Montana Wheat Production Guide

The intent of this publication is to provide current information on wheat production for producers within the state of Montana. The authors have attempted to provide all the basic information necessary for the establishment and management of a wheat crop. More detailed information can be found on certain topics by following the links to the referenced websites. Many of the references in this publication are available through MSU Extension Publications, as well as through your local county Extension office.

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Cereal Grain Development Scales

Cereal Grain Development

Modified from www.extension.umn.edu/agriculture/small-grains/growth-and-development/spring-wheat/index.html

Editor

Kent A. McVay, associate professor and Extension cropping systems specialist, Department of Research Centers, Montana State University, located at the Southern Agricultural Research Center, Huntley, MT.

Contributing Authors

All authors are faculty members of Montana State University. Kent McVay is the principle author, assisted by Clain Jones, associate professor and Extension nutrient management specialist in the Department of Land Resources and Environmental Sciences; Mary Burrows, professor and Extension plant pathology specialist in the Department of Plant Sciences and Plant Pathology; Fabian Menalled, professor and cropland weed specialist in the Department of Land Resources and Environmental Sciences; and Kevin Wanner, associate professor and Extension entomology specialist in the Department of Plant Sciences and Plant Pathology.

Acknowledgments

The authors would like to thank the reviewers that helped to make this a more inclusive and complete publication. Thanks to Marko Manoukian, Darren Crawford, Kathrin Olson, and Ryan Buetow for technical and editorial review.

Layout and design by MSU Extension Publications.

Disclaimer

Common chemical and trade names are used in this publication for clarity of the reader. Inclusion of a common chemical or trade name does not imply endorsement of that particular product or brand and exclusion does not imply non-approval.

Introduction

Between five and six million acres of wheat are harvested annually in Montana, representing an annual market value greater than $1 billion (Anonymous). For the years 2007-2016, approximately 48% of this acreage was spring wheat, 42% winter wheat, and 10% durum. Durum acres have been steady at a half million acres for the past decade while spring wheat acreage has fluctuated from 2.5 to nearly 3 million, trading acreage mostly with winter wheat. Recent trends show spring wheat acreage approaching that of winter wheat by 2016. During this same period pulse acreage in Montana has grown from 300 thousand to over 1 million acres with little impact on total wheat acreage. The increase in pulse acreage has likely come from a decline in fallow practices but also includes some acreage from the Conservation Reserve Program (CRP) as contracts expire. Interestingly reduction of fallow has not reduced winter wheat yields. On the contrary, yields have increased an average of 0.4 bu/year over this same time period.

This production guide is designed to help both new and experienced growers and agricultural consultants find science-based answers when time is short and a management decision must be made. The goal of this publication is to provide those answers and connect you to relevant sources for wheat production information.

Growth and Development

Wheat (Triticum aestivum L.) is an annual grass with both winter hardy and spring cultivars. Winter wheat generally has greater yield potential than spring wheat, especially when moisture is adequate. Yields reported by National Agricultural Statistics Service (Anonymous) for the past 10 years (2007-2016) indicate Montana spring wheat averaged 29 bu/acre while winter wheat averaged 40 bu/acre. As a general rule, in any given year spring wheat yield will be about two-thirds that of winter wheat.

In Montana, winter wheat is more likely to be grown following fallow than spring wheat. For some regions of the state like the northeast, winter kill of winter wheat can be a significant limitation. A large acreage of durum wheat (Triticum durum Desf.) is produced in Northeast Montana where breeding efforts, industry support, and sufficient summer rains favor this crop.

It is important to understand growth and development of the wheat plant in order to correctly use fertilizers, plant growth regulators, and pesticides for crop production. Many pesticide labels restrict application to when the crop is at certain growth stages referred to as either Feekes or Zadoks growth scales (see front inside cover of this publication). Applications of nutrients, herbicides, plant growth regulators, fungicides, and irrigation water should be based on the stage of crop development rather than calendar dates. Poor timing of these operations can reduce effectiveness or result in crop injury and yield loss. Crop growth rates will vary depending on variety, planting date, and growing conditions, including nutrient and water availability.

Variety Selection

One of the most important management decisions a producer makes is the choice of variety. Variety trial information is compiled each year from trials conducted near each of the Research Centers in Montana. This data is available in several formats but one of the easiest ways to find data is through the Variety Selection tool on the Southern Agricultural Research Center website (www.sarc.montana.edu/php/varieties/). Results for the past 10 years are available in a format that gives the user control. By choosing locations, and years, the results displayed will be an average over your inputs. For example if you want to see one year’s data, select a location and year and that data is retrieved. The displayed results can then be resorted by yield, test weight, or protein to help compare varieties. To average two locations, just select both locations for a particular year and then the data is recalculated and displayed. In this way you can build average results for multiple locations over multiple years. This is exactly how you should evaluate a variety. Select a variety that performs well over multiple trials in space and time. Yield may be most important, but protein and test weight are important as well. Disease and insect resistance or tolerance are important characteristics that should also be compared. By selecting the variety name on this web tool, a written description with further information on disease resistance and characteristics such as solid stems will be retrieved. By choosing multiple varieties with disease resistance and other defensive traits, risk can be spread in case of pest outbreaks.

