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Nitrogen Deficiency in Soybeans

Credit: Michigan State University

Even as nitrogen-fixing plants, nitrogen deficiency in soybeans can be problematic for farmers. Soybeans can fix up to 50% of their own nitrogen while the other 50% is sourced from soil. Root development and soil health are key drivers of nitrogen deficiency.

A primary cause of nitrogen deficiency is poor inoculation. Rhizobia – the nitrogen-fixing bacterium responsible for prompting nodulation – cannot survive well in coarse, sandy or saturated soils. Cold and wet soils can also suppress rhizobia activity and reduce nodulation.

Soils with low pH can prevent root nodulation and reduce nitrogen absorption Flooding or highly saturated soils can also prevent nitrogen uptake, even if nodulation occurred successfully.

Scouting for Nitrogen Deficiency

Nitrogen is a mobile nutrient, moving throughout the entire plant. It moves to the newest leaves first, leaving the oldest leaves more susceptible to deficiency. In nitrogen-deficient soybeans, the lowest leaves will appear a pale shade of green or show signs of yellowing. Some leaves will also have dark green veins.

Be sure to check nitrogen levels in the soil before R1. As nodules can appear as soon as V1. Check the health of nodules by squeezing them open. If A pink color on the inside indicates that nodules are active and healthy.

Treatment and Implications

A single bushel of soybeans uses 4.2 pounds of nitrogen. Purdue University observed a 38% decrease in yield from nitrogen deficiency – a decline from 65 bu/acre to 40 bu/acre. Rhizobia population can carry over from season to season and continue to support soybean growth. We advise applying inoculant in fields where soybeans have not recently grown. The inoculant can help to stimulate rhizobia activity and promote nodulation.

It is advised to apply 20 to 40 pounds of nitrogen per acre during the R3 growth stage. However, applying nitrogen at planting – especially too much nitrogen – does not increase yield and can actually reduce nodulation. It’s important to determine the best nitrogen application and treatment plan to fit your unique needs. Contact your Data Forard™ Advisor or Latham Representative to discuss your options.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Crop, Season, Soybeans, Spring
Latham Hi‑Tech Seeds

Iron Deficiency Chlorosis in Soybeans

Iron deficiency chlorosis (IDC) is a disorder that appears in soybeans during the early stages of the growing season. IDC can reduce yield and lead to stunting if it goes unaddressed year to year. Every year, farmers lose over $100 million to IDC and yield loss estimates range from 20-30% in severe cases.

Credit: Soybean Research Information Network

What to Look For

Iron is an essential nutrient that supports key plant functions including nodulation, energy transfer and plant metabolism. Iron deficiency can reduce the absorption of other essential nutrients including nitrogen. Deficiency in iron prevents chlorophyll from forming which leads to the yellowing of leaves.

In soybeans with IDC, the youngest leaves will begin to turn yellow or white while the veins remain green. Unlike mobile nutrients such as nitrogen or potassium, iron is immobile within the plant. As a result, yellowing and signs of IDC will only be seen on newer growth. Beyond yellowing, severe cases of IDC can cause leaves to turn brown.

Causes and Implications

Upon testing, soils may have abundant levels of iron, but must be in a usable form. Wet soils, salty soils and soils with high pH (greater than 7.5) will cause IDC to occur as these factors prevent iron absorption. Calcareous or chalky soils are also favorable conditions for IDC.

IDC occurs most often in shallow areas that are wet where salts and carbonates have built-up overtime. Under these conditions, calcium particles bind to the soil, making the iron inaccessible to soybeans. Calcium carbonate neutralize acid in roots that is needed to make usable iron. For this reason, soils containing limestone with carbonate levels higher than 5% can make iron insoluble.

High nitrates can worsen IDC since absorbing nitrogen decreases the amount of usable iron. Fields with over 100 pounds of nitrogen per acre can be problematic for soybeans and lead to IDC.

Treatment

IDC cannot be managed in-season. We recommend selected a portfolio of defensive varieties to fight this in your fields. Check our line of Ironclad™ soybeans. Our Ironclad brand has been designed to fight this disorder.

Reducing stress levels for soybeans is critical for preventing IDC or worsening its impacts. Other factors including compaction, over-tillage and herbicide injuries can make soybeans more susceptible to chlorosis or lower their chances of overcoming the deficiency.

