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AgAlerts 2002 From Griggs County
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Issue # 5, May 23, 2002
White Soils Abundant in Griggs County Dates for Tractor Safety Schools
Soybean Iron Chlorosis Minimum Stands For Crops (NDSU Crop & Pest Report)
As the frost has gone out, we have seen large areas in fields turn white with
salt accumulations. This is due to the high water tables we have been
experiencing since 1993. These areas of high salt accumulations will have
an effect on seed germination and seedling growth. For a better
understanding how salts accumulate link to Extension publication "Managing
Saline Soils in North Dakota" (SF1087). For information on crop
tolerances and yield reductions link to NDSU ProCrop.
The first step in managing these areas is to get something growing to try and
lower the water table. Deep rooted barrier crops such as alfalfa planted
between the water source and discharge area, have helped reduce the size and
salt levels. These areas have taken several years to get to this
point and there are no overnight solutions. Management strategies will
have to be developed to get this problem reduced in following years.
With the abundance of saline areas this year
along with cool weather conditions could lead to iron chlorosis problems in
soybeans. There are several varieties on the market now with good iron
chlorosis tolerance. But if were not the variety of choice, be aware of
possible problems.
Chlorosis associated with iron deficiency does not appear
until the first trifoliate leaves appear in the plant. There are several factors
which contribute to this problem. The first important and undisputed factor is
the presence of free carbonates, particularly bicarbonate which is a product of
the combination of water and carbonate minerals in the soil. Bicarbonate
solubility is low, and contrary to logic increases in concentration as the soil
becomes wet. So in dry years and dry periods, chlorosis can be relatively minor,
because bicarbonate levels interfering with plant uptake of iron are low. As the
soil becomes more moist, bicarbonate concentrations increase and the plants
become less able to take up iron.
The phenomena of wheel tracks being yellow or green compared
to the rest of the field is probably the result of soil wetness under the
tracks. In dry conditions, the soil tends to be more moist under tracks because
of capillary pull of water into the track similar to the press wheels of a
planter pulling moisture into the seed zone. More moisture, more bicarbonate,
more chlorosis. In wet years, wheel tracks and compacted areas tend to dry
first, thence less moisture, less bicarbonate, green tracks. The following
factors are stress factors that make the plants less able to take up iron in
adverse circumstances; cool weather and soluble salts. Cool weather slows down
plant systems, including iron uptake and plants tend to increase in chlorosis
during cool periods when soils are moist and carbonates are present. Soluble
salts have also been shown to be a major factor in contributing to the presence
of chlorosis with supposedly iron chlorosis tolerant varieties. Often, carbonate
levels and soil moisture are similar, but the presence or absence of salts has
been the difference between whether chlorosis appears or not.
The open, warm winter followed by the months
of April and May where there were a high number of temperature fluctuations,
might have caused some alfalfa stands to be injured. Duane Meyer, NDSU
plant science professor, has had several reports of winter kill in eastern North
Dakota. The couple of fields I was in showed some injury. The injury
was in the form of killed crowns and also young growth with frost damage.
The question arises "at what level of stand reduction do I tear up the
alfalfa"? According to Duane Meyer, fields where there are between 40
and 50 healthy stems per square foot, producers can expect production. In
fields with less than 20 stems per square foot, especially if this density
pattern is widespread across the entire field, producers should rotate the old
alfalfa ground to a cereal crop that can utilize the nitrogen produced by the
alfalfa.
To check whether an alfalfa plant is still healthy, dig up a
few plants and healthy roots should be firm and white. A tap root with a
black streak running down its center indicates a plant infected by Fusarium root
rot, a condition generally unrelated to winter injury or winter kill.
Fusarium root rot is prevalent in alfalfa fields throughout North Dakota, and
plants infected with the disease are still capable of growing adequately, but
vigor has been compromised. A tap root that is yellowish in color with a
soft, cork-like texture is dead, the result of winter kill.
Planting a new alfalfa crop into the old alfalfa ground is
risky. Alfalfa contains an autotoxic compound that can stunt or kill
alfalfa seedlings. Use new ground and go for seeding-year forage.
New-crop alfalfa will produce a harvestable stand in about 70 days.
Picture of a healthy plant, winter injury and frost injury.
Colorado spruce trees are being attacked by Rhizosphaera kahlkoffii and Cytospora canker. The wet conditions along with high humidity over the last few years has been an ideal environment for the development and spread of these diseases. The above links will provide more information concerning the specific disease. The following pictures are of Cytospora canker at the Cooperstown Country Club. If the disease progresses to this point, the trees should be removed due to their looks and they are a source of infection to other trees.
(click to enlarge)
This disease appears as rings of dark green grass surrounding areas of dead or light-colored grass. The rings are produced by any one of over 50 different kinds of fungus. The dying grass inside a ring is caused by lack of water penetration. Conditions that favor fairy rings are soils that contain undecomposed, woody organic matter, such as dead tree roots or old construction materials. To control fair rings is difficult. Applying adequate fertilizer will try to hide the problem. Aerate rings and use a wetting agent to improve water penetration. In extreme cases, you can dig up the entire area of the ring and find the undecomposed organic matter and replant. The following link will provide more information on Fairy Rings.
Pictures of fairy rings in the Griggs County Courthouse lawn problem from
trees that were removed.
Please Contact Our Office For Additional Information
E-mail: griggs@ndsuext.nodak.edu
Go to the 2002 AgAlert Index Page