter cereals like winter wheat and fall rye are options as well, but they should not be seeded too early, because winter hardiness will decrease.
    
    

Yield and Quality Expectations for Delayed Seeding

Manitoba Agricultural Services Corporation (MASC) has data on the yield response of delayed seeding over several years. Over the past 10 years, most annual crops seeded at the end of May would normally be about 80 to 90% of regular yields while further delays in seeding until the second week of June would yield about 60 to 70% yield of regular yields.

Except for soybean, which is still rare across the Prairies, canola appears to be the most stable crop for late seeding, with about 95% yield when seeded at the end of May and around 80% yield when seeded in the second week of June. However, Dr. Ross McKenzie led a study on irrigated crops in southern Alberta that found canola suffered the highest yield losses among the nine crops evaluated (McKenzie et al., 2011). It is unclear why there is such a contrast between the MASC data and the research in Alberta. Dr. Yantai Gan’s research out of Swift Current, SK found similar yield loss trends for several crops, with wheat yields being the most stable across seeding dates (Barker, 2008).

Figure 1. Average yield response by seeding date from 2010-2019, based on average yield reported to MASC. Used with permission. Original available online

Wheat and barley are early maturing crops, but are they ideally suited for late seeded acres?

The short answer for barley is ‘no’. Despite being one of the earliest maturing crops, barley is not ideally suited for late seeded acres, but it may have its place.

MASC data corresponds fairly closely to research focused on barley seeding dates. In a separate seeding date research trial led by Dr. McKenzie and colleagues in southern Alberta, they found seeding delays of 20 days resulted in about 20% reduction in grain yields (McKenzie et al., 2005). Further north, Drs. Juskiw and Helm found that seeding barley in mid-June decreased yields to 54 to 76% of the overall yield (Juskiw and Helm, 2002).

However, a Prairie-wide study led by Dr. John O’Donovan contrasted previous findings of barley yield loss with delayed planting, finding little difference on average. They found that 25% of the time, delayed seeding resulted in higher yields, while early seeding resulted in higher yields 38% of the time. Generally, the locations that favoured earlier seeding were in the south and those locations that favoured later seeding were in the north. This study also found that malting barley will generally result in better quality with earlier seeding as delayed seeding often, but not always, resulted in increased grain protein and decreased plump kernels. Feed barley may be the better option when planting late, because kernel plumpness was greater with late seeding only about 12% of the time, which is not ideal for malt selection (O’Donovan et al., 2012).

So, what about wheat? As a general rule, wheat is planted as early as possible as it is tolerant to cold and frost. Planting earlier increases yield by helping the plant avoid the effects of the dry and hot weather during grain fill. But, how does it fair when it is planted later?

In a study from Dr. Ross McKenzie conducted in southern Alberta, durum was more sensitive to seeding date then CWRS. Durum saw a 1.3% yield loss per day compared to CWRS at 0.8% decline for each day after April 30th.

This aligns with data from MASC which stated that after mid-May a 1% yield reduction per day is possible for spring cereals. Later seeding also affected crop quality. Grain protein concentration increased, but test weight was not affected (McKenzie et al., 2011).

Despite the trend to yield reduction, it is possible to still see good yields if the conditions are right for the rest of the season. This was evident in 2018 in South Dakota as their spring wheat plots were planted mid-May (late for South Dakota) and still averaged 69-75 bu/acre (Kleinjan, 2022). Similarly, after the 1997 flood in Manitoba, crops were seeded in mid-June and crops (wheat, barley, oats, flax, canola) yielded 86-102% of the previous four-year average (Manitoba Agriculture).

According to the data from MASC, if planting late, cereals are probably a better option than some crops such as flax or field pea. It is important to try to follow the agronomic recommendations such as seeding depth and rates to ensure the best possible yield outcome for the conditions.

We cannot always count on a long open fall, like in 2021, so managing with an expectation of normal fall frost dates makes sense. When seeding is forced to be late, adjust expectations and implement agronomic practices that will help to accelerate maturity and preserve yield.

This aligns with data from MASC which stated that after mid-May a 1% yield reduction per day is possible for spring cereals. Later seeding also affected crop quality. Grain protein concentration increased, but test weight was not affected (McKenzie et al., 2011).

Despite the trend to yield reduction, it is possible to still see good yields if the conditions are right for the rest of the season. This was evident in 2018 in South Dakota as their spring wheat plots were planted mid-May (late for South Dakota) and still averaged 69-75 bu/acre (Kleinjan, 2022). Similarly, after the 1997 flood in Manitoba, crops were seeded in mid-June and crops (wheat, barley, oats, flax, canola) yielded 86-102% of the previous four-year average (Manitoba Agriculture).

According to the data from MASC, if planting late, cereals are probably a better option than some crops such as flax or field pea. It is important to try to follow the agronomic recommendations such as seeding depth and rates to ensure the best possible yield outcome for the conditions.

We cannot always count on a long open fall, like in 2021, so managing with an expectation of normal fall frost dates makes sense. When seeding is forced to be late, adjust expectations and implement agronomic practices that will help to accelerate maturity and preserve yield.

References and Other Resources

• Seed Guides
  • Alberta
  • Saskatchewan
  • Manitoba
    
    
• Prairie Crop Disease Monitoring Network
  
  
• Turkington et al. 2015. The impact of fungicide and herbicide timing on foliar disease severity, and barley productivity and quality.
  
  
• Grossman. 1992. Plant growth retardants: Their mode of action and benefit for physiological research
  
  
• Tidemann et al. 2020. Effects of plant growth regulator applications on malting barley in Western Canada
  
  
• Manitoba Crop Insurance Seeding Date vs Yield Response
  
  
• McKenzie et al. 2011. Optimum seeding date and rate for irrigated cereal and oilseed crops in southern Alberta
  
  
• McKenzie et al. 2005. Fertilization, seeding date, and seeding rate for malting barley yield and quality in southern Alberta
  
  
• Juskiw and Helm. 2002. Barley response to seeding date in central Alberta
  
  
• O’Donovan et al. 2012. Effect of seeding date and seeding rate on malting barley production in Western Canada
  
  
• Barker. 2008. Seeding delays hurt some crops more than others. (Gan research)
  
  
• Kleinjan. 2022. Latest Recommended Planting Dates for Spring Wheat in South Dakota
  
  
• Manitoba Agriculture. Mitigating The Risks Of Delayed Seeding
  
  
• McKenzie et al. 2011. Optimum Seeding Date and Rates for Irrigated Grain and Oilseed Crops
  
  
• Mitigating the Risks of Delayed Seeding
  
  
• Late Planting Spring Cereals
  
  
• Fertilizer Considerations in a Wet Spring
  
  
• Impact of Spring Flooding on Soil Fertility in Manitoba
  
  
• Delayed Seeding & Wet Soils
  
  

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Integrated Pest Management

Establishing a competitive crop can significantly reduce weed pressure. IPM strategies such as scouting, early seeding date, higher seeding rates, narrower row spacing, and fertilizer placement can all improve a crop's ability to compete with weeds and may help reduce herbicide reliance ¹.

Field history and scouting are important when making pre-burn decisions, and even more so if herbicide availability is limited. Some tactics that can be implemented are:

• Scout fields for weeds and consider field history to determine weed pressure.
• Fields known to have higher weed pressure may need to take priority if herbicides are limited.
• Spraying early while weeds are small means they are easier to control. Early control of small weeds can prevent yield loss due to weed competition.

