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ISSUE 2   May 13, 1999


    With nearly 70% of corn farmers applying strictly post herbicides to their fields, recommendations
and timing of applications must be on target. This narrows the application window, especially for corn,
as corn can be hurt by early weed competition. It is better to spread your risk by using both a pre-emerge
and a post-emerge weed control program. However, a strong, early post program may be the make it
or break it input.

    The shorter season and unusual weather patterns seen in North Dakota and Central and Northern
Minnesota, require that post_only programs be well thought out. Optimizing a post program requires
prior knowledge of the weed spectrum expected out in the field, applications that don't let weeds
compete too long with young crops (moderate weed pressure can hurt corn yields if weeds get taller
than 4") and built-in prevention on some of the fields to guard against weather or timing delays is

    Post applications provide the advantage of allowing the producer to match the chemical treatment
to the weeds in a field. And, the wide array of post products make a post-only system very attractive.
Knowing the weed history of a field can narrow down the chemical choices, and the label limitations
on some of the post products narrows the field more-depending on spray timing differences and the
spread of each farmer's workload across his farm. Cost differences may also help you make up your
mind. Herbicide persistence and hybrid limitations with certain chemicals will also make the decision
more apparent.

    One of the best ways to plan your post program is to map out the expected weed pressure in each
field. In other words, first determine whether you are going after primarily broadleaf weeds; moderate
grass and broadleaf pressure; heavy broadleaf and grass pressure; or, primarily grass weeds. Then,
map out alternatives for each scenario represented on your farm on each field.

    For primarily broadleaf weeds, first determine what weeds are the problem. If the weed early on
the scene is primarily lambsquarters, your window of opportunity to spray can be narrowed and your
herbicide selections can be specific for this early weed species. Short residual activity will work on
weeds that emerge early and don't have sporadic, alternative emergence timings throughout the season.
Atrazine and oil, Aim, Basis, Basis Gold, Distinct, Scorpion III, Sencor and Tough all do a good job
of controlling lambsquarters. Canada thistle, a perennial, also emerges early. Accent Gold, Curtail,
Distinct, Hornet and Stinger will provide control, especially on younger plants. Check recommendations
on the broadleaves you want to control and see how the controls have worked and what the prices are
in your area.

    With a mix of broadleaves, look for approved combinations that work. For general annual broadleaf
control in corn, Shotgun has been used up until the 3_leaf stage or Buctril (in warm conditions, not cool,
wet conditions) plus a little atrazine at the 5-6 leaf stage can be applied if the season is running a little
later. In areas where high pH soils don't present a problem with rotations from residual atrazine,
Marksman has been applied. But, if 2,4-D and brittle corn stalk visions have you worried or the use
of atrazine within your rotation on high pH soils cause alarm, look for other alternatives that work in
your area. You may just need a Sencor application to provide broadleaf control in your field.

    On fields with moderate grass and broadleaf pressure, key in on what weed species are the main
problems, which produce the most seed (and consequently will add more to the field's weed seed bank),
which might be easily controlled with light tillage if you are not going no-till and then select a chemical
combination which works well on the key weed seed producers that aren't easily controlled by
cultivation. For instance, Basis Gold and Clarity applied up until the 5-leaf stage on hybrids (88_day
or above hybrid maturity) work well to control most annual grasses (and quackgrass, a perennial) as
well as many broadleaf weeds.

    Fields with heavy broadleaf and grass pressure require more effort and decision-making. You may see
a need for use of Liberty Link or Roundup Ready hybrids to simplify the weed control if hybrids are
available in the maturity group you plant. Otherwise, shop around for the best combinations which
control your key weed culprits and be prepared to spend more money on control and scouting until
you get your weed seed bank down to more manageable weeds and weed populations.

Work your fields for the long haul by considering long_term benefits in controlling the weeds in each
field. Know the weeds present in order to match the chemicals to the weed array in each field and
the hybrids planted. Timing of application is critical. Don't let weeds compete too long with corn.
Recognize the limitations to the application windows on the chemicals you want to use.
Consider alternatives if weather or late season problems prevent use of some herbicides.