Soybean varieties that are resilient to IDC should be planted, especially if a field has produced soybeans with chlorosis in the past. In addition to selecting the right varieties, planting iron-coated seeds can be a way to combat the onset of IDC. In-furrow application of iron chelate fertilizer can also address IDC.

Rotational planting or companion cropping with oats are also solutions for preventing IDC. Intercropping soybeans with oats and wheat can reduce levels of soil nitrates that would otherwise lead to chlorosis. Contact your local Latham Representative to determine a treatment plan that meets your specific needs.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Crop, Season, Soybeans, Spring
Latham Hi‑Tech Seeds

Armyworms and Cutworms in Soybeans

Armyworms and cutworms are known to reduce soybean stand and yield by feeding and cutting. Armyworms damage leaf tissue while cutworms clip young plants just above the soil. These worms are differentiated by their appearance.

Black Cutworm (Credit: Iowa State University)

Cutworm

Soybean cutworm species include dingy cutworm, variegated cutworm and black cutworm. Cutworms begin feeding on winter weeds before moving to soybean plants. Cutworms will burrow in the soil surrounding injured plants. Smaller larvae will feed on leaves and larger larvae will cut the plants.

Scouting and Treatment

Dingy Cutworm (Credit: Purdue University)

Begin scouting for cutworms at emergence. The most common signs of cutworm infestation are cut plants, discoloration or wilting leaves. Reduced tillage, no-till and corn on corn rotations can make cutworm infestation more likely. Legume cover crops can also attract cutworms. This protective vegetation should be removed from the soil at least two weeks before planting.

Mature soybeans are the most resilient to yield loss from cutworms. As advised by researchers from Iowa State University, insecticide treatment should also be applied if more than 20% of feeding damage is observed and larvae are smaller than ¾ inch in length.

Yellowstriped Armyworm (Oklahoma State)

Fall Armyworm (University of Tennessee)

Armyworm

The yellow-striped armyworm and fall armyworm are two popular armyworm species. Armyworms grow to be two inches long and feed on both soybean leaves and pods.

Scouting and Treatment

Typically, only one generation of armyworms can be produced in the Midwest due to their inability to overwinter in the cold. Armyworms like to seek shelter in winter annual weeds and grasses. Poorly drained fields can also be an attractive environment for armyworms to dwell.

Applying insecticide is recommended when armyworms are less than one inch. Once armyworms mature and exceed 1 ¼ inches in size, they will stop feeding so it is unnecessary to apply insecticide. Contact your local Latham Representative to assess the best options for treating armyworm and cutworm infestation in your soybeans.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Crop, Insects, Season, Soybeans, Spring
Latham Hi‑Tech Seeds

Fall Frost Damage in Corn and Soybeans

Frost damage occurs in corn and soybeans when plants are exposed to freezing or below-freezing temperatures. Damage can occur to the plants above and below the soil when temperatures range from 28 to 32°F and colder. Corn and soybean plants exposed to air temperatures below 28°F are often lethal and prevent plants from undergoing full recovery from injuries. The key in assessing frost damage is waiting five days to allow for any potential growth recovery or rehabilitation to occur.

Credit: Michigan State University

Fall Frost in Soybeans

Once soybeans begin maturity and already have developed pods, they are most often immune from frost injury. Soybeans placed in narrow rows can have more protection from freezing air temperatures in being covered by leaf canopies. Pods growing on the lower portion of the plant are less vulnerable to frost damage than those on the top part of the canopy. Injured soybeans exhibit elongated pods that shrink to smaller than normal sizes upon drying. Most yield loss occurs during the full seed maturity stage.

Soybeans damaged by frost should be dried at a temperature no higher than 130°F and may have lower oil content. Both frost damaged corn and soybeans may also have delayed dry down.

Credit: University of Minnesota

Fall Frost in Corn

Frost-damaged corn can exhibit softened kernels prone to breakage and should be dried at temperatures below 160°F and be stored at a moisture level no higher than 14%. The storage life for frost-damaged corn will be cut in half and damaged corn should be handled separately from uninjured corn.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Corn, Crop, Fall, Frost, Season, Soybeans, Weather
Latham Hi‑Tech Seeds

Imbibitional Chilling

Causes of Imbibitional Chilling

Imbibitional chilling occurs during the process by which crops absorb water prior to germinating, a phase known as imbibition. Under optimal conditions, seeds should be planted when soil temperatures are above 55°F. When seeds are planted in soils below optimal temperature, the uptake of cold water can damage cells and cause seeds to rupture. This can lead seeds to become shriveled and cause seedlings to emerge late, in a corkscrew shape, or not at all.