In addition to scouting, multiple strategies can be used to improve the crop's weed competitive ability. All crops have a “critical weed free period”, the window during which crops are most susceptible to weed competition for light, water, and nutrients. For spring cereals, the critical weed free period is the 1-3 leaf stage. It is important to keep weed pressure low until this period has passed, weed emergence after this period has a greatly reduced impact on yield, as the crop will have the competitive advantage. As mentioned above, spraying early has an added advantage - generally the weeds are smaller, so lower herbicide rates can be an option to control weeds.

Early establishment of cereals can increase the crop’s competitiveness with early emerging weeds. Research has shown that ultra-early seeding of wheat, which is the practice of seeding based on a soil temperature, (seeding when the soil first reaches 2.5°C at the depth of seeding), rather than an arbitrary calendar date, can improve yield and yield stability ². The study found that both yield and yield stability were highest with earlier seeding dates, high seeding rates (400-450 seeds/m2), and shallow seeding depths (2.5 cm). It is highly recommended for a dual, fungicide and insecticide, seed treatment be used when seeding in an ultra-early system.

While research has not been conducted on the impact of ultra-early seeding on weed pressure, early seeding of cereals may result in reduced weed competition during crop establishment and the critical weed free period, however more research is needed.

Increased seeding rates can also be used to improve crop competitiveness with weeds. For cereals, a seeding rate of 250-400 live seeds/m2 is adequate to provide weed competition.³ Increased seeding rates, when moisture is adequate, can also result in reduced tillering and earlier maturity.

Although it is very unlikely an operation will be able to change equipment as quickly as global markets impact crop protection products, row spacing is another tactic that can be considered to improve crop competitiveness. Narrow row spacing in cereals can provide a competitive advantage with weeds. Narrow row spacing promotes quicker canopy closure, which will reduce the ability of weeds to compete for resources.

Herbicide Alternatives and Tank Mixes

If herbicide quantities are limited, producers may need to prioritize fields for pre-burn spray applications based on field specific weed spectrum and pressure. Fields with higher weed pressure or larger weeds may require higher rates of glyphosate, or the inclusion of a tank mix partner. The addition of a tank mix partner (see Table 1 for tank mix options), can be useful for improved weed control, managing herbicide resistance, and reducing the rate of glyphosate needed. If weed spectrum allows, it may be possible to reduce the glyphosate portion of the tank mix from 1 REL (Roundup Equivalent Litre) to 0.5 REL or lower.

Consult the product label for recommended herbicide rates; it is not recommended to reduce product rate below the recommended guidelines. This could lead to reduced efficacy and increase the risk of polygenic herbicide resistance. Lower rates of glyphosate may require application adjustments such as lower water volumes and the addition of a non-ionic surfactant (ex. Ag SurfⓇ II, AgralⓇ 90), which is on-label for lower rates of glyphosate. The non-ionic surfactant can increase the ability of glyphosate to penetrate the plant cuticle for absorption. If glyphosate is used with a tank mix partner, higher water volumes may need to be maintained.

Be sure to contact your retailer and confirm the status of pre-order herbicides to confirm their delivery. If certain herbicides are not available, growers should consider alternative plans. For example, if glyphosate is not available for all pre-burn acres, different herbicide groups should be considered. In these considerations, crop tolerance, weed spectrum, and re-cropping restrictions should also be factored in. If there are limited glyphosate supplies, growers will need to re-balance their herbicide program and decide if a reduced supply of glyphosate should be reserved for Round-Up Ready crop acres or if it needs to be used for pre-burn applications. If glyphosate is dedicated to pre-burn applications, and glyphosate is unavailable for in-crop canola or soybean applications, then more traditional chemistries will need to be used. These decisions will be field specific decisions based on the weed spectrum, resistance management and re-cropping restrictions. Your provincial crop protection guide contains herbicide selection charts to help growers consider their herbicide options for different weed spectrums in various crop types.

Saskatchewan Guide to Crop Protection

Manitoba Guide to Crop Protection

Alberta Guide to Crop Protection

Table 1: Herbicides to Control Emerged Weeds Before Seeding or After Seeding but Prior to Crop Emergence

_{Information Sourced from 2022 Guide to Crop Protection. Saskatchewan Ministry of Agriculture}

Tillage

Tillage can be used to control weeds prior to seeding. It is important to recognize that moisture will be limiting for many areas on the prairies this spring. Any soil disturbance, including heavy harrow can increase moisture loss. Additionally, soil disturbance (such as tillage) can increase weed seed germination, therefore multiple passes may need to be utilized. The first tillage pass will stimulate weed growth by aerating and warming the soil, the second pass can be used to control weed growth. Tillage increases moisture loss and erosion and can significantly impact crop establishment. In general, this is not a recommended weed control practice.

Spraying technologies

Increasing spray efficacy and reducing waste of herbicides is an important consideration. Spray water quality, droplet size, and speed are all important factors when it comes to herbicide efficacy. Poor spray water quality can impact herbicide efficacy. Glyphosate can be significantly impacted by hard water. More information regarding spray water quality can be found here. Another consideration to ensure maximum efficacy of pre-burn herbicides is droplet size: according to Sprayers101, finer sprays should be used for tank mixes that contain contact herbicides (group 1,6,10,14, 15, 22, 27) and herbicides that target grassy weeds.⁴

Spraying speed can also impact herbicide efficacy; in general, slower travel speeds result in more even spray deposition and better weed control. In addition to ensuring adequate spray efficacy, it is also important to consider ways to reduce spray waste. Reducing sprayer overlap with sectional control, priming the boom using sectional control or a recirculating boom, use of an accurate herbicide metering device, and only mixing the amount of spray needed for field size are all small ways that can significantly reduce herbicide waste. More information can be found at Sprayers101.

With increasing herbicide costs and potential for herbicide shortages new spraying technologies such as spot spray may pencil out better in your budget this year than previously. Spot spray technologies such as WEEDit Quadro, Trimble WeedSeeker, and John Deere See & Spray Select can be utilized to reduce herbicide usage at burn-off. These technologies utilize selective spraying technology to only apply spray to green plants. They can significantly reduce herbicide usage in a pre-burn application, and with rising herbicide costs these technologies start to pay for themselves faster. At this time, the technology cannot selectively spray weeds within a crop, however the technology is rapidly advancing.

Planning Ahead

Good communication with retailers and booking herbicide early can significantly increase chances of getting the products needed. Retailers will be best able to give reliable estimates of product availability if you are straight-forward when herbicide shopping.

Clear and early communication gives you the time needed to make adjustments to your plan, including alternative products, adjusting rates where appropriate and making some investments in technology that can reduce herbicide usage. Seeding and spraying is go-time, so downtime waiting for herbicides that are not available will be frustrating and more impactful on yields and the bottom line than making some strategic adjustments in the last few weeks before seeding.

Summary

If herbicides are in short supply, the following list can be used to assist with herbicide management considerations on-farm:

1. Utilizing seeding BMPs that encourage development of a competitive crop?
2. What is the field history for weed pressure?
3. Take stock of available herbicides, what is incoming, and what is unknown to arrive. What is the worst-case scenario of products getting on the farm? Have all available retails been contacted?
4. Under the different scenarios, how short is the farm on required herbicide products?
5. Do certain require higher glyphosate rates based on expected weed pressure? Can tank mixes or replacement products supplement weed control where extra control is required?
6. Can in-crop glyphosate be replaced with conventional herbicide protection products?
7. Are BMP spray techniques being implemented to ensure what efficiently and effectively herbicide application?
8. Can spot tillage be utilized?
9. Is full-field tillage (worst case scenario) the only remaining option?

