Issue 78
Prairie Grains





Prairie Grains is the official publication of the Minnesota Association of Wheat Growers, North Dakota Grain Growers Association, Montana Grain Growers Association and South Dakota Wheat, Inc.

Copyright Prairie Grains Magazine
Summer 2006

Crop Development

Relative Maturity of Field Crops
Following is average days to physiological maturity of many crops grown in the Northern Plains. Early killing frost plus extreme high temperatures at flowering stages are the two factors most limiting yields of late planted crops.  Time required for maturity varies with variety or hybrid, seeding date, geographic region, and available growing degree days. A shortage of growing degree days can increase days required for maturity. Corn, soybean, sunflower and millet are especially sensitive.

Seeding to Physiological Maturity or Swathing Stage (days)









Proso millet




Field Pea






Dry Bean






Corn (Grain)




Things You Might Not Know About Wheat Development

  • After seedling emergence, leaves are produced at a rate of about one every 4 to 5 days.  A total of 8 or 9 leaves are usually produced.  The last leaf is the flag leaf, which emerges after at least three nodes are present above the soil surface.
  • At the three leaf stage, tiller production begins in earnest and shortly thereafter the growing point on the main stem switches from forming new leaves to forming the spike.
  • It is during the very short period between the three leaf and six leaf stages that the number of spikelets per spike are fixed. Most physiologists agree that the short period of active spike development is probably the single most critical phase in determining grain yield potential.
  • Under usual field conditions, a plant may produce a total of three tillers in addition to the main shoot, although not all will necessarily produce grain. Tillers that appear at the time that the 4th, 5th, and 6th leaves emerge on the main shoot are most likely to complete development and form grain. Tillers formed later are likely to abort without producing grain.
  • The peduncle, the last elongated internode which supports the head, accounts for a good proportion of the overall stem length.
  • The “boot” stage is just prior to head emergence, when the flag leaf sheaf (or collar) encloses the growing head. Stress during this stage of development can cause tiller death. Florets per spike is the yield component most affected by stress at this stage.
  • Within a few days after heading, flowering (pollination) begins in the head, starting first with the florets in the central spikelets. The period of pollination within a single head is about four days. Post-flowering stress can cause floret abortion and reduction in grain weight. Wheat is extremely sensitive to heat during flowering.
  • Most of the final kernel weight is accumulated one to two weeks after pollination, during the “soft dough” stage, when kernels accumulate starch and protein rapidly and dry weight increases. 


Wheat Growth Stages
All grain plants follow the same general pattern of development, although the specific time interval between stages, the number of leaves and nodes on the main stem and the number of tillers will vary by variety, season, planting date and location. As well, the amount of growth for any variety is directly related to nutrient and moisture availability.

Still, the rate of growth development for any wheat variety is directly related to temperature (accumulated heat units), except under extremely dry conditions. Thus, by knowing the planting date for wheat, and by tracking weather data, one can predict growth development and plant stage. This helps growers make timely treatments to control weeds, topdress fertilizer, control diseases, and other management decisions.

(The 2006 Hard Red Spring and Durum Wheat Management Calendar is in the hardcopy of Issue #78. Please call 1-800-242-6118 to receive a copy.)  The North Dakota Agricultural Weather Network (NDAWN) can help growers keep track of weather and growing degree days. On NDAWN’s Internet home page ( ) click on the “applications” link. There, you will find a number of applications for using NDAWN, including:

  • Predicting Sclerotinia risk in canola
  • Corn degree days
  • Potato late blight severity
  • Sugarbeet degree days, growth stages, cercospora
  • Sunflower degree days
  • Wheat degree days, growth stages, disease forecasting, midge forecasting
  • Crop water use
  • Insect degree days
  • Heating/cooling degree days

Consult with an agronomist, certified crop adviser, or county extension agent/educator for more background on growing staging crops, or about how to apply NDAWN information. NDSU has a publication online, “Identifying Leaf Stages in Small Grains,” at  The University of Minnesota publication “Growth and Development Guide for Spring Wheat” can be found online at

Soybean Growth Stages
The following divides soybean plant development into vegetative (V) and reproductive (R ) stages. With the exception of the first two stages, the (V) stages are designated numerically as V1, V2, V3, etc. through V(n) where (n) represents the number for the last node stage of a specific variety. The (n) will fluctuate with variety and environmental differences. The eight R stages are simply designated numerically.

The V stages following VC are numbered according to the uppermost fully developed leaf node. Start with the unifoliolate leaf node when counting the number of fully developed leaf nodes. A leaf node is fully developed when the leaf above it has leaflets which are fully unrolled. That is, the leaflet edges are no longer touching.

