Agronomics of Winter Cereal Production

David Struthers, Executive Manager

Winter Cereals Canada Inc.

Introduction:

Much of the current interest and success with direct seeding can be attributed to the learning experiences producers had with no-till winter wheat during the 1980's. In Saskatchewan, during the 1980's, the acreage of direct seeded winter wheat was greater than the total combined direct seeded acreage of all other annual commercial crops. Winter cereals are "systems" crops that have an excellent fit in direct seeding and zero tillage production systems. As more producers in Western Canada adopt these systems, the opportunity to successfully produce winter cereals will grow. However, to achieve this success producers must become familiar with the agronomic management practices that have been developed specifically for these crops.

Why Grow Winter Cereals?

Some producers have been reluctant to include a winter cereal in their rotation. The reasons commonly cited for not growing winter cereals include concerns about additional labour and equipment requirements at seeding time, the time conflict associated with seeding a winter cereal during the harvest of spring crops, and grain handling and storage concerns. All of these factors are management related and can be overcome with good planning. Producers who have learned to adapt their cropping systems to include winter cereals have noted the following benefits:

• Increased economic returns through higher crop yields and lower crop input costs
• More efficient use of spring soil moisture and precipitation
• Farm work load and labour requirements are spread more evenly throughout the year
• More efficient use of capital investments (equipment, etc.)
• Numerous potential end uses (grazing, green feed, silage, and grain) that help to diversify risk and provide greater flexibility
• Improved weed control and the opportunity for reduced pesticide use
• Soil, water and wildlife habitat conservation

Other agronomic advantages offered by these crops have also contributed to the renewed interest in winter cereal production. The earlier development and maturity of winter crops tends to reduce the risk of certain insect and disease infestations such as Orange wheat blossom midge and Fusarium head blight (scab). In the spring, the competitive advantage winter cereals have over weeds often provides an opportunity for producers to eliminate the use of grassy weed herbicides. This makes winter cereals an excellent tool for managing herbicide rotations and reducing the risk of weed resistance.

The Keys to Success!

The production of winter cereals is straightforward but requires different management practices than those used for spring seeded cereals. Much has been learned about successful winter cereal production over the past two decades. Dr. Brian Fowler, the winter wheat breeder at the University of Saskatchewan's Crop Development Centre, has devoted considerable time and effort into understanding and promoting the "best management practices" for winter cereal production in western Canada. His research and observations have been compiled into the Winter Wheat Production Manual, a comprehensive how-to guide for winter cereal growers.

1. Pre-planning

There is no substitute for good planning. Many of the winter wheat failures of the past can be attributed to poor management practices that resulted from poor planning and decision making. Successful winter cereal growers all have one thing in common - they plan ahead! The winter season, prior to planting of spring crops, is the time to gain more knowledge and start thinking about your winter cereal crops. There are a number of considerations:

1. Field selection - The physical characteristics and previous management history of the field that you plan to seed can have an impact on the success of the crop. Is the topography suitable? Is drainage adequate or is the field prone to flooding? What is the field history in terms of weeds, insects, diseases, etc? Are there soil factors that may limit the potential for winter cereals?
2. Selection of the spring crop - You want to have suitable stubble available for seeding by late August or early September so you need to consider the seeding date, days to maturity and management of your spring crop. Will it be harvested in time to fall seed your winter cereal? Will the chosen spring crop provide adequate standing stubble to support snow trapping? Are you planning to use a pre-emergence or post-emergence herbicide that will leave a soil residue?
3. Sourcing seed and fertilizer - It is a good idea to have your seed and fertilizer arrangements made by early summer, well ahead of fall planting time. Winter cereal seeding often occurs during breaks in the harvesting of spring crops. Having the seed and fertilizer ready on the farm means that you can make more efficient use of your time.
4. Equipment and labour arrangements - Seeding and harvest are the two busiest operations during the year. It is critical to plan the logistics of equipment and labour. Who will spray the field prior to seeding? Who will do the seeding? Is the seeding equipment field ready? What equipment is available in terms of tractors and trucks for seed and fertilizer? What about bin space?
5. Managing spring crop residues - Winter cereals, particularly winter wheat and winter triticale, require standing stubble that is capable of trapping snow to insulate the overwintering crown tissue. The spring crop should be cut as high as possible and the straw and chaff should be spread thoroughly to prevent seeding problems. Erect, dense stubble is the most effective. It is important to plan field traffic routes during harvest so that stubble knockdown is minimized. The snow trapping potential (STP) for any type of stubble can be easily calculated using the following formula:

STP = stubble height (cm) x stubble stems per m²

100

An STP index greater than 20 is acceptable for winter wheat and winter triticale. Values below 20 indicate a higher risk of winter injury. Fields with a lower STP are better suited for fall rye due to its winter hardiness. Cereal stubble such as barley or oats often have an STP index of 90 or greater, while canola stubble is often in the 25 - 30 range.