Additional Resources:

Spray Water Quality: https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/weeds/water-quality-and-herbicides

Dealing with Pesticide Shortages in 2022, Sprayers101 https://sprayers101.com/dealing-with-pesticide-shortages-in-2022/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7020467/

Wheat and Barley Target Seeding Rates: https://www.albertawheatbarley.com/the-growing-point/articles-library/wheat-and-barley-target-seeding-rates?back=1094

Endnotes:

¹ Saskatchewan Ministry of Agriculture. n.d. “Organic Crop Production Weed Management.” Saskatchewan. Accessed 03 10, 2022. https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/organic-crops/organic-crop-production-weed-management

² Collier, G.R.S.; Spaner, D.M.; Graf, R.J.; Beres, B.L. Optimal Agronomics Increase Grain Yield and Grain Yield Stability of Ultra-Early Wheat Seeding Systems. Agronomy 2021, 11, 240. OPEN ACCESS: https://doi.org/10.3390/agronomy11020240

³ Lemerle, D, R Cousens, G Gill, S Peltzer, M Moerkerk, C Murphy, D Collins, and B Cullis. 2004. “Reliability of higher seeding rates of wheat for increased competitiveness with weeds in low rainfall environments.” The Journal of Agricultural Science 395-409.

⁴ Wolf, Tom. 2022. “Dealing with pesticide shortages in 2022.” Sprayers101. 02. Accessed 02 25, 2022. https://sprayers101.com/dealing-with-pesticide-shortages-in-2022/

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Why Invest in a Seed Test?

Seed is the foundation of every crop and the best way to determine its quality is through a simple seed test. Without a seed test, once a seed issue is realized, significant costs will have been incurred and the yield potential of that crop or from re-seeding another crop will have declined. Environmental conditions in the year the seed is grown impact its quality. Seed grown and harvested in a drought year can have significant quality impacts, just as seed grown in a wet year. Furthermore, seed quality can change after long periods of storage and, therefore, seed testing is a meaningful investment and planning tool ahead of every season.

Seed Test Interpretation

Germination

Germination describes the percent of seed that is likely to germinate under optimal and standardized oxygen, light, moisture, and temperature conditions. Germination is an accredited test; cereals undergo a brief cold period to break dormancy and are then tested at 20°C for seven days. There is no pre-chill requirement in chickpea, lentil, or pea crops but the temperature is also held at 20°C with final counts performed seven days later. At the end of this test period, seeds are evaluated and placed into various germination categories including fresh, hard, abnormal, and dead seeds.

• Fresh seeds fail to germinate. These seeds will imbibe water regularly and initially appear to be capable of germination but then remain dormant. Fresh seeds may be viable but cannot be confirmed.

• Hard seeds fail to germinate. The seed coats of hard seeds will not be penetrated by water and remain intact at the end of the test period.

• Abnormal seeds germinate, but do not have adequate plant structures to maintain healthy growth such as missing roots or shoots.

• Dead seeds cannot produce any part of a seedling. They may imbibe water and crack the seed coat but will die before they will produce seedlings. Higher levels of seed-borne disease usually correlate to a higher percentage of dead seeds.

The germination test is useful, as it tells us the maximum potential of the seed lot under optimal conditions. This information can be used to determine if, under ideal growing conditions, a particular seed source should be planted at all. However, germination is only a single component of seed quality. When germination is poor, a different seed source may be selected. When germination is good, the decision to plant a seed lot should not be based on germination alone. Germination is largely influenced by late-season environmental conditions, and harvest weather that is too cold, too wet, too hot or too dry can all reduce germination.

Germination can also be negatively impacted by applications of pre-harvest glyphosate and therefore it is not recommended to plant seed that has been treated with pre-harvest applications of glyphosate as chemically damaged seed may show lower germination values, poor root development, and higher than acceptable levels of seedling mortality. Exceptional circumstances may result in a desire to test seed that has been treated with pre-harvest glyphosate that was applied at the proper timing. Seed labs can estimate germination of seed treated with pre-harvest glyphosate if the germination test is done in soil. Submitting a seed sample that received pre-harvest glyphosate will result in abnormal seedling development, inaccurate results, and the seed lab will have to redo the test, costing extra. The risks mentioned above are still valid, so it is recommended to source seed elsewhere instead of using treated with pre-harvest glyphosate.

Vigour

The vigour test measures a seed lot’s ability to produce normal seedlings under adverse conditions. Unlike the germination test that is run under optimal conditions, vigour is most often measured using a cold stress test which evaluates the seedlings’ ability to withstand cool temperatures (5ºC for seven days) and accompanying stress that may be typical of early spring planting. Vigour in a seed lot is important because it may provide insight into how seedlings will perform under challenging conditions. Seed lots with higher vigour seed lots may have faster and more uniform seedling emergence in low-temperature soils or other stressful conditions.

Low vigour values may also provide an early warning of diminishing seed quality as seed lots will begin to drop in vigour before germination values start to fall. Conditions of seed development, maturation, storage, and seed aging, all impact vigour. Seeds developed under moisture stress, nutrient deficiency, or extreme temperatures are often characterized by light, shrivelled, and low-vigour seed. Similar to germination, vigour will also be negatively impacted by mechanical damage or improper storage.

The vigour test is not standardized among seed labs. While the cold stress test is common, the parameters and the stress used may vary between labs. Vigour tests from different labs should not be compared directly.

Seed-borne Pathogens

Fungal screening for seed-borne pathogens is an important component of assessing seed quality as these diseases can have negative impacts on crop establishment, overall plant health, and ultimately crop yield. Evaluation of seed-borne pathogens is particularly important for diseases that have high rates of seed-to-seedling transmission. For example, Ascochyta rabiei carried on chickpea seed is readily transmitted to the seedling and can be highly destructive to the crop. Therefore, only chickpea seed lots with low infection levels (<0.3%) data-preserve-html-node="true" are acceptable for planting. Even if this threshold is met, a seed treatment is still recommended as the likelihood of missing an infected seed is very high and even a very small percentage of Ascochyta-infected chickpea seed can result in significant seedling infection.

Seed treatments are an excellent tool to help protect cereal and pulse seedlings against early-season soil and seed-borne pathogens. Seed treatment selection should be based on the targeted pathogens of concern and should be applied by means to ensure thorough seed coverage and according to label instructions. Some seed treatments may not be compatible with certain seed-applied rhizobium inoculants, so it is recommended to consult with manufacturers for compatibility information. It is important to note that seed treatments alone cannot compensate for a poor seed lot and some seed lots simply have too high of disease levels to be used as a seed source. Guidelines have been developed to help inform decisions of acceptable thresholds for seed-borne pathogens, but guidelines are only guidelines. Soil moisture and temperature conditions following planting will also influence what infection levels are tolerable in a given year or location. There are no hard rules on acceptable levels of disease due to each producer having a unique situation and acceptable level of risk.

¹Adapted from Saskatchewan Ministry of Agriculture guidelines
² Additional information on thresholds for Fusarium graminearum is available from the Saskatchewan Ministry of Agriculture

Thousand Kernel Weight

The thousand kernel weight (TKW) is a measure of seed size and represents the weight, in grams, of 1,000 seeds. Seed weight may also be reported, which is the weight of a single seed, in milligrams, and is numerically equivalent to TKW. Most crops have a typical TKW range but it is important to note that TKW is unique to each individual seed lot and can vary substantially between varieties, fields, and growing seasons. For instance, smaller and lighter seed with lower TKWs is often a consequence of a drought season when limited moisture resources did not allow for optimal seed fill.

Measuring the TKW of a seed lot is important for calculating the optimal seeding rates for pulse and cereal crops as it provides a more precise measurement of seeds sown compared to bushels or weight. Providing that all seed quality factors are equal between two seed lots, the seed source with the higher TKW will require a heavier seeding rate to achieve the same optimal plant stand. This is because the bigger the seed, the higher the TKW and the fewer seeds per pound. Therefore, for the same weight (i.e. 60 pounds) of seed, fewer potential plants are being put in the ground.