Denise McWilliams
Extension Agronomist



    The North Dakota Soybean Growers Association and North Dakota Soybean Council are again
sponsoring a yield contest in 1999. Most rules of the contest are similar as in the past. Divisions and
geographic boundaries will be the same as last year. The state has been divided into four growing
regions, plus a separate youth division, irrigation division and a no-till division. Both adults and youth
can enter and compete in the contest. Youth must be members of 4-H or FFA.

    Agribusiness firms such as elevators, seed companies, implement and chemical dealers, banks,
chambers of commerce, etc., can pay entry fees and/or furnish products to individual contestants
for use in the contest.

    Only (1) entry per individual ownership, partnership, or corporation is allowed.

    Winners in each division will be awarded prizes. Final results and awards will be announced and
presented to winners at a special awards program next winter at the ND Soybean Expo on February 10, 2000.

    September 5th is the entry deadline. A fee of $25 per adult entry and $15 per youth entry will need
to accompany all applications. Inquiries or entry forms can be obtained from:

North Dakota Soybean Growers
1351 Page Drive Suite 103
Fargo, ND 58103
Telephone number: (701) 239-7194



    What is the optimum seeding rate for flax? The recommended seeding rate for flax is 30 to
50 pounds per acre
. Flax is not competitive with weeds at all stages of development. Seeding rate
trials at Langdon and Minot indicated that higher yields were obtained with higher seeding
. The higher seeding rates of 40 to 60 pounds per acre also established more plants, which is
very important with weed competition. The yield of the higher seeding rates at Langdon were reduced
where lodging occurred. A flax stand of 70 plants per square foot is desired. However, if uniform stands
of 30 to 40 plants per square foot exists, a satisfactory yield can occur.

Seeding Rate

Langdon, ND

Minot, ND




------------------Yield bu/A------------------























    Late planting in some flooded areas or replanting decisions can be somewhat based on plant growing
or development days required for various crops. Below is listed the average days to physiological
maturity of many crops grown in North Dakota. 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. Relative maturities for major crop hybrids
and varieties are listed in the respective NDSU variety performance circulars.

Seeding to Physiological Maturity or Swathing Stage (days)












Dry bean




Proso millet


















Field pea



Duane R. Berglund
Extension Agronomist




    Demonstrating some patience now will be a key if producers want to avoid potential problems
later in the growing season. Waiting until the soil has dried sufficiently before working will result in
more favorable seedbed conditions maximizing plant stands and final yields.

    Tillage of wet soils for seedbed preparation can result in excessive clod formation, poor seed soil
contact, an uneven and dried-out seedbed, poor mixing and incorporation of chemicals, uneven erratic
seedling emergence, and reduced plant stands. Don’t be in a big hurry to work wet fields. Patience is
the best recommendation when fields are wet. Waiting 1 to 2 additional days usually will not lengthen
the growing season, but will greatly aid in obtaining a good seedbed for planting and to maximize
plant stands.

    When planting in compacted wet conditions the seed is put in an anaerobic environment. When
seed germinates in an anaerobic environment, the lack of oxygen generally results in the death of the
germ. Seeds that do survive will be weak and the wet soil conditions may be more favorable for the
development of soil borne pathogens that otherwise may not be a problem. The end result is reduced
stands and lower yields

    Germination of wheat or barley in compacted conditions will hinder coleoptilar growth, preventing
shoot development and soil penetration of the radicle, retarding root development. In addition, any
crusting that occurs will further prevent the coleoptile from emerging resulting in seedling loss. The end
result of both is an erratic and reduced stand. Uneven crop stands typically yield lower than uniform
stands due to direct competition of plants at different stages of growth growing next to one another.



    In North Dakota planting small grains after May 15 typically results in a 1.5 to 0.5% per day
reduction in yield. The reduced yield is a result of fewer tillers and smaller heads. Some compensation
can be made with increased seeding rates.

    Yield potential in small grains is a function of three components head number, kernel number per
head and the weight of each kernel. As any one of these components is increased or decreased
yield changes accordingly. Heads produced per unit area is directly related to seeding rate, or crop
stand, and tillering during early vegetative development.