Vegetative Stages
Stage  Description






Unifoliolate and first trifoliolate leaves are fully developed


Unifoliolate and first two trifoliolate leaves are fully developed


Unifoliolate and first three trifoliolate leaves are fully developed

 (n) Unifoliolate and (n) trifoliolate leaves are fully developed

Reproductive Stages
Stage  Description


Open flower at any node on the main stem


Open flower at one of the two uppermost nodes on the main stem with a fully developed leaf


Pod is 3/16 inch long at one of the four uppermost nodes on the main stem with a fully developed leaf


Pod is 3/4 inch long at one of the four uppermost nodes on the main stem with a fully developed leaf


Seed is 1/8 inch long in the pod at one of the four uppermost nodes on the main stem with a fully developed leaf


Pod containing a green seed that fills the pod cavity at one of the four uppermost nodes on the main stem with a fully developed leaf


One normal pod on the main stem that has reached its mature pod color


95% of the pods have reached their mature pod color

Sources: Iowa State University, Purdue

Bloom Key Soybean Development Stage
The beginning bloom stage or R1 stage in soybeans is marked by the plants having at least one flower on any node of the main stem. If there is still a need to spray for weeds, check the label carefully for spraying after flowering begins. There are a number of herbicides that can be used after flowering begins. Always read and follow label guidelines when using pesticides.

Soybeans are at 50% bloom when an open flower can be found on every other plant in a row. Flowering, unlike maturity on soybeans, begins toward the bottom of the plant (at the third to sixth node) and then progresses upward and back downward. Branches off of the main stem will flower a few days later than the main stem. While flowering begins at the base of the plant and proceeds to the top of the plant, physiological maturity of the beans will progress anywhere on the plant stem.

Normally, soybean pods will be mature in the middle or top of the plant and down. Thus, remember to check pods toward the bottom of the plant when determining if harvest time has come.

Flowering of soybeans is an important time in bean growth and development. At stage R2, full bloom, each plant has accumulated about 25% of its total dry weight and nutrients; it has attained about 50% of its mature height; and, it has produced 50% of its total mature node number.

This later flowering stage begins the period of very rapid N-P-K and dry matter accumulation that will continue through R6. Also, during flowering, the soybean plant gears up on its nitrogen fixation in order to provide for the demands of the plant. Scout for disease and insect problems (aphids) during this critical early time period of flowering.


Soybean Maturity 101
Dates of maturity are listed in variety performance tables and indicate when the plants in a variety are observed and estimated to be physiologically mature. Usually harvest will commence approximately 7 to 14 days after the soybeans are physiological mature.

Relative maturity ratings consist of a number for the maturity group designation such as: (000-early, 00- mid early, 0-mid or 1-late) and followed by a decimal and another number, ranging from .0 to .9, which indicates maturity rankings within each maturity group. Each 0.1 change in group rating represents approximately 0.75 to 1 day later maturity.

For example, the variety ‘Jim’ is indicated as 00.6, making it a medium maturing variety in the 00 group. ‘Walsh’ would be a 0.0, making it one of the earliest varieties in the 0 group whereas ‘Sargent’ is a 0.8 making it one of the later varieties in the 0 group. Few if any group 1 soybeans are currently planted in N.D. except in the extreme southeast part of the state.

Check Your Soybeans for Nodulation
Soybean plants that are five to six inches tall should have their first unfolded leaflets (V2 stage). Nodulation, the symbiotic relationship of bacteria on the soybean roots, can be seen shortly after emergence, but the plant is not actively fixing nitrogen until the V2 to V3 stages. The number and nodules formed on the soybean roots along with the amount of nitrogen fixed increases until the R5.5 stage. Nodules actively fixing nitrogen for the plant are pink or red inside. White, brown or green nodules indicate that nitrogen-fixation is not occurring. Nitrogen fertilization after planting (other than pop-up or early, limited fertilization) is not recommended as nitrogen fertilizer applied to active nodules will render these nodules inactive or inefficient, depending on the amount of nitrogen applied. Soil nitrogen is utilized over fixed nitrogen, if available in large amounts.

Check the health of your soybean nodules and check root proliferation (both of which may be a concern in continuous beans). Soybean roots should be dug up to check nodules and not pulled from the soil. The pulling action tends to slough off nodules and results in an inaccurate assessment. At V2, soybeans should be rooting down six inches into the soil and by V5 will completely reach between 30-inch rows, making any cultivation at V5 needing to be very shallow.