Optimal Plant Stands and Seeding Rate Calculations

Targeted Plant Population

Plant population is an important factor for the establishment of competitive, high-yielding cereal and pulse crops. Optimal plant stands differ by crop, environment, and management factors but care should be taken to target appropriate plant densities for each individual crop and farm operation.

Calculating Seeding Rate

Once the desired plant population is determined the seeding rate can easily be calculated based on specific seed quality parameters of each individual seed lot. Although this calculation is fairly straightforward, the seedling survivability rate can be difficult to estimate and will vary among farms and across the growing season. As a general rule of thumb for cereal and pulse crops, expected seedling survivability is approximately 5‒15% lower than the germination rate with a lower survivability rate anticipated under adverse growing conditions.

Factors to consider when assigning seedling survivability include:

• Seeding date
• Soil temperature, moisture, and texture
• Seed handling and seeding speed
• Seeding depth
• Seed placed fertilizer
• Seedling pests such as insects and soil-borne pathogens

Increased seeding rates will be required to overcome low seedling survivability; however, it is important to recognize that not all issues of poor quality seed can be corrected by increased seeding rates. For instance, large differences in vigour and germination values in a seed lot can be exacerbated by increasing seeding rates which may impose greater variability in establishment and lead to a more uneven plant stand. Similarly, increasing the seeding rate to overcome low germination of a seed lot with a high pathogen load will simply introduce more disease into the field.

Value of Seed Testing in a Dry Year

Seed grown during a dry year typically boasts lower disease levels relative to an average or wet season, but reductions in seed-borne pathogen load do not guarantee high-quality seed. Particularly impacted are germination, vigour, and TKW with potential reductions in all categories.

• TKW: When seeds do not have adequate moisture resources during grain fill, final seed production is typically much lower than expected crop averages
• Vigour: Production of gibberellin hormone, responsible for regulating seed maturity and dormancy, is typically reduced under drought conditions and seed may demonstrate higher than anticipated levels of dormancy and lower vigour as a result. Grain, particularly pulses, harvested during very hot and dry conditions can be susceptible to micro-cracking on the seed coat leading to reductions in vigour before germination levels are noticeably affected.
• Germination: mechanical damage from typical harvest and handling activities is often increased under hot and dry conditions, especially when the seed moisture content is low and air temperatures are high. Such damage to the seed coat can have a significant negative impact on germination levels with pulse crops being the most prone to seed coat cracking and splitting.

Initial seed testing reports from the fall of 2021 are indicating low germination in some crops, particularly in field pea. Field pea samples experienced high levels of mechanical damage during harvest operations and some labs are reporting the majority of pea samples with sub-optimal germination levels.

Provincial Seed Survey

Each year, the Saskatchewan pulse and cereal commissions partner with commercial seed testing laboratories to complete an annual survey of seed-borne pathogens measured on seed grown in Saskatchewan during the previous season. All labs that offer seed testing services to Saskatchewan growers are invited to participate in the annual survey with anonymous reporting of results amalgamated by crop district from all participating labs. Interim seed quality data, collected from the time of harvest to the end of December, are summarized and communicated to growers, agronomists, researchers, and industry during the winter months, ahead of the next crop season. These interim results provide insights into seed quality trends and identify potential hotspots for seed-borne pathogens across the province. A final summary of results, including data from seed samples analyzed after the interim results, is reported at the end of May. This final summary is submitted for publication in the Canadian Phytopathological Society Canadian Plant Disease Surveys. This publication of the provincial survey provides a record of seed-borne pathogen trends in pulse and cereal crops and allows for continued tracking of diseases over time.

Acknowledgments

The provincial seed survey would not be possible without the participation of 20/20 Seed Labs Inc., Discovery Seed Labs, Prairie Diagnostic Seed Labs, and Lendon Seeds. Thank you to all lab partners for their continued effort and support of this project. Brian Olson, independent contractor, is also gratefully acknowledged for his coordination of the seed quality survey and summarization of results. A special thanks is also extended to Dr. Randy Kutcher and Dr. Sabine Banniza from the University of Saskatchewan for their external review and pathology expertise. External review efforts of Alireza Akhavan, Provincial Plant Disease Specialist, and Dale Risula, Provincial Special Crops Specialist, of the Saskatchewan Ministry of Agriculture (SMA) is also recognized with an extra note of appreciation to Alireza Akhavan and the SMA Geographic Information System (GIS) team for creating the seed-borne pathogen maps by crop district.

Pulses: 2021 Interim Results

The interim results of commercial plate tests for seed-borne pathogens of lentil, field pea, and chickpea samples reveal a high number of pathogen-free seed samples from across the province. Results to date suggest an overall decrease in mean severity and infection levels of seed produced during the 2021 growing season compared to results from 2020 and is among the lowest mean infection levels and the highest percentage of pathogen-free samples in the past seven years.

• Greater than 96% of lentil samples were free of seed-borne pathogens; samples that did have detectable levels of Ascochyta, Anthracnose, or Botrytis had a mean infection level below 1%
• Seed-borne Sclerotinia was not detected on any pulse samples.
• Seed-borne Botrytis was detected on less than 1% of lentil and field pea samples, but was identified on 9.7% of chickpea samples; mean infection levels were 0.5% or lower for all pulse samples.
• Seed-borne Ascochyta was detected on 25.1% of field pea samples, but mean infection levels (1.1%) were well below critical threshold levels.
• 27.1% of chickpea samples had detectable levels of seed-borne Ascochyta. On average, the level of infection was 1.3% and exceeded the critical threshold of 0.3%.

The distribution of submitted samples and crop districts reporting seed-borne pathogens varies across the province. Although the maps created by the Saskatchewan Ministry of Agriculture can help identify areas of lower risk of seed-borne disease, testing of individual seed lots is still recommended.

Figure 1. 2021 Interim Seed Test Result for Seed-Borne Anthracnose in Lentil. Source: Saskatchewan Ministry of Agriculture

Figure 2. 2021 Interim Seed Test Result for Seed-Borne Ascochyta in Field Pea. Source: Saskatchewan Ministry of Agriculture

Figure 3. 2021 Interim Seed Test Result for Seed-Borne Ascochyta in Chickpea. Source: Saskatchewan Ministry of Agriculture

Cereals: 2021 Interim Results

The interim results of commercial plate tests for seed-borne Fusarium pathogens reveal very low mean infection levels barley, durum, oat, and wheat samples tested as of December 28, 2021. The percentages of total Fusarium spp. and F.graminearum-free samples are trending higher across all cereal samples relative to the two prior seasons.

• F.graminearum was not detected on oat samples.
• F.graminearum was detected on less than 4% of barley, and wheat samples, but was identified on 20.1% of durum samples; mean infection levels were 1.1% or lower for all cereal samples
• The highest percentage of total Fusarium spp.-free samples were in durum (44.7%), followed closely by wheat (41.6%); durum and wheat also had the lowest mean infection levels of total Fusarium spp., 1.7% and 2.3%, respectively.
• The majority of oat samples (94.6%) had detectable levels of total Fusarium spp. with a mean infection level only slightly lower than that measured in 2020 (7.5%).
• 81.1% of barley samples reported a detectable level of total Fusarium spp.; however, the mean infection level to date is below those measured in 2020 or 2019.

Despite overall low levels of Fusarium-infected cereal seed lots being reported in interim results, seed quality does vary by crop districts as detailed by maps created by the Saskatchewan Ministry of Agriculture and it is recommended that seed lots should be tested on an individual basis.

