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AgAlerts 2001 From Griggs County
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Issue # 16, September 24, 2001
The frost over the weekend has raised
questions about soybean maturity. To determine whether your soybeans are
safe from frost we must look at the stage of growth they are in to see if they
have reached physiolocial maturity.
R7 Stage is the beginning of maturity. R7
is when one normal pod on the main stem that has reached its mature pod
color, normally brown or tan, depending on the variety. Physiological
maturity of an individual soybean seed occurs when the accumulation of dry
weight ceases. This first occurs when the seed (and generally the pod)
turns yellow, or has completely lost all green color. Although not all
pods on the R7 Plant have lost their green color, the plant is essentially at
physiolocical maturity because very little additional dry weight will be
accumulated. The soybean seed at physioloical maturity is about 60 percent
moisture and contains all necessary plant parts to begin the next generation
soybean plant.
R8 Stage (full maturity). R8 is when 95% of the
pods have reached their mature pod color. Five to 10 days of drying
weather are required after R8 before the soybeans have less than 15%
moisture. Timeliness of harvest is very crucial for soybeans. Ideal
bean moisture content at harvest and for storage is 13%. Although harvest
may begin at higher moisture percentages, some drying costs will be encountered
for safe storage. In contrast, harvest delayed to less than 13% moisture
causes increased pre-harvest shatter loss, sickle-bar shatter loss, increased
number of splits and loss of test weight.
Frost Injury. Soybeans are easily damaged by
frost in the 28-32 degree F range. Temperatures of 28 F for any extended
period of time can completely kill soybean plants (stems and leaves). In
the event of a leaf killing frost when pods are still light green or yellow,
wait until the pods are mature in color before combing. Green soybeans can cause
market discounts. If the soybeans are only slightly green, there is a good
possibility that drying and storage will fade out the green.
Pods and seeds from a R7 soybean plant
(click to enlarge)
| Crop | # seeds/sp.ft.=1 unit loss/a |
| Flax | 42 seeds |
| Soybeans | 4 seeds |
| Corn | 2 kernels |
| Sunflower (oil) | 21 seeds |
| Sunflower (conf.) | 12 seeds |
| Navy Beans | 6 seeds |
| Pinto Beans | 3 seeds |
Here are a few
tips from Ken Hellevang, NDSU Extension Grain Handling Specialist.
Combine: The first step is to harvest and
handle the crop to obtain the best quality soybean prior to drying or
storage. Adjust cylinder and ground speeds to avoid cracking or splitting
and harvest losses. Consult your dealer or operator manual for their
recommended settings. Monitor for splits and cracks frequently to see if
the combine settings need to be changed.
Handling: Belt conveyors, bucket elevators, and drag or mass
conveyors provide the gentlest handling. Normal grain augers can be used if
operated slow and full, and pneumatic conveyors can be used if the air-to-grain
ratio is properly set and lines are laid out with a minimum number of very
gradual curves. To minimize damage during handling reduce drop heights, and do
not handle very cold grain. Many times damage that appears to occur during
handling was actually caused during drying and is exposed during handling.
Drying: Maximum moisture contents for safe storage of soybeans that
are aerated to keep them cool is 14 percent for storage over winter, 12 percent
for storage up to one year, and 11 percent for long-term storage. The
maximum recommended drying temperature for commercial (non-food) soybeans is
about 130 F for continuous flow dryers, 110 F for batch dryers, and 110 F when
drying seed. Avoid dryers which recirculate the soybeans while drying.
This additional handling tends to increase damage.
If seed-coat quality is important, keeping the relative
humidity of the drying air above 40 percent limits the amount of damage. At 40
percent relative humidity (RH), about 15 percent of the seed coats were damaged
in a research study. At 30 percent RH, the damaged increased to about 30
percent, and at 20 percent RH the amount of seed coat damage increased to about
50 percent. Warming air by 20 F reduces the relative humidity by half. For
example, air at 50 F and 80 percent RH will have a relative humidity of about 40
percent after being heated to 70 F.
It is best to harvest soybeans early and do natural air and
low temperature drying during October if possible. Soybeans will dry to about
13.5 percent moisture in 20 to 30 days with adequate airflow and normal October
conditions in North Dakota. In November, soybeans will only dry to about 15.5
percent moisture, and the drying time will be about twice as long due to colder
air temperatures. Adding supplemental heat to warm the air by 5 F will cause the
beans to be dried to about 11.5 percent moisture. The drying time will still be
longer than in October due to lower air temperature.