Across the state, but especially in Montana’s Golden Triangle region, spring wheat is very susceptible to sawfly damage. Where sawfly pressure is high our current best management recommendation is to grow a solid-stem or semi-solid stem variety of wheat to provide some resistance to damage. This and other information on specific varieties can be found in the annual “Performance Evaluation and Recommendations” publication located on the MSU Plant Sciences and Plant Pathology (PSPP) website (plantsciences. montana.edu/crops/index.html). The latest evaluations of varieties under sawfly pressure are presented in table form and can be found within the written variety descriptions.

Winter kill of winter wheat can be a concern for many producers. Winter survival and associated yields are evaluated each year in the Sidney and Williston, ND, areas. Data is presented in the Annual Performance Evaluation and Recommendation publication found on the PSPP website. Use this information to help you decide on the right variety for your operation.

Several herbicides are labeled for control of downy and Japanese brome in winter wheat. These herbicides have specified conditions for use to ensure winter wheat tolerance and effective control of the annual bromes. Another option for brome and grassy weed control is the use of ‘Clearfield’ wheat, varieties which are specifically bred for tolerance to the herbicide Beyond (imazamox). Beyond will control downy brome and other select weeds. Check the label. Clearfield crops should not be grown more than 2 in 4 years as per the Beyond label. This restriction is designed to reduce the risk of developing herbicide-resistant weeds to Beyond by rotating chemical modes of action and reducing selection pressure.

New varieties are released each year. Yield levels have steadily increased over time, end use qualities have improved, while pest resistances have been broadened through efforts of breeders. Periodically check how the variety you grow performs as compared to the latest new releases. Evaluate new varieties that are available and look for a variety that shows greater yield potential or has the specific disease or insect-resistant package you need to address current challenges. If the variety you plant is more than five years old, there is likely a new variety that is better adapted, higher yielding or of higher quality.

Seeding Dates and Rates

Winter wheat should be planted early in the fall as to have four to six weeks of growth prior to dormancy. This provides ample time for plants to establish a root system, a crown, and a number of tillers. Tillers that form during the fall produce most of their growth in the spring. Planting too early can result in rank growth in the fall, increase the potential for the infestation by diseases which are spread through a “green bridge” (see Plant Disease section, beginning page 10), and risk depleting the soil of water which can leave the crop susceptible to winter kill. Planting too late can result in small plants with few tillers and shallow root systems that may also be at risk of winter kill. Row spacing of winter wheat has not been found to be critical between 4” and 12” for grain yield in the Northern Great Plains (Lafond and Gan, 1999). Closer rows tend to crowd out weeds and provide slightly higher plant populations likely due to less inter-seedling competition. But, wider rows in no-till tend to perform better since less movement of surface residue occurs when seeding is required.

For dryland winter wheat, a planting rate of 40 to 60 lb/ acre (15 to 21 seeds/ft2) of pure live seed (PLS) is usually sufficient to establish the crop. In high residue no-till systems, increasing the rate to 60 to 80 lb/acre (21 to 28 seeds/ft2) PLS is recommended to compensate for some poorly placed seeds that won’t establish. Seeding rate should be increased if seeding is delayed to compensate for the likelihood of reduced tillering. As a rule, don’t drill into a green (weedy) seedbed. First either spray or till the field prior to planting so that the seedbed is weed-free. Try to plant into moisture. Seeds should be placed at least 1 inch below the surface, but if moisture is deeper, set the drill to place seeds up to 3 inches deep. It’s best to plant into moisture to get the crop established on time rather than to drill into dry soil and be dependent on subsequent precipitation to establish the crop. If time is running out in the fall, wheat can be successfully dusted in and will establish after moisture is received. A good management practice by most producers is to first wait for and then spray a flush of winter annual grasses like downy brome or cheatgrass prior to planting winter wheat.

Spring wheat should be planted when average soil temperature at 2 inches exceeds 40°F. Planting earlier can delay germination resulting in weaker, less vigorous plants. If a pre-plant herbicide has been applied, for example a triallate, delayed emergence can increase seedling mortality from herbicide poisoning. Both spring and winter wheat will continue to grow into the summer season as long as soil moisture is available and maximum daily air temperatures remain below the 90s°F. For this reason, delayed planting of spring wheat typically results in reduced yields because of a shortened grain-filling period.