Figure 4. 2021 Interim Seed Test Result for Total Seed-Borne Fusarium in Barley. Source: Saskatchewan Ministry of Agriculture

Figure 5. 2021 Interim Seed Test Result for Total Seed-Borne Fusarium in Durum. Source: Saskatchewan Ministry of Agriculture

Figure 6. 2021 Interim Seed Test Result for Total Seed-Borne Fusarium in Oat. Source: Saskatchewan Ministry of Agriculture

Figure 7. 2021 Interim Seed Test Result for Total Seed-Borne Fusarium in Wheat. Source: Saskatchewan Ministry of Agriculture

Seed Test for Crop Success

Seed is arguably the most valuable input for any crop and ensuring its quality is of utmost importance, regardless of the season. Although interim seed survey results show historically low levels of mean pathogen infection and high proportions of disease-free seed, other seed quality parameters such as germination and vigour may have been compromised due to increased levels of mechanical damage during a season characterized by extended periods of extremely hot and dry conditions. Seed testing in the fall is a great way to evaluate the seed quality potential of the seed source on the farm, but seed testing for germination, vigour, and TKW should also be repeated in the spring to ensure no significant changes have resulted after extended storage and further handling. Final seed test results should be used to fine-tune seeding rate calculations to target optimal plant stands and help get the crop off to the best start possible in the spring.

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When scouting fields in the spring there can be many reasons for poor or patchy emergence. Fields that seem to be slow to emerge, have a high presence of birds, or have had insect issues in the past are fields that warrant a closer look.

Wireworms

Wireworms are the larval stage of click beetles. These larvae can cause significant damage to wheat crops through feeding on germinating seeds and young seedlings. The insect is attracted to germinating seeds by the CO2 given off during respiration. The most common species of concern are prairie grain wireworm, Ctenicera destructor, and Hypnoidus bicolor.

Scouting: look for bare patches, severed or wilted plants, shredding of stem below ground, patchy/poor emergence. Wireworm damage can appear as shredded stems (below- ground) and/or holes bored into seeds. Once you have identified a potential area of damage, dig around and look for the larvae. Wireworms do most of their feeding early in the spring while they are closer to the surface. Bait balls can also be an effective tool, prior to seeding, to indicate the presence of wireworms.

ID: wireworms have slender cylindrical bodies (10-20mm long) with three pairs of legs on the thorax. They are white to yellowish and have a keyhole-shaped notch on the last segment of the abdomen (Figure 1).

_{Figure 1. Wireworm larvae in soil. Source: Haley Tetreault, Sask Wheat}

Management: unfortunately, there are no control options once the crop has been seeded, so it is important to make record of fields with wireworm damage. Consider the use of insecticidal seed treatment in fields with a history of wireworm damage. Foliar insecticides will not provide control.

Economic Threshold: none established

Cutworms

There are many different species of cutworm, however the two that are the most dominant, which can cause issues in wheat are the pale western cutworm (Agrotis orthogonia) and the redbacked cutworm (Euxoa ochrogaster). Both species of cutworm overwinter as eggs in the top centimeter of soil and larvae emerge in early May. These species feed on lower leaves early in the season and, cut plants below ground as they mature and increase in size. Many cutworm species are nocturnal feeders; scouting for species that feed above ground should be done in the evening when they are active.

Scouting: Begin scouting when the crop emerges. Cutworms are often worse on sandy ridges and eroded knolls. Look for bare spots and thinning areas- which will expand with continued feeding. Look for severed or yellowing plants. Examine the top 2-5cm of soil around a severed plant, or on the edge of a bare patch, near healthy plants. These insects will not remain in areas without plants to feed on. Look for feeding damage; cutworms more often cause complete severing of the plant or leaf, whereas wireworms shred underground stems. Birds are attracted to fields with higher populations of cutworms and can be a signal to examine fields further. Scout for cutworms from crop emergence until mid June.

ID: Redbacked cutworms are above ground feeders when small; during the heat of the day, they hide under debris. As they mature, feeding occurs underground. The are fleshy caterpillars with a brick or reddish-brown coloured strip that runs along their back bordered by a dark strip on each side (Figure 2).

Pale Western cutworms are also foliar feeders when young and change to subterranean feeding as they mature, which means they feed below ground and pull leaf tissue below the soil surface to feed. They are fleshy caterpillars with a yellowish-brown head that has two vertical markings, and a pale white-grey body with no distinct markings (Figure 3).

Management: Spray infested areas in the morning or evening when cutworms are actively feeding. Subterranean cutworms that do not contact insecticidal residue on soil surface or toxins incorporated into plant tissue, will be exposed when pulling plant material below ground to feed. This effect depends heavily on the insecticide used to control. Pyrethroid residues are not long-lived in the environment. If a field needs to be reseeded, spraying insecticide prior to re-seeding or using a diamide-containing seed treatment is recommended, if cutworms are still present and active in significant numbers.

Economic Threshold:

Redbacked 5-6 larvae/ m²

_{Figure 2. Redbacked cutworm. Source: John Gavloski, Manitoba Agriculture}

Pale Western 3-4 larvae/m²

_{Figure 3. Pale western cutworm. Source: Frank Peairs, Colorado State University, Bugwood.org}

Grasshoppers

Grasshoppers can cause significant damage in wheat; however, the 2021 grasshopper forecast is calling for relatively low population densities across the province. This map can be found here. Grasshopper populations are affected by environmental conditions. Grasshopper damage tends to be most significant in hot, dry years. The species of most concern in wheat production are the migratory grasshopper (Melanoplus sanguinipes) and the clear-winged grasshopper (Camnula pellucida). Migratory grasshoppers feed on both broadleaf plants, and grasses. Clear-winged grasshoppers prefer cereal grains. It is important to identify which species of grasshopper is present, as not all species cause economic damage. Grasshoppers are not usually “early season” pest, however monitoring populations as they emerge is important.

Scouting: eggs hatch in May when soil temp reaches 4.5°C. Scout along field margins and sloughs. Start from a headland and work your way in towards the centre of the field; populations are often highest on field borders. Although nymphs can be damaging, these events are relatively uncommon. Like many highly fecund animals, the vast majority of the young are not going to survive to adulthood. If the nymphs are not causing damage, do not control them but rather, continue to monitor.

ID: There are 85 species of grasshoppers in Saskatchewan. Only about five cause economic damage and only do so at high densities, so species identification is very important.

Migratory Grasshopper

Nymphs: mottled grey body with a stripe across the head Adults: greyish-brown with a black stripe across the head. A series of black bands on hind legs. (Figure 4)

_{Figure 4. Migratory grasshopper. Photo by Dr. Dan Johnson, University of Lethbridge}

Clearwinged grasshopper

Nymph: tan with a white band that goes around the thorax Adult: yellow or brownish body with clear wings with some dark patches. This species also has two stripes running along its back, but the stripes start at the thorax and meet at the wing tips. (Figure 5)

_{Figure 5. Clear-winged grasshopper. Photo by Dr. Dan Johnson, University of Lethbridge}

Management: If economic threshold is reached there are many insecticidal sprays and baits, and biologicals available for control. Insecticide rate will depend on grasshopper size and product used, which can be found in the Saskatchewan Guide to Crop Protection.

Economic Threshold: 8-12 grasshoppers/m² in wheat

Additional Reading and Information

Prairie Pest Monitoring Network https://prairiepest.ca/

Field Guide of Pest Wireworms in Canadian Prairie Crop Production,” written by Haley Catton, Wim van Herk, Julien Saguez, and Erl Svendsen SOON TO BE RELEASED

Wheat School on how to make bait balls for wireworm scouting: https://www.realagriculture.com/2012/04/wheat-school-how-to-make-wireworm-bait-balls/

Grasshoppers in Saskatchewan https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/insects/grasshoppers

Grasshopper Identification and Control Methods to Protect Crops and the Environment. Dan Johnson.