Percent of Yield Produced By Various Soybean Growth Stages

Growth Stage Yield

Days After Bloom Begins

Days to Maturity

Percent of Total

Begin pod




Full pod




Begin seed




Full seed




Begin maturity




Full maturity




Source: University of MN

Soybean Stand Compensation and Yields
Soybeans have the remarkable ability to compensate for reduced stands through aggressive branching. University of Minnesota research suggests that even substantial reductions in plant stands has negligible impact on yield. The data below from the National Hail Insurance Services handbook supports this research. As the table indicates, reduced soybean stands can produce acceptable yields. However, weed control management may need to be closely watched. Incomplete canopy closure can create additional weed pressures.

Soybean Stand Reduction Loss

Row Width








Plant Count


Yield % Optimum














































NOTE: All plant counts are made on the basis of “number of plant in 10 feet of row.”

Corn Growth Stages
The following divides corn plant development into vegetative (V) and reproductive (R) stages. The (V) stages are designated numerically as V1, V2, V3, etc. through V(n) where (n) represents the number of leaves with visible collars. The first and last (V) stages are designated as VE (emergence) and VT (tasseling). The six reproductive stages are simply designated numerically.

Each leaf stage is defined according to the uppermost leaf whose leaf collar is visible. Loss of the lower leaves will begin about V6 due to increased stalk size and nodal root growth. To determine the proper leaf stage after lower leaf loss, split the stalk lengthwise and inspect for internode elongation. The first node above the first elongated internode is generally the fifth leaf node. This fifth leaf node can be used as a reference point for counting the top leaf collar.

Vegetative Stages
Stage  Description




One leaf with collar visible


Two leaves with collars visible


(n) leaves with collars visible


Last branch of tassel is completely visible

Reproductive Stages
Stage  Description


Silking - silks visible outside the husks


Blister - kernels are white and resemble a blister in shape


Milk - kernels are yellow on the outside with a milky inner fluid


Dough - milky inner fluid thickens to a pasty consistency


Dent - nearly all kernels are denting


Physiological maturity – the black abscission layer has formed

Sources: Iowa State University, Purdue

Corn Growth Staging
The growth and development of corn is largely regulated by temperature accumulations and not calendar days. In fact, corn development can accurately be predicted from corn growing degree day accumulations. Corn growing degree days are calculated using a base temperature of 50 degrees and can readily be obtained from the NDAWN web site ( by going to “corn degree days” under the “applications” section on the left hand section of the home page.


At the five leaf stage, the corn plant switches from vegetative growth to reproductive growth as the growing point stops initiating leaves and begins initiating the tassel. At the 6 leaf stage, ear shoots begin to form. The number of kernel rows on the developing ear is determined relatively soon after it begins development and is largely determined by genetics, and less so by the environment. The length of the kernel row and therefore the total number of potential kernels, however, is determined during a longer period of time (6 leaf stage through one to two weeks before tasseling). Severe stress during this stage can shorten the length of the cob and reduce yield potential. Nevertheless, stress during ear development is far less damaging to yield potential than stress during and shortly after pollination, as the potential number of kernels developed typically exceeds the number that can be pollinated filled.

Certain management practices are growth stage dependent; therefore, properly identifying the growth stage of your corn crop will be important to ensuring that management practices are applied at the appropriate time. This is particularly true of the application of herbicides. When growth staging a crop you should begin by obtaining a representative sample of plants from the field or part of the field of interest. Remove any soil attached to the plants so that you are able to observe the roots and crown.

Vegetative growth stages of corn are defined by the number of leaves. Counting leaves in corn is fairly straight forward as the process is not encumbered with tillers and leaves on tillers as is the case in small grains. However, care must be taken to ensure that the earliest leaves are included when counting leaf numbers. The first leaf is small and often dies and is torn from the plant early in the growth of the plant. The first leaf has a blunt tip. Look for sheath remnants at the crown of the plant if you suspect that the first leaf (or second for that matter) is missing. Include only those leaves that have a collar. Include all leaves, even those that have been damaged by hail or frost. The total number of leaves that a plant will develop is more or less fixed for a given hybrid; leaves that are stripped from the plant will not be replaced by additional new leaves.

In order to determine the growth stage of older plants that have lost their lower leaves, uproot the plant and split the stem with a knife through the root ball. At the very base of the stem, identify the first visible internode. Internodes are the white area between the more yellow bands of the nodes. The first obviously visible internode should about ½ to 3/4 inch in length. The node directly above this internode will be the fifth node, and the leaf arising from this node will be the 5th leaf. Find that leaf and continuing counting leaves from that point.