If an injured seed eventually develops into an emerged seedling, it can become more vulnerable to disease or damage from herbicides. The risk of imbibitional chilling especially increases when soil temperatures fall below 50°F. Imbibitional chilling or cold injury can occur within 24 to 36 hours of planting, making the relationship between planting timing and soil temperature critical.

Preventing Chilling Injury

As the injury to seedlings occurs after planting, there is little preventive action that can be taken aside from planting when soil temperature is optimal. In the best case, if enough time is afforded between planting and the drop in soil temperature, a seed is less likely to undergo chilling if it is able to absorb warm water. There are ways to determine if imbibitional chilling has occurred after planting. When scouting, look for signs of inconsistent emergence. If a plant looks to be missing, dig into the soil around the area to see if a seedling can be found. If it has a corkscrew shape, underwent leaf emergence below ground, or is missing parts, these are also signs of imbibitional chilling. Delayed emergence of a seed can be the result of reduced seed vigor that can result from imbibitional chilling.

Soil temperatures should be monitored and averaged for the week preceding the projected planting date. To determine the soil temperature on the chosen planting day, take the temperature of the soil just after sunrise – the coldest part of the subsequent 24-hour period. Soil temperature changes more slowly than air temperature, but air temperature can still be a strong indicator for what to expect with soil temperature. If it is projected that soil temperature will remain above 50°F for 24 to 48 hours after planting, imbibitional chilling can be avoided.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Corn, Crop, Emergence, Soybeans, Spring
Latham Hi‑Tech Seeds

Protect Soybeans from Cold Temperatures
Many of our minds are already on the upcoming planting season. This week someone posed the following question, “How hard of a frost can soybeans withstand?”

It’s a great question, so I wanted to address the topic of early planting a bit, well, “earlier” than usual!

The first thing to keep in mind is that cold temperatures at or before planting can negatively affect the growing point of the plant. For corn, that growing point stays under the soil surface until the V5-V6 stage, helping protect the plant to a certain degree from colder weather spells for several weeks. For soybeans, however, the growing point comes out of the ground at emergence. Therefore, a soybean seedling is immediately vulnerable to cold weather.

Using a fungicide seed treatment will help protect young soybeans from seedling diseases at this early stage, but they are not designed to protect against cold temperatures. Soybeans typically require over 100 growing degree units (GDU’s) to accumulate before emergence, which is similar to corn that requires about 125 GDU’s. Abiding by the minimum soil temperature of 50 degrees Fahrenheit will keep you away from poor emergence and the seedling disease risk associated with soil temps below 50 degrees. That’s why I suggest watching the weather forecasts before you plant soybean seed, and do your best to ensure hard frosts (which take place at 28 degrees Fahrenheit) are no longer possible.

Remember, when soybeans emerge, they have a growing point at the base of each cotyledon and at the main shoot. The main shoot is the small leaves in-between the cotyledons. If you notice brown on the stem below the cotyledons, the plant will not recover. Early planting is proven to provide higher yields, but it is is fine balance between the two, so watch weather forecasts and soil temperatures so you can find the balance on your own farm.

Additional tips to keep in mind before planting:
1. Grab a clump of soil and watch how easily it crumbles. If it stays in a ball, conditions are NOT right for planting. If it crumbles easily, the soil is fit for planting.
2. Make sure your planting date is covered in your farm insurance policy – this includes your “do not plant before” dates. If you plant outside those dates, your insurance could be jeopardized.
Phil Long

April 1, 2019

Agronomics, Crop, Emergence, Frost, Season, Soybeans, Tech Tuesday, Weather, Winter
Latham Hi‑Tech Seeds

Spring Frost Damage in Corn and Soybeans

Frost damage occurs in corn and soybeans when plants are exposed to freezing or below-freezing temperatures. Damage can occur to the plants above and below the soil when temperatures range from 28 to 32°F and colder. Corn and soybean plants exposed to air temperatures below 28°F are often lethal and prevent plants from undergoing full recovery from injuries. The key in assessing frost damage is waiting five days to allow for any potential growth recovery or rehabilitation to occur.

Spring Frost in Soybeans

If frost damage occurs below the soybeans’ cotyledons – the first leaves that emerge above ground – the plant will mostly likely fail to recover. Wilted and dried leaves will often remain on the plant after a frost event. In recovering soybeans, new leaves will emerge at the site of cotyledons – the first pair of embryonic leaves that appear above ground. If auxiliary buds growing at the juncture of the plant’s stem and cotyledons are not frozen, the plant is on track for recovery.