Wheat seeding rates

Desired populations when planted on time. Increase seeding rate if planting is delayed.

Crop	Plants/acre x 1,000,000	Plants /ft2
Dryland winter wheat	0.7 – 0.9	15 -21
Dryland spring wheat	1.0 – 1.2	22 - 28
All irrigated wheat and durum	1.3 – 1.4	30 - 32

For unusually large or small seed, correcting for seed density (seeds/lb) is a good practice. Use the following formula:

Seed Rate (lbs/a) = Desired plants/a / Seeds/lb x %Germ x %Stand 

Example: Assume your seed has a density of 17,500 seeds/lb.

The germination is 98% and you expect to establish 90% of what you plant.

Seed Rate (lbs/a) = 1,000,000 / 17,500 x 0.98 x 0.90 = 64 lb/acre

Soil temperature is affected not only by air temperatures, but also by residue levels. In tilled or fallow soils where much of the residue has decomposed, soils will warm more quickly in the spring than where high levels of residue remain. Previous crops of peas or lentils produce less residue which will largely decompose by the following spring. These conditions allow soils to absorb solar energy and warm more quickly as compared to fields with high levels of residue.

If planted on time for your region, dryland seeding rates for spring wheat should be 60 lb/acre PLS (21 seeds/ft²). If spring wheat planting is delayed, the seeding rate can be incrementally increased up to 90 lb/acre (30 seeds/ ft²). Spring wheat tillers less than winter wheat so plant a high enough population to optimize yield potential. Irrigated spring and winter wheat should be seeded at 90 to 100 lb/acre (30 to 34 seeds/ft²). Row spacing of spring wheat has not been shown to influence grain yield in the range of 6 to 12 inches for dryland production, but tighter rows for irrigated systems is recommended because of the higher plant populations.

Seeds should be placed at 1 to 2 inches below the soil surface into good soil moisture. Shallow planted seed typically emerges quicker. A minimum planting depth of 1 inch will ensure that the crown of the plant develops and remains below the soil surface.

Recent research in Alberta, Canada (Beres et al., 2011), indicates an interaction of wheat stem sawfly (WSS) with plant populations of spring wheat or durum. The solid-stemmed cultivar Lillian generally had optimized grain yield and high and stable pith at seeding rates of 23 to 33 seeds/ft². A higher seed density for hollow-stemmed treatment was warranted based on the findings that WSS infestation rates decreased and parasitism of WSS increased at higher seeding rates. For wheat produced in regions prone to WSS infestation the authors encourage seeding rates of ≤ 28 seeds/ft² for solid-stemmed cultivars and increased seeding rates of 37 to 42 seeds/ft² for hollow-stemmed varieties.

Cropping Systems

FALLOW SYSTEMS

The 2012 Ag Census indicated 25% of Montana’s over 12 million crop producing acres were fallowed. This amount is down from 29% in 2007 and includes land planted to cover crops that were not harvested. In the early 20th century, the practice of fallowing land was widely adopted across the Great Plains to reduce the risk of crop failure in dry years. Fallow cropping is most successful where soils are deep. Soil texture is also important. For example, a silt loam soil can hold 10 inches of available water in a 5 foot profile (depth). Plants extract water from wherever they establish roots. A deep silt loam soil, once charged with water, provides a great safety net for crops like winter wheat which can establish roots to 5 feet. But spring and durum wheat only produce roots to a depth of about 4 feet. That limits their access to the soil water reservoir. Because of their texture, lighter sandy soils hold less water and thus store less water. Shallow soils are also restricted in how much water they can store because of the lack of soil depth. For example, a 3 foot sandy soil over a cobbly subsoil may only retain 4 to 5 inches of available water. Fields with restrictions in soil water storage like this are not good candidates for fallow systems. They provide a poor safety net of soil water storage for crop production in dry years.

It is important to keep the soil weed-free during the fallow period as weeds use water. Herbicides such as glyphosate are typically used during the fallow period. To help prevent the development of glyphosate resistant weeds, tank mixing of products with other modes of action for use during the fallow period is recommended. Tillage can be used but is not as effective in retaining moisture as chem-fallow systems. Crop residue on the surface reduces soil evaporation, helps cap- ture precipitation by preventing soil crusting and sealing, and mulches the soil surface, all which helps to retain moisture.

Precipitation storage efficiency (see Box below) varies through the year and the existing soil water status. During the summer, when evaporation potential is highest, PSE is typically lower than during the fall and winter. In fact PSE can actually be negative, which means more water is lost than is gained through precipitation. This occurs regularly during the summer following the crop year as shown in Figure 1, page 4 (Nielsen, Unger, and Miller, 2005).