In corn, management recommendations can also refer to the height of the plant, rather than leaf stage. For example, certain herbicides can only be applied to corn less than 12 inches tall. The plant height in this case is measure from the base of the plant to where the upper most leaf reaches without stretching it out.

Canola Growth Stages
Determining the growth stages of canola is relatively simple using a scale developed in Canada. This scale uses five principal stage designations and subdivides these into secondary stages. These stages are described in the following growth chart. With herbicide tolerant canola, one has to pay special attention to plant stage for last application. For Roundup Ready canola, application can be made from seedling emergence to bolting (5 - 6 leaf). For Liberty Resistant canola, the application can be made from seedling stage up until early bolting stage (3.2). For Clearfield canola varieties, Beyond application can be made up to just prior to bloom.

Canola in the 5.3 to early 5.4 stage should be near or at swathing stage. These stages change very rapidly during the ripening period if temperatures are warm and under dry conditions.


Description of Canola Growth




Seedling - cotyledons showing


2.1 First true leaf expanded
2.2 Second true leaf expanded
2.3 Etc. for each additional leaf


Bud (Bolting)
3.1 Flower cluster visible at center of rosette
3.2 Flower cluster raised above level of rosette
3.3 Lower buds yellowing


4.1 First flower open
4.2 Many flowers opened, lower pods elongating
4.3 Lower pods starting to fill
4.4 Flowering complete, seed enlarging in lower pods


5.1 Seeds in lower pods full size, translucent
5.2 Seeds in lower pods green
5.3 Seeds in lower pods green-brown or green-yellow, mottled yellow
5.4 Seeds in lower pods yellow or brown
5.5 Seeds in all pods brown, plant dead

How Saturated Soil Affects Cereal Crop Growth
Waterlogging (ponding/saturated soils) affects a number of biological processes in plants and soils, and can be damaging to crop growth. The primary cause of damage to cereal crops by waterlogging is oxygen deprivation. The rate of oxygen depletion in a saturated soil is dependant on a number of factors, but temperature is the most important and predictable factor; the higher the temperature the faster the rate of oxygen depletion. Generally, the oxygen level in a saturated soil reaches the point that is harmful to plant growth after about 48 to 96 hours.

Effects on corn - The growing point of the corn plant remains below the surface of the soil until the 5-6 leaf stage and is quite sensitive to waterlogged conditions at this stage. Young corn plants can be killed if soils are saturated beyond 48 hours, particularly when soil temperatures are high (i.e. above 65F). Waterlogging also reduces root growth and predisposes the plant to root rots later in the season. To determine if plants have been killed by ponding, wait 3 to 5 days after the excessive moisture has drained through the soil and then check to see if there is any visible re-growth.

Effects on small grains - Barley is reported to be more sensitive to temporary waterlogging than is wheat. Furthermore, varieties vary considerably in their response to waterlogging.  Sensitivity to waterlogging generally decreases as crops mature, with spike size and tiller numbers being the yield components most affected. Though leaf yellowing is common in small grains after soils have been waterlogged, yield loss can occur, even if these visible symptoms are not observed.

Effects on the soil - Waterlogging can also indirectly impact cereal crop growth by affecting the availability of nitrogen in the soil and by reducing root development. Excessive water can cause leaching of nitrate nitrogen beyond the rooting zone of the developing plant, particularly in lighter textured soils. Furthermore, when oxygen levels become depleted, nitrate nitrogen is converted to a gaseous form that is lost to the air. Research conducted in other states has found losses between 1 and 5% of the nitrate N lost for each day that the soil remains saturated.

Corn responds to additions of N when N is limiting up to the beginning of grain filling. Consider sidedressing N to corn fields with good stands where excess water may have caused problems. In small grains, in order to impact yield, additional N should be applied prior to the 6 leaf stage. Additional N applied after this stage would be more likely to impact wheat protein levels rather than yield.

Sunflower Development, Growing Degree Days
The following growing degree days formula uses 44F as the base temperature and 86F as the maximum for calculation. High and low temperatures are used each day to obtain a cumulative number of GDD’s. See table for approximate growth stages of sunflower as related to relative heat units.