1. Variety Selection

2. There are several registered cultivars of winter cereals available. Provincial variety guides should be consulted since each variety has its own agronomic characteristics and regional adaptation.

   Winter wheat	Fall rye	Winter triticale
   AC Bellatrix	AC Remington	Bobcat
   AC Readymade	AC Rifle	OAC Wintri
   AC Tempest	Danko	Pika
   CDC Clair	Dakota
   CDC Falcon	Musketeer
   CDC Harrier	Prima
   CDC Kestrel
   CDC Osprey
   CDC Raptor

3. Winter Survival

4. Winter cereals overwinter as seedlings. In order to survive winter conditions, they must acclimate or "harden off". Soil temperatures at the depth of the crown tissue regulate the genetic system that induces cold acclimation. Cold acclimation begins in the fall once soil temperatures drop below 9^o C. Once this process starts, the degree of cold hardiness, and the maintenance of low temperature tolerance, are directly related to the sequence of temperature changes that plants are exposed to during the fall and winter. In other words, cold acclimation can be stopped, reversed or restarted by changes in temperature!

   

   Schematic of a winter cereal plant showing the development of the over-wintering crown tissue

   Soil temperatures gradually decrease as winter approaches. Four to eight weeks at crown temperatures below 9^o C is usually required to fully harden plants. Under normal circumstances, full cold acclimation is achieved by early December. At this point, the crown tissue can withstand short-term exposure to temperatures in the range of - 22^o C (Figure 1). Winter hardiness gradually decreases over the winter in order to allow the plants to "deharden" and resume growth in the spring. This process is also governed by temperature. Producers are often too hasty in deciding that slow growth in the spring indicates that the crop has suffered winter injury. In most instances, provided that proper agronomic practices were used, the crop has survived and the plants just need a few days of warm temperatures to resume growth.

   

   Figure 1. Changes in cold hardiness for the period from September to May

5. Seeding Methods

Research has shown that winter cereals are most successful when grown in a direct seeding or zero tillage production system. These systems provide the snow trapping potential that is required to insulate the plants from harsh winter weather and enhance spring soil moisture conditions. Many different types of seeding equipment can be used as long as they are capable of seeding shallow, at a consistent depth, with minimal stubble disturbance.

1. Seeding Date - In order for winter cereals to achieve maximum cold tolerance, healthy, vigorous plants must be established before freeze-up. A plant that has three or four true leaves and is starting to develop its first tiller would be ideal. By this stage, crown tissue has developed just below the soil surface. It is the crown tissue that survives the winter and regenerates roots and leaves in the spring when favourable growing conditions return.

2. Fall soil temperatures influence optimal seeding dates. As a result, the optimal timing for seeding differs in each production region of western Canada. Research has demonstrated that seeding during the period from late August to early September (approx. August 25^th to September 5^th) consistently produces the best crops in terms of both yield and quality. It is always better to seed early rather than late as late seeding often results in reduced winter hardiness (Figure 2).

   

   Figure 2. Influence of seeding date on winter hardiness of winter wheat

   The stage of plant development prior to winter freeze-up also impacts the agronomic performance of the crop during the following growing season. Seeding too early often results in yield reduction and smaller seed size. Late seeding results in significant yield reduction, delayed heading, later maturity, lower bushel weights and increased problems with weeds and other crop pests such as insects and disease organisms.

   All this being said, there are several uncontrollable factors that impact the crop's potential. This includes soil temperature, soil moisture and weather conditions the following growing season. Responses to seeding date cannot always be determined simply by looking at a calendar!

3. Seeding Depth - Under optimal conditions, winter cereals should be seeded less than 1" deep into a firm, moist seedbed. Deeper seeding delays emergence and results in weak, spindly plants that are more susceptible to winter injury. Research indicates that improper seed placement usually results in later maturity and reduced yield potential.

1. Fertility Management

As with all other crops, the fertility requirements for winter cereals should be based on a reliable soil test, used in conjunction with knowledge of past management practices and local cropping conditions. It must be noted that winter cereals have the potential to out-yield their spring counterparts by 20 to 25%. To achieve the higher yield potential, winter cereals require higher rates of fertilizer than spring cereals, particularly nitrogen. It has been suggested that insufficient nitrogen fertilization is the leading cause of lower than expected yields of winter cereals relative to spring types.