    Yield reduction due to late planting is a result of longer days and the increased probability for
high, potentially detrimental temperatures during the 3 to 6 leaf stages. Yield potential, or head
number and kernel number is determined during this period. The long days and hot temperatures
during early vegetative development results in fewer heads per plant and spikelets per head and
a lower yield potential. The lower yield potential can be offset in part by increasing seeding rates.
A five to ten percent increase above typical seeding rates for every ten days planting is delayed
beyond May 15 should be sufficient. The recommended seeding rate for small grains in North Dakota
is 1.25 to 1.30 million plants per acre, or about 30 plants per square foot.

    Late planting generally results in higher grain protein. While high protein is a plus in wheat, high
protein barley may not make malt quality. If barley is in your crop plan, plant it first and make sure
total nitrogen does not exceed your yield goal. Nitrogen recommendations for malting barley are
1.5 lbs/acre for every bushel of expected yield, and 2.5 lbs/acre for every bushel of wheat.

Michael D. Peel
Small Grains Extension Agronomist



    Recent rains have caused flooding and ponding across low field areas. Prolonged soil saturation
affects crop growth and yield. Corn is very sensitive to flooding in the early vegetative stages
(especially prior to the fifth or sixth leaf stage). In early growth stages, corn or soybeans can survive
for only two to four days under water in anaerobic conditions. Moderate water movement can reduce
flood damage by allowing some oxygen to get to the plants, keeping them respiring and alive. Drainage
within one to two days increases the chance of survival.

    The injury extent to seedlings is determined by the plant stage of development at ponding, duration
of flooding and the air/soil temperatures. If temperatures are warm during flooding (greater than 77 F),
plants may not survive 24 hours. Cool temperatures may prolong survival. However, cold, wet
weather favors disease development. Seed treatments are effective, but limited in protection. Seedling
development slowed or delayed two to three weeks allow soil_borne pathogens a greater opportunity
to cause damage. Seed rots, seedling blight, corn smut and crazy top affect corn plant development
later even though ponding occurred earlier. Delayed soybean growth allows diseases such as Fusarium
root rot, Phytophthora rot and Pythium rot to establish and weaken or destroy seedlings. Limited hybrid
and variety resistance to these diseases and difficulty in predicting damage makes evaluation difficult.

    Carefully assess damage before deciding to replant. The National Crop Insurance Service in their
corn loss instruction booklet have shown that yield loss from early season stand reduction (up to the
10_leaf stage) can vary. With a 100% plant stand, yield loss is negligible; a 75% stand can equate to
a 10% yield loss; a 50% early corn stand is at least a 26% yield loss; and, a 25% stand will usually
result in at least a 43% yield loss if original seeding rates were reasonable and remaining stands were
healthy. In soybeans, research through various areas of the United States have shown that yields are
not affected by population reductions until stands drop below 125,000 plants per acre but yields can
be lower if large gaps are present. These skips can rapidly reduce yields in soybeans. According to
information from Purdue, two_foot skips in soybeans in 50% of each row can decrease yield 6%.
Three_foot skips in 50% of each row will drop yields 13%. Four_foot skips in 50% of each row
will decrease yield by 15% in healthy stands.

    Rotted seed or damped_off seedlings will reveal probable crop losses. Evaluate intended stand
to the damaged stand, the uniformity of the stand, the original planting date versus a replant date,
likely replant pest control and seed costs as well as projected crop prices. Weigh these costs and
price projections against replanting yield gains to evaluate crop injury and replanting gains.

    On surviving stands, remember that favorable weather for plants after ponding is important.
Cultivation, once soils are dry enough, will open and aerate surface soil and promote root growth.
Be careful working the soil. Working wet soil causes compaction that varies crop growth.

    An additional nitrogen application in corn may be necessary in fields that show signs of yellowing
or uneven growth. A late_spring test for nitrate when corn plants are six to twelve inches tall can
determine if more nitrogen is needed.

    Scout more intensively in previously ponded areas of corn and soybean fields. Maintain a good
weed control program so that crop plants are not robbed of nutrients and moisture later in the season.

Denise A. McWilliams
Extension Crop Production Specialist

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