Spring Frost in Corn

Since corn plants are protected by soil for a longer period of time relative to soybeans, they are less susceptible to lethal frost injury. However, temperatures below 28°F can cause damage below the soil and compromise growth, leading to poor stands. Once the growing point is above ground, corn plants exposed to 32°F for a few hours and 28°F for a few minutes can be lethal. After an initial frost, continued cool temperatures can decrease yield due to the onset of stalk rot diseases.

If frost occurs before V6, yield loss is minimal. In recovering corn plants, you should see new leaf growth emerging from whorls. Yellow-colored tissue that exists above the growing point is a sign of regeneration.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Corn, Crop, Frost, Soybeans, Weather
Latham Hi‑Tech Seeds

Flooding and Saturated Soils

iStock Photo

For corn and soybean plants before and after emergence, flooding and saturated soils can jeopardize yield. Germinating seeds require oxygen to survive. After the first 48 hours following a heavy rain or flooding event, oxygen levels in the soil will become entirely depleted and prevent seeds from germinating and continuing to grow.

Yield loss for corn and soybeans depends on the duration of the flooding event and at what growth stage it occurs. The longer a plant is submerged or growing in saturated soil, the less likely it is to survive. Generally, smaller seedlings with lower stamina are less likely to survive following a heavy rainfall event compared to larger seedlings.

Warmer temperatures are associated with higher growth rates, and as a result, a higher amount of oxygen is used. When temperatures exceed the mid-70° range, survival may not exceed 24 hours following the heavy rainfall event.

Effects on Corn Plants

Before V6, the growing point is below ground and damage from flooding is more likely to impact yield or kill the plant.  After V6, corn plants fair better in saturated conditions if some of the plant is out of the water. However, the higher temperatures can speed up respiration and oxygen requirements, leading to more plant damage compared to cooler temperatures during a flood event.

Nitrogen loss is another way flooding impacts corn yields. Corn consumes two-thirds of its nitrogen by the start of the reproductive stage and relies on a functional root system. If a flooding event compromises plant roots, yield can be reduced significantly. Research from Iowa State University found that a 30-inch corn plant that had been flooded for 48 hours with minimal nitrogen uptake experienced a 20% reduction in yield. Flooding can also promote seed decay, crazy top that exhibits proliferated tassels, stunted ears or completely barren plants

Impacts on Soybeans

For soybean plants at stages V2 or V3, survival is possible. However, nitrogen fixation can be restricted and reduced yield is still likely. For soybeans submerged for less than 48 hours, yield loss is rarely observed.

Once the first bloom appears at stage R1 the number of pods per node will be greatly decreased if sitting in saturated conditions. Wilting, stunting and yellow-leaves will be expressed in damaged or dying soybean plants. Further, research has found that greater yield reduction has been observed in soybean plants grown in heavy clay soils as opposed to silt loam soils.

Assessing Outcomes

Flooding and prolonged saturated soils pose the greatest threat to young plants that have yet to emerge above ground. As water recedes, any remaining residual mud on corn and soybean plants can reduce photosynthesis. For plants that survive a flooding event, they will be more vulnerable to diseases and stresses over the course of the growing season.

The survival outlook for saturated seeds and germinating plants will not exceed four days. Plants that survive after water levels recede will continue to grow within three to five days.

Latham Seeds Agronomy Team

April 1, 2019

Agronomics, Corn, Crop, Flooding, Soil, Soybeans, Weather
Latham Hi‑Tech Seeds

New Technology Update with John Latham

Join us with John Latham this morning as we talk about NEW Latham Seeds soybean technology available for the 2019 growing season!!

https://www.facebook.com/LathamSeeds/videos/293804974620148?sfns=mo

Laura Cunningham

February 28, 2019

#AskTheAgronomist, Crop, Herbicide Technology, Industry News, Seed Technology, Soybeans
Latham Hi‑Tech Seeds

#AskTheAgronomist: The Love List

On this Valentine’s Day, we are reviewing 7 things we LOVE about the Latham product lineup!

https://www.facebook.com/LathamSeeds/videos/924337164624015?sfns=mo

Laura Cunningham

February 14, 2019

#AskTheAgronomist, Alfalfa, Corn, Corn Silage, Cover Crops, Crop, Soybeans