Nitrogen - Nitrogen is necessary for photosynthesis and is the major component of both yield and grain protein. Winter cereals demonstrate strong responses to applied nitrogen due to their higher yield potential and the fact they are seeded into standing stubble fields that tend to be low in residual soil nitrogen. The traditional practice for winter cereals has been to broadcast 34-0-0 early in the spring. However, with the development of new direct seeding implements and openers, producers are looking at a number of alternatives for nitrogen.

Research data shows that the most consistent response in terms of both yield and quality is from spring broadcasting of 34-0-0. Urea (46-0-0) and urea ammonium nitrate (28-0-0) are subject to losses in the spring through volatilization, reducing the efficiency of application by as much as 10 - 20% depending on soil moisture and rainfall. Sidebanding all the nitrogen requirements at seeding is becoming more popular with the development of double shoot sidebanding openers. However, producers should be aware that the risk of fall leaching losses is high under this scenario. Conversion of applied nitrogen to nitrate is a factor due to the warm soil temperatures that prevail in late August and early September. If sufficient conversion takes place the nitrate will be subject to leaching.

Current research is demonstrating that the yield response of winter wheat to applied nitrogen is optimized at approximately 11.5% grain protein. The crop will utilize applied nitrogen to satisfy yield first - protein will only surpass 11.5% once the crop's yield requirements have been met. This response is also dependent on growing conditions, especially soil moisture and precipitation. Depending on market opportunities and protein premiums, there may be situations where nitrogen fertility can be managed to increase grain protein and improve economic returns.

In the big picture, the form of nitrogen used is secondary to timing, placement and rate. The important points to remember with nitrogen fertilization are:

• Get lots on - Winter cereals have a higher yield potential, thus a greater requirement for nitrogen. Rates should be 20 - 25% higher than those used for spring cereals.
• Get it on early - Winter cereals require nitrogen very early in the spring. Broadcasting or surface banding should begin as soon as the field will support the weight of equipment (i.e. mid April). Over 90% of the total nitrogen accumulated in a winter wheat plant is taken up early heading, which normally occurs in mid to late June. If you delay broadcasting until the spring crop is seeded, winter cereal yields will suffer. Successful growers fertilize early in the day when there is still enough frost to support their equipment.

• Observe the same precautions as spring cereal with respect to seed placement of nitrogen. Germination injury and increased risk of winter injury can result from high rates of seedplaced N. Row spacing, opener design and seedbed utilization are important considerations.

P, K and S

These nutrients are essential for successful winter cereal production. Phosphorus enhances winter survival by promoting early plant development as well as vigorous root and shoot growth. The phosphate requirements should be seedplaced or sidebanded at seeding time. Research indicates that phosphorus deficiencies have an impact on winter hardiness (Figure 3). Winter wheat seeded into soils with low residual phosphate levels that do not receive sufficient seedplaced phosphorus can be subject to significant reductions in winter hardiness. The risk of winter injury increases, and adequate insulation from snow cover becomes more critical.

Figure 3. Impact of seed placed phosphorus on winter hardiness

Potassium chloride (KCl) helps plants tolerate moisture stress conditions and improves lodging resistance. The chloride component has been linked to lower incidence of certain foliar and root diseases. Sulphur is often required on winter cereals, particularly in incidences where the crop is sown on canola stubble. Sulphur helps to increase the efficiency of nitrogen and phosphorus applications and plays an important role in end use parameters such as flour yield and loaf volume. Application rates for phosphorus, potassium and sulphur should be based on soil test recommendations.

Micronutrients

Growers throughout Alberta have noted responses to applications of micronutrients, particularly copper. Soil texture, pH and interactions with other nutrients can significantly impact on the availability of these nutrients. Micronutrient fertility must be planned in conjunction with N, P, K and S to ensure the proper balance of nutrition is maintained. Growers who are optimizing their use of macronutrients, particularly nitrogen, are more likely to see responses to micronutrients, even in situations where there is no known micronutrient deficiency. It is advisable to conduct soil tests and plant tissue analyses to determine the potential responses from micronutrient applications.

6. Disease Management

Winter cereals are susceptible to many of the same disease problems found in spring cereals. This includes root, leaf and stem diseases as well as flowering diseases such as fusarium head blight. However, due to the earlier maturity advantage, winter cereals tend to be less affected by certain pathogens. Fields should be monitored carefully in conjunction with growing conditions to estimate infection levels and the cost-effectiveness of fungicide application. Fungicides such as Tilt and Dithane are registered for use on winter wheat.

Summary

The production of winter cereals is straightforward but requires different management practices and a different thought process than spring cereals. Growers who have made the transition are successfully capitalizing on the many agronomic, economic and conservation benefits offered by these diverse crops.