Sunflower Stage

Plant Description

GDD* units




4 True Leaves
8 True Leaves
12 True Leaves
16 True Leaves
20 True Leaves
Miniature Terminal
Bud <1.0” from leaf
Bud >1.0” from leaf
Bud open Ray flowers visible
Early flower (Start Pollination)
50% flowered (50% pollinated)
Flowering Complete
Back of head - pale yellow
Bracts green - head back yellow
Bracts yellow - head back brown



*Average number of Days and GDD units accumulated from planting

Source: NDSU Carrington Research Extension Center: 2 yrs. Data average over five sunflower hybrids

Check the NDSU NDAWN web site for the 2006 Growing Degree Units in various locations in N.D. ( Just enter in the planting date and the current date for your location.

Evaluating Herbicide Injury
When evaluating crops involved in suspected herbicide injury, keep in mind that some other factors may have caused the observed effects or the herbicide may be only one of a combination of several casual factors. Look for other possible causes. Are there holes in the leaves or stems or pruned roots from insect damage? Weather and soil conditions that cause plant stress may make the crop more susceptible to herbicide injury – has there been severe weather such as wind, drought, hail, flooding, frost, or high/low temperatures that could have caused damage or compounded the diagnosis? Could a disease be involved? Could it be excessive or misplaced row fertilizer or a nutrient deficiency? Or is the effect resulting from a combination of causes?

Look for patterns of injury in the field. Herbicide injury is often in a pattern associated with soil types or movement of application or incorporation equipment. Observe other susceptible crops or weeds in the area for herbicide effects. For comparison, try to find a check area where no herbicide was applied in the same field.

If you conclude that herbicides are the probable cause of crop injury, try to determine why the injury occurred. Limited crop tolerance to certain herbicides is sometimes a problem, especially under heavy rainfall or sandy soils or on dry, loose soil. Misuse of high rates, wrong chemical, contaminated spray tank, improper method of application, nonuniform application, overlaps, improper applicator adjustments and tillage operations that concentrate the chemical are some causes of herbicide injury. Some varieties/hybrids are more susceptible than others.

Don’t be too hasty to evaluate the effects of herbicide injury. Give the plants a chance to recover. Check growing points to see if the plants have potential for recovery. Compare injury effects and weed control benefits. Stand counts and injured plant counts are important considerations. Consider digital photos of initial symptoms and to help gauge plant damage and possible recovery. Unbiased yield checks later in affected and unaffected similar areas of the same field are the best estimates in damage losses.

Diagnosing plant problems
Local agronomists and county extension agents/educators are an excellent resource for diagnosis; the following plant labs can also help diagnose plant pests and problems. Contact the lab for instructions before submitting plant samples.

IPM Surveys Track Growing Season Field Pests
Crop scouting results from North Dakota field surveys are posted on the NDSU IPM web page at:  This site provides maps and updates indicating weekly survey results for diseases and insect pests of various field crops. Links to additional information about these pests and other IPM (integrated pest management) resources are provided as well. The Minnesota Department of Agriculture Plant Pest Survey and Crop Pest Fact Sheets can be found online at – a wealth of timely pest information – what’s happening where – can be found during the growing season here as well.

NDSU – Waldron Hall, Room 206, PO Box 5012, Fargo, ND, 58105, ph 701.231.7854, email: , web site: . Fee-based services include insect, weed, disease identification and control recommendations, herbicide injury diagnosis, and soybean cyst nematode screening.

UM - Plant Disease Clinic, St. Paul, ph. 612.625.1275. Web site: www.extension.umn .edu/distribution/cropsystems/DC3170.html.  Fee-based services include plant disease, virus ID, nematode analysis, as well as seed quality testing.

SDSU – Oscar E. Olson Biochemistry Labs, Brookings, ph 605.688.6172, web site: SDSU Plant Disease Clinic: (click on Plant Disease Clinic). Ph 605.688.5157

Link to more private and public testing labs can be found online:

These labs (as well as professional crop consultants/certified crop advisers) can help determine key factors that affect crop productivity, such as:

Soil organic matter tests – Knowledge of the organic matter level will serve as a guide in selecting an effective herbicide and rate of application, as well as helping to assure crop safety. Testing once every five years should be adequate.

Herbicide spray water analysis – High salt levels in spray water can reduce weed control in nearly all situations. Calcium, and to a lesser degree, magnesium, are antagonistic to 2,4 -D and MCPA amine , dicamba, and glyphosate.

Plant tissue analysis – This indicates the nutrient status of plants at the time of sampling, serving as a monitoring tool for determining the adequacy of current fertilization practices. Plant tissue analysis will also detect unseen nutrient deficiencies and may confirm visual symptoms of deficiencies. Toxic levels also may be detected. Combined with soil test information, a plant analysis report can help a producer tailor fertilization practices to specific soil-plant needs.