Minimum airflow rates of 1 cubic foot per minute per bushel (cfm/bu)
to dry soybeans at 16 percent moisture, or dryer, soybeans, and 1.25 cfm/bu for
up to 18 percent moisture beans are recommended. The expected drying time is
about 20 to 30 days at these airflow rates. The resistance to airflow is about
25 percent less through soybeans than it is through corn, so it is easy to
obtain these airflow rates. Static pressures will be much lower than occurs when
drying small grains, so an axial flow fan will likely deliver the most airflow
per horsepower. About 1 to 1.5 hp per 1,000 bushels of beans is required for
drying, depending on bean depth and airflow rate desired.
Soybeans should be cooled to 20 F to 30 F for winter storage.
Check the soybeans every two weeks until cooled to about 25 F and then check at
least monthly for changes that indicate storage problems.
Frost
Can Cause Forage Poisoning Concerns
Frost can cause potentially toxic compounds
that can cause problems in livestock. The most common toxicity problems
are associated with either nitrate, which is converted to nitrite in the body
after consumption, or prussic acid (cyanide) poisoning, both of which impair the
oxygen-carrying capacity of the blood.
Prussic Acid: Prussic acid poisoning is mainly
confined to sudangrass and forage sorghum, which both contain high levels of
compounds that can release cyanide under certain situations. Sorghums and sorghum-sudangrass
hybrids both contain more prussic acid that sudangrass. There are selected
varieties, such as Piper and Trudan sudangrass, that tend to be lower in prussic
acid. Freezing or trampling that could cause new growth, cyanide
concentration and release is increased. New leaves and shoots contain from
two to 25 times more prussic acid than stems, so new growth following a frost,
should be considered suspect.
New growth should be at least 18-20 inches for sudangrass and
24-30 inches for sorghum-sudangrass hybrids before re-grazing. If no
re-growth occurs, wait five to six days before returning cattle. If you
just plan to hay these forages, 75% while curing, so well-cured hay is rarely
hazardous for livestock.
Nitrate Poisoning: Plants more likely to
accumulate nitrates, including pigweed, lambsquarter, kochia, wild sunflower,
Russian thistle, oats, barley, millet, corn, sorghum and sudangrass.
Grasses such as brome grass and legumes such as alfalfa are not normally high in
nitrates.
Frost or hail damage can greatly reduce the leaf area of
plant. This limits the ability of the plant to convert nitrate to protein,
so the plant will accumulate nitrate. As temperatures cool down to 50
degrees and below, the conversion of nitrate to protein is reduced thus
increases nitrate accumulation. Younger plants usually contain higher
nitrate levels, but dry conditions and high soil levels of nitrate can lead to
potential problems in mature plants. Plant leaves and grain do not contain
appreciable levels of nitrate. The highest concentration of nitrate is in
the lower stalk.
Unlike prussic acid, nitrates do not dissipate when forages
are put up for hay. Harvesting at a more mature stage can reduce the
concentration of nitrates, and ensiling forages may reduce nitrate
concentrations by 40 to 60% during the fermentation process.
Plateau has received a section 18 label for North Dakota from August 1, 2001 to December 31, 2001. Plateau has shown very good control of leafy spurge with fall applications. The following bullet points are supplied by BASF.
For best control of leafy spurge, apply prior to leafy spurge losing its milky sap flow due to a killing frost. To check to see if the milky sap flow has been affected by a frost, break the main stem of the leafy spurge. If milky sap flows from the break, Plateau can still be applied. You will receive excellent control up to and even after several frosts as long as there are leaves present when making your application.
The Plateau Section 18 label suggests a use rate of 8-12 oz/acre. There are several factors that should guide your decision on rate selection. There has been excellent long-term sustainable control of leafy spurge a 8 oz/acre in Western North Dakota. In other areas, a minimum of 10 oz/acre is recommended for any stand of leafy spurge older than 3 years or has greater than 30% canopy coverage. For stands that have 80% or higher canopy coverage and/or older than 5 years in age apply Plateau at 12 oz/acre.
Most grass species show excellent tolerance to Plateau however, there are a few grass species that are not tolerant to Plateau. You can expect significant injury to occur on applications over Timothy, Mountain and Meadow Brome and Orchardgrass. Smooth Brome Grass could be delayed in green up. Other established grasses such as the Bluestems, Wheatgrasses, Kentucky Bluegrass, Blue Grama, Sideoats Grama, and Rye grasses are tolerant. Most forbes and legumes are also tolerant (this includes Alfalfa and range species such as Lupine and Sage).
All applications require the addition of 1 quart methylated seed oil (MSO).
There is significant antagonism between Plateau herbicide and growth regulator herbicides such as Tordon and 2,4-D.
Antagonism may be seen in areas that have had a Tordon
application in the previous 10 months.
Please Contact Our Office For Additional Information
E-mail: griggs@ndsuext.nodak.edu
Go to the 2001 AgAlert Index Page