Cutworm Pests of Crops on the Canadian Prairies: Identification and Management Field Guide. Floate, K.D. 2017

Field Crop and Forage Pests and their Natural Enemies in Western Canada: Identification and Management Field Guide. (extensive author list)

Information in this resource was sourced from the following sources:

Floate, K.D. 2017. Cutworm pests on the Canadian Prairies: Identification and management field guide. Agriculture and Agri-Food Canada, Lethbridge, Alberta

Cutworm Pests of Crops on the Canadian Prairies: Identification and Management Field Guide

Philip, H., B.A. Mori and K.D. Floate. 2018. Field crop and forage pests and their natural enemies in Western Canada: Identification and management field guide. Agriculture and Agri-Food Canada, Saskatoon, SK

https://prairiepest.ca/wp-content/uploads/2019/01/AAFC-Field-Guide_ENGLISH_HQ_Print_new-cover_June-2018.pdf

Saskatchewan Ministry of Agriculture. Grasshoppers. https://www.saskatchewan.ca/business/agriculture-natural-resources-and-industry/agribusiness-farmers-and-ranchers/crops-and-irrigation/insects/grasshoppers

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Barley is less resilient and will exhibit frost damage at temperatures closer to -4°C to -6°C (R. McKenzie, personal communication). Minimal frost tolerance research on barley has been conducted. However, the chance of plant death is low at these temperatures, especially when soil temperatures are warmer. Warmer soil, and especially moist soil, is buffered from temperature changes which helps to protect the growing point of cereals from late spring frost. This is due to wheat and barley plants having their growing point under the soil surface until stem elongation (begins after the 3 leaf stage and tiller initiation) when the inflorescence, or developing head, begins to move above the tillering node. The growing point of the plant must be damaged for the plant to die. For this to happen, extended time periods below freezing would need to occur. If only the leaves are damaged, the plant can grow back from that protected growing point, but the crop will be delayed.

_{Figure 1 - Emerged wheat seedlings with frost crystals}

It is also possible for plants that have already encountered cold environmental conditions (hardened-off) to better tolerate frost due to changing the plant’s physiology and biochemistry to increase cold tolerance. Most frost damage is caused by ice crystals that injure cell membranes. Even if plant tissue is frozen, it does not necessarily mean that the tissue is severely damaged (Forbes and Watson, 1992). Some damage can be avoided by the plant moving water outside their cells so that ice crystals form between cells (rather than within cells) which causes less damage to cell membranes. Spring wheat can concentrate salts in their cells to lower the freezing point slightly below 0°C. Acclimatized winter wheat can survive temperatures well below freezing by forming ice crystals between cells and creating a high solute concentration in their cell sap which acts as an anti-freeze. Consider this the plant’s natural defence system.

It is important to keep in mind that frost’s impact on crop survival will vary greatly due to factors such as: soil texture, soil moisture, topography, speed of temperature drop, duration of freezing temperature, residue coverage, crop growth stage, etc. Additionally, minimal research has been done looking specifically at what temperatures are required to cause plant or leaf death under these various factors. Due to all of these factors, it is extremely difficult to identify thresholds of risk for wheat and barley crops.

When do I start assessing damage after a frost?

After experiencing cold temperatures, it’s important to assess the impact. Patience is needed before you can provide a proper diagnosis of the damage. Leaf and below-ground plant material may take three to four days to display the full impact of frost damage. Scouting the field too soon can give misleading results as the first few days after a frost may not display damage.

Checking plant stand and survivability

Wheat plants affected by frost will turn a dark green colour and appear water-soaked after a couple of days. Following this, leaves will begin to turn necrotic and die. However, this does not mean the plant is dead. If the plant has survived, it will begin to produce new leaves after four to five days in warm conditions. If you dig up the plant, you may also see new root development. During overcast and cool conditions, it may take a few more days to see regrowth. If you are not seeing new leaves develop, dig up plants and check for survival at the growing point. When you pull up the plant, look at the crown of the plant (the area where the leaves and the roots meet) and check to see if the area is white and alive with plant tissue (Figure 2) or dark brown and soft/wet. If the crown is dark brown and soft/wet, the plant will not likely survive.

_{Figure 2 - Wheat seedling with a healthy growing point}

If you find a large number of plants that haven’t survived, you will want to assess your plant population and determine if action needs to be taken.

How does a reduced plant stand impact yield and quality?

Research conducted on spring wheat can provide us with an indication of yield loss due to decreased plant stands. Research by Chen et al. (2008) indicated that a plant stand of 89.3 plants/m2 (8.3 plants/ft2) was 15.7% lower yielding than 249 plants/m2 (23.1 plants/ft2). Research by McKenzie et al. (2011) indicated that a CPSR wheat plant stand of 76 plants/m2 (7 plants/ft2) resulted in a 15.7% decrease in yield compared to 272 seeds/m2 (25 plants/ft2). The same study also demonstrated that a CWRS wheat plant stand of 76 plants/m2 (7 plants/ft2) resulted in a 10% decrease in yield compared to 272 plants/m2 (25 plants/ft2).

For barley, research has indicated that lower plant stands may be less impactful to crop yield. Research conducted by McKenzie et al. (2005) indicated that a plant stand of 109 plants/m2 (10.1 plants/ft2) only decreased yield by 5.6% compared to 190 plants/m2 (17.6 plants/ft2). In a separate study, O'Donovan et al. (2012) saw a yield decrease of approximately 10% at a seeding rate of 100 seeds/m2 (9.3 seeds/ft2) compared to 300 seeds/m2 (27.9 seeds/ft2).

Although the reduced plant stands display yield decreases that are not large in magnitude, there are high risks involved with low plant populations. First, consistency in crop performance drops at low seeding rates. In other words, you can expect much more year-to-year yield variability with low plant stands. This was demonstrated by Collier et al (2021) where seeding rates of 200 seeds/m2 (18.5 plants/ft2) compared to 400 seeds/m2 (37.1 plants/ft2) had lower yields, greater yield variability, or both (Figure 3).

_{Figure 3 - Demonstration of the relationship between seeding rate and depth of CWRS wheat in Western Canada as it relates to yield and variability (Collier et al., 2021). Numbers 200 and 400 represent the seeding rate in seeds/m2. ‘Shallow’ or ‘Deep’ represents seeding depths of 2.5cm or 5cm. Group I - high mean grain yield and low variability – what growers want to be targeting; Group II - high mean grain yield and high variability; Group III - low mean grain yield and high variability; Group IV - low mean grain yield and low variability}

The yield losses from the reduced plant stands, as mentioned above, are collected from small plot research. In these small-plot scenarios, weeds are kept to a minimum to reduce plot-to-plot variability. Therefore, the management of yield-robbing weeds does not reflect what may be seen across an entire field. The impact on yield that frost-induced variability can cause may not be fully realized within small-plot research.

With lower plant stands, one can expect the crop will be less competitive against weeds. For this reason, a field with a low plant stand will require even more attention to detail and timely herbicide applications to reduce the risk of weeds impacting crop performance. Additionally, , lower plant stands will extend the amount of time a crop takes to reach maturity and increase the number of tillers present on each plant. These factors, depending on how the rest of the season plays out, will impact the timing of a pre-harvest herbicide application, the timing of harvest, and may also impact quality. Make no mistake, higher plant stands provide higher yields, more consistent yields, better quality and more weed competition more often than lower plant stands.