Designing cropping systems to minimize fallow during the low efficiency period of May through September is one way to improve water use efficiency. In a wheat-fallow system 51% of the non-crop period occurs during the highly efficient fallow period directly following harvest while a significant 31% occurs in the summer when fallow efficiency is low. By using a more intense rotation of wheat–corn–proso millet, Colorado researchers were able to shift the periods of fallow or non-crop time so that 79% of the fallow was in the highly efficient storage period directly following a crop while only 5% remained in the low-efficient period. This practice improved precipitation storage efficiency, which in return improved profitability.

Precipitation Storage Efficiency (PSE)

Definition: the amount of water stored in the soil as a percentage of the total amount of precipitation received.

Example: Assume your field receives 12 inches of precipitation over the course of one year. If soil moisture is determined at the beginning of this period, and again at the end, the total amount of water stored can be calculated. Assume we can account for an increase of 9 inches of soil moisture.

PSE = 9/12 X 100

         = 75%

FIGURE 1. Precipitation storage efficiency in three time intervals in the fallow period of a wheat-fallow system in NE Colorado.

In Montana, it’s difficult to successfully grow warm-season grasses like corn and millet in dryland production systems, but there are cool-season crop options that may be used to improve water use efficiency. For example, alternating wheat with pulse crops such as peas or lentils in continuous crop production can make better use of stored moisture from the fall and winter non-crop period following wheat harvest. Pulses are shallow rooted, using moisture only from the upper 2-3 feet of soil. They grow quickly and mature early as compared to wheat, providing a short but highly efficient fallow period following harvest. Late summer and fall rains can recharge the surface soil for fall or spring planting while deep moisture is retained for the crop that can be used the following year.

With the advent of no-till production systems, the need for fallow has been lessened. It is no longer necessary to perform tillage operations prior to planting to prepare a seedbed. Most modern-day equipment can plant through high levels of residue. And when the land is continuously cropped, yields and the accompanying residue are more manageable as compared to the high level of residue that can occur in a wheat-fallow system. In fact when a producer makes the move from fallow systems to continuous cropping, rather than working the soil to reduce residue levels, management to maintain residue on the soil surface to help retain precipitation becomes one key to success.

TILLAGE

Wheat can be successfully produced under any tillage system. As no-till and reduced-till systems have become the norm for Montana dryland wheat production, the questions have changed from “Will using no-till reduce my yield?” to “Will an occasional tillage operation hurt or improve my wheat yield?” The benefits of reduced-till systems include: lower labor and fuel costs, reduced soil erosion and loss from wind and rain, less labor or time in the field, and more efficient use of stored soil moisture. The trade-off is a greater need for herbicide use, greater potential for disease or insect damage and more expensive planting equipment.

In most instances the benefits of no-till systems outweigh the costs. Comparing overall herbicide programs of no-till and conventional-till systems reveals that the difference in expenses for a no-till system occurs primarily during the fallow period. Within-crop herbicide use is likely to be similar across tillage systems. The risk of greater disease or insect pressure in a no-till system can be offset by adopting appropriate crop rotations and by choosing varieties with better disease and insect resistance. When it is time to replace a grain drill, consider choosing equipment that provides greater flexibility. Some soil conservation districts have no-till drills available to try, which gives producers hands-on experience. A no-till seeder can achieve good stands in diverse and difficult seedbeds and many have the added benefit of delivering fertilizer in bands separate from the seed row. Successful no-till begins with harvest and residue management. It’s important to evenly distribute straw and chaff across the width of the harvested swath. Adding straw choppers to the combine helps to distribute straw and accelerate residue break down. An alternate option is to use a stripper header that strips the grain from the head without cutting the straw. This eliminates the need for redistribution and does the best job of maintaining an even distribution of residue in the field.

In irrigated cereal grain production, the levels of straw associated with high yields requires management to prepare the field for the next crop. Options include tillage, baling, or burning the straw. Annual burning of straw is not considered a sustainable practice as soil organic matter content will decline under sustained burning. Using short-statured, semi- dwarf varieties can help reduce total tonnage of residue. Tillage is common especially in flood-irrigated systems where water flow and uniform water distribution is critical to production of the next crop.

As found in dryland systems, there are benefits to not tilling the soil in irrigated systems. The challenges to irrigation in a no-tillage system are residue and water management. But even if straw is removed, enough disease organisms in the remaining residue or soil will survive to potentially infect the next crop. So crop rotation is even more important in a no-tillage irrigated system. Grain drills and planters must be of no-tillage quality to cut through residue and correctly place the seed. Greater success can be found by u