Reseeding considerations

Keep in mind that the calendar date needs to be considered when discussing reseeding of wheat or barley. According to McKenzie et al. (2011) CWRS wheat and feed barley crops lose an average of 0.8% and 1.3% yield, respectively, when seeded after April 30. So, if you are reseeding a CWRS on May 23 that was originally seeded May 3, you stand to lose 16% of your CWRS yield. For barley, that yield loss would jump to 26%. This is due to decreased moisture availability, less solar radiation captured through the season, increased heat during flowering time, and increased risk of insect pressure. Malt barley seeded later is also at higher risk of being rejected due to quality issues that arise from late seedings such as late tillers, harvest challenges, and lack of uniform seed production. These factors can all lead to reduced malting quality.

If the assessment of the frost-injured crop indicates a low plant stand, it is also important to consider the distribution of the damage. Likely, frost damage will not occur uniformly across the field. Rather, the damage will be present in areas that are more prone to frost damage (this will vary due to the various factors listed in the above introduction). Therefore, one must assess the percentage of the field that has very low plant stands compared to areas that still have an acceptable number of plants per square foot. If the damaged area is only a small percentage of the field, it may be best to manage that area differently rather than implement a full reseeding management plan.

In summary, if the average plant stand for a wheat or barley crop is below 100 seeds/m2 (9.3 seeds/ft2) after a frost event, it is recommended to bring out an experienced agronomist to assess reseeding decisions. Before any reseeding decisions are made, producers should contact their crop insurance provider, consider yield loss associated with a late seeded crop as well as assess fertilizer, volunteer, and pesticide decisions required for a new crop.

Crop coverage information for AFSC can be found here.

Establishment information for Saskatchewan Crop Insurance can be found here.

Information on annual crop insurance from Manitoba Agricultural Services Corporation can be found here.

References

Chen, C., Neill, K., Wichman, D., and Westcott, M. 2008. Hard red spring wheat response to row spacing, seeding rate, and nitrogen. Agronomy Journal 100(5): 1296-1302.

Collier, G.R.S., Spaner, D.M., Graf, R.J., Beres, B.L. 2021. Optimal agronomics increase grain yield and grain yield stability of ultra-early wheat seeding systems. Agronomy. 11, 240. https://doi.org/10.3390/agronomy11020240

Forbes, J.C. and Watson, R.D. 1992. Plants in Agriculture. Cambridge University Press. 355 pp.

McKenzie, R.H., A.B. Middleton, and E. Bremer. 2005. Fertilization, seeding date, and seeding rate for malting barley yield and quality in southern Alberta. Can. J. Plant Sci. 85(3):603-614.

McKenzie, R.H., Bremer, E., Middleton, A.B., Pfiffner, P.G., and Woods, S.A. 2011. Optimum seeding date and rate for irrigated cereal and oilseed crops in southern Alberta. Can. J. Plant Sci. 91(2) 293-303.

O’Donovan, J. T., Turkington, T. K., Edney, M. J., Juskiw, P. E., McKenzie, R. H., Harker, K. N., Clayton, G. W., Lafond, G. P., Grant, C. A., Brandt, S., Johnson, E. N., May, W. E. and Smith, E. 2012. Effect of seeding date and seeding rate on malting barley production in western Canada. Can. J. Plant Sci. 92: 321330.

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In general, the main concern with seeding into dry soils is emergence. Lack of, or variable moisture, can lead to uneven emergence. Uneven emergence leads to variable crop development throughout the field, lower yield potential, more weed issues, less than ideal timed in-crop management, and harvest challenges leading to lower quality grain. This article will address minimizing the potential of variable crop germination and emergence.

It should be noted that bumper crops are no less likely when seeding into dry soils as compared to seeding into moist soils (assuming even emergence). After consistent germination and emergence, it is the rainfall and available soil moisture during the rest of the plant's growth that will impact the final yield. Therefore, the main goal of seeding into dry soils is to provide the best opportunity for even germination.

There are three scenarios to approach seeding wheat and barley into dry soils.

• Scenario 1: Seed at normal depth (1-2”) into dry soils and wait for rain
• Scenario 2: Seed deep (>2”) to reach soil moisture
• Scenario 3: Wait for the rain, then seed at normal depth

Scenario 3 is typically the least desirable. Although waiting for rain can help ensure that you have a greater chance of seeding into moisture, there are risks involved with waiting. First, when rain does arrive, it may continue to rain and delay seeding or limit field access and passability. The next risk is yield reduction due to delayed seeding. Research by Mckenzie et al. ( 2011) compared seeding dates of various crops including CWRS wheat, durum, SWS wheat, CPS wheat, feed barley, triticale, malt barley, barley silage, canola, and flax. Research indicated a downward trend of 0.6 to 1.7 percent yield loss per day after April 30th. This yield loss is due to less solar radiation being received by the crop, increased soil moisture availability, increased tillering, decreased disease pressure, and reduced maximum temperatures.

Additionally, O'Donovan et al. (2012) indicated that delayed seeding of malt barley can reduce kernel plump while increasing protein. Finally, Collier et al. (2021) indicated that seeding CWRS wheat at 2-6°C provided the greatest yield and yield stability when combined with high seeding rates and dual seed treatments. Therefore, having the seed already in the soil when rain does occur allows the crop to emerge earlier than if seeding is delayed until after rain has already occurred.

Scenario 1 and 2 are the more common approaches to seeding in dry conditions. Deciding between the two requires careful consideration of current soil moisture depth. Although recent research on seeding depth is few and far between, there are some assumptions we can make. These assumptions are that deeper seeded cereals require more energy and time to emerge. This presents a few problems. First, increased risk of the seed running out of energy or reaching the soil surface with low energy reserves. This increases the risk of seed and seedling death. Additionally, there is an increased chance of disease or pests killing or otherwise negatively affecting the seeds before emergence. Duzek and Piening (1982) investigated the effects of deep seeding vs intermediate vs shallow seeding in spring barley. In most years, deeper sown seed lots proved to yield less. However, in drier years, deeper sown seed yielded higher. Earlier emergence of the deeper sown seed lots due to moisture access was the likely cause of higher yields. However, the higher amounts of tillage used in this study likely increased the depth that soil moisture could be found. This demonstrates the relationship between seeding depth and emergence timing. Gan and Stobbe (1995) also looked at varying seed depths on the emergence and yield of spring wheat. Their results indicated that the highest yields were found at shallow seeding depths. One can anticipate a reduced level of crop competition with weeds if emergence is delayed (Lafond and Harker, 2011). Knowing that delayed emergence can arise from seeding shallow in dry soil or from seeding too deep, addressing current soil moisture is a vital step before seeding. If targeting deeper seeding, using increased seeding rates and seed treatment is recommended. This will be especially important in fields that do not have extended rotations. Fields with short rotation are more likely to harbour seeding diseases that will impact emergence.

As mentioned above, uniform and even germination are important when we discuss crop establishment. When we are seeding into soil that is dry on the top couple of inches and moisture can be found below, there is a high likelihood of variable moisture through the top of the soil profile. For example, depth to moist soil may be 2-3" in low areas and 3-4" on knolls. There is no optimum seeding depth and emergence will be uneven. The remaining seeds will be stranded in dry soil. If this occurs, crop maturity will vary across the field. Attempting to place all of the seed into moisture may result in very deep seeding and some seedlings never emerging. Conversely, if the seed is sown shallow (1.5-2") but above the level of soil moisture, when rains do occur, it is more likely the rainfall will evenly wet the soil to depth. Although germination may be delayed while waiting for rainfall, the seed is more likely to germinate and emerge evenly across the field.

It would be valuable for producers to walk some of their fields to determine soil moisture depth and variability of depth. Those fields that have moisture only below 2" may be better off seeding shallow and waiting for rain rather than seeding deep and risking variable germination. For fields that have a consistent moisture line between 1.5-2" may benefit from seeding closer to 2" if each seed is expected to be placed into moisture.

One question that needs to be considered when seeding into dry soils is “How much moisture is required to achieve germination?” Although germination of wheat and barley can occur at 35-40 per cent of field capacity (FC), 50 per cent FC is more likely to achieve even germination. A soil’s FC is the maximum amount of water a soil can hold. Different textured soils hold different quantities of water before reaching FC. Taking time to walk fields to assess soil moisture can provide an indication of soil moisture at different depths across the field. Using a soil probe, collect soil and different depths and locations. The number of sample locations will vary based on field variability. Eight to 12 sample locations provide a good idea of field variability. Fields with higher variability may require more sample locations. After collecting a sample, use the visual hand-feel method to determine per cent FC. A guide on implementing the visual hand-feel method to determine per cent FC can be found here. The information collected can then be used to help determine the appropriate seeding depth.

Additional considerations to mitigate risk when seeding into dry soils:

• Seeding rates
• Split nitrogen applications
• Fertilizer seed safety
• Seed treatments
• Herbicide carryover
• Pre-emergence herbicides

Seeding and mortality rates
Seeding into dry conditions adds stress to the germinating seed. Therefore, higher mortality rates may be expected. We can combat this by increasing seeding rates and expected mortality in our seeding rate calculation. Targeting higher seeding rates provides yield benefits for both wheat (Beres et al.,2011, Beres et al., 2020, Collier et al., 2021, and Isidro-Sanchez et al., 2017) and barley (O'Donovan et al., 2012 and Perrott et al., 2018). To help maintain target plant stands, increase your seeding rates to minimize the risk of a low population plant stand.

Split nitrogen applications
One option producers can implement when seeding into dry conditions is reduced nitrogen (N) rates at the time of seeding. Applying 60-70% of normal N and planning to follow up with an in-crop application can reduce the risk of nitrogen going unused in a dry year. However, considerations around equipment, available labour, and timing of an in-crop N application around rainfall all need to be considered. If an in-crop nitrogen application cannot be completed, and rainfall returns to more normal levels, yields will be lower due to limited nitrogen availability.

Fertilizer Seed Safety
Recommended maximum nitrogen rates in the seed row are based on good soil moisture (75% of FC). However, if seedbed moisture is poor (less than 50% of FC), seed placed nitrogen should be reduced by 50% from the recommended rate. Applying rates above this will increase the risk of seed death due to fertilizer injury. For information on your N seed safety rates, locate your provincial recommendations. Alberta recommendations can be found here in Table 4. Saskatchewan recommendations can be found here on page 1. Manitoba recommendations can be found here.

Seed Treatment
As mentioned previously, seeding into dry conditions or seeding deeper will increase the risk of seed and seedling mortality. To reduce mortality risk, dual (fungicide + insecticide) seed treatments can be used. Dual seed treatments that include both an insecticide and a fungicide have been shown to increase the abiotic resistance of seedlings (Beres et al., 2016 and Larsen and Falk., 2013). This means that a seed treated with a dual fungicide will have a greater chance of surviving dry or deep seeding conditions.

Herbicide Carryover and Pre-emergence Herbicides
Although not directly related to seeding, herbicide carryover and the use of pre-emergence herbicides must be considered. For herbicide carryover, many crops are vulnerable to Group 2, 4, and 27 herbicides. When considering whether herbicide carryover is a risk on your farm, look at the in-season rainfall after herbicide application time into September. Once soil temperatures drop in the fall, little herbicide breakdown occurs. Herbicide breakdown requires adequate soil moisture, temperature, and time. Breakdown occurs via soil microbes which require ample time under adequate soil moisture and temperature conditions. Herbicide carryover injuries may not show up until after a soaking rainfall event, which releases the herbicide from soil particles and washes it into the rooting zone. If rainfall after the use of herbicides in these groups is less than 150 mm, one can expect some risk of herbicide damage. More information on herbicide carryover risk by area, in Saskatchewan, can be found here.

Pre-emergence herbicide use has been on the rise for the past decade. This is due to several factors including implementing multiple modes of action on-farm to combat herbicide resistance. However, some pre-emergence herbicides require 'working' the product into the soil through some form of tillage such as heavy harrows. When soil conditions are already dry, incorporation of pre-emergence herbicides through tillage (even light tillage) will further reduce the soil moisture. Additionally, breaking up already dry soil may lead to increased wind erosion of the soil as well as increased risk of seedling damage from blowing soil particles.

Information on herbicide carryover risk in Manitoba can be found here while information from Saskatchewan can be found here.

Summary
Seeding into dry soil conditions creates added challenges and risks to the already complex process of seeding. However, taking the time to assess soil moisture can help to make the best decisions to increase the chances of an evenly germinated crop. Additionally, assessing the benefits of adjusted seeding rates, fertility rates, fertilizer seed safety, and seed treatments can provide some added measures to reduce risks for the seed and seedlings.

References
Beres, Brian L., et al. "Integrating spring wheat sowing density with variety selection to manage wheat stem sawfly." Agronomy Journal 103.6 (2011): 1755-1764.

Beres, Brian L., et al. "A Systematic Review of Durum Wheat: Enhancing Production Systems by Exploring Genotype, Environment, and Management (G× E× M) Synergies." Frontiers in Plant Science 11 (2020): 1665.

Beres, Brian L., et al. "Winter wheat cropping system response to seed treatments, seed size, and sowing density." Agronomy Journal 108.3 (2016): 1101-1111.

Collier, G.R.S.; Spaner, D.M.; Graf, R.J.; Beres, B.L. Optimal Agronomics Increase Grain Yield and Grain Yield Stability of Ultra-Early Wheat Seeding Systems. Agronomy 2021, 11, 240.

Duczek, L. J., and L. J. Piening. "Effect of seeding depth, seeding date and seed size on common root rot of spring barley." Canadian Journal of Plant Science 62.4 (1982): 885-891.

Gan, Y., and E. H. Stobbe. "Effect of variations in seed size and planting depth on emergence, infertile plants, and grain yield of spring wheat." Canadian Journal of Plant Science 75.3 (1995): 565-570.

Lafond G., and Harker N. “Seeding Rate and Seeding Depth”. Agriculture and Agri-Food Canada. Presentation.

Isidro-Sánchez, Julio, et al. "Effects of seeding rate on durum crop production and physiological responses." Agronomy Journal 109.5 (2017): 1981-1990.

McKenzie, R. H., et al. "Optimum seeding date and rate for irrigated cereal and oilseed crops in southern Alberta." Canadian Journal of Plant Science 91.2 (2011): 293-303.

Larsen, R. James, and Duane E. Falk. "Effects of a seed treatment with a neonicotinoid insecticide on germination and freezing tolerance of spring wheat seedlings." Canadian Journal of Plant Science 93.3 (2013): 535-540.

O’Donovan, J. T., Turkington, T. K., Edney, M. J., Juskiw, P. E., McKenzie, R. H., Harker, K. N., Clayton, G. W., Lafond, G. P., Grant, C. A., Brandt, S., Johnson, E. N., May, W. E. and Smith, E. 2012. Effect of seeding date and seeding rate on malting barley production in Western Canada. Can. J. Plant Sci. 92: 321330.

Perrott, L. A., et al. "Advanced agronomic practices to maximize feed barley yield, quality, and standability in Alberta, Canada. I. Responses to plant density, a plant growth regulator, and foliar fungicides." Agronomy Journal 110.4 (2018): 1447-1457.