Growth & Development

Weather’s Impact on Corn Development

Mother nature sure has not been very cooperative this spring!  My weather station near Centerburg has recorded 8.8 inches of rain for the Month of May and 1.7 in. for June (through 6/25).  The 5 year average for May is 4.85 in. and June 4.46 in.  Looking at the 2 month totals for May and June we have had 10.5 inches.  The 5 year average for both months is 9.3 inches.  While we are only received a little over an inch of rain above normal for these 2 months, I think we would all like to forget the month of May.

The extremely wet conditions in May significantly delayed planting.  This week I have seen corn anywhere from V2 to V8.  The table below shows the approximate growing degree days from planting to the various growth stages.  At one of our plots, from April 21st (planting date) through June 19th we have accumulated approximately 872 GDD’s.  Assuming tasseling will happen around 1420 GDD’s we are about 61% complete.

You can access local weather information  anytime at: https://u.osu.edu/knoxcountyag/knox-county-weather-station-data/

The table below shows the approximate Growing Degree Days (GDD’S) required for a corn plant to progress through the different stages of development.

Table 1. Corn GDD’S by growth stage.

Wheat Management for Spring 2025

Today managing your wheat crop requires knowledge of the different growth stages of the plant.  Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications.  Each week throughout the rest of the growing season I will discuss the various wheat growth stages I am seeing in our wheat fields and management issues at each stage.  This week I will focus on Feekes 9 and 10. Most of our wheat has progressed to the Feekes 9 growth stage,  some fields are or soon will be in Feekes 10 growth stage.

Feekes 9 – Ligule of flag leaf visible.

The flag leaf is completely emerged from the whorl. Flag leaf and the next-to-last leaf (penultimate leaf ) combined account for 70 to 90 percent of the photosynthates used for grain fill and must be protected for the plant to develop to its full potential.

 

Management.

Scout for insects and diseases. Consider a fungicide application to protect the flag leaf if foliar diseases are present on the lower canopy. Nitrogen application can increase grain protein levels.

Feekes 10 – Boot.

The head is inside the leaf sheath giving it a swollen appearance.  The flag leaf sheath and peduncle elongate and the developing head is pushed through the flag leaf sheath.  Temperatures below 28 degrees Fahrenheit may cause damage to the developing head.

 

Management.

Scout for insects, weeds, and diseases. Application of 2,4-D after wheat reaches the boot stage of growth can result in trapped heads, missing florets, or twisted awns.

Wheat Management for Spring 2025

Today managing your wheat crop requires knowledge of the different growth stages of the plant.  Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications.  Each week throughout the rest of the growing season I will discuss the various wheat growth stages I am seeing in our wheat fields and management issues at each stage.  This week I will focus on Feekes 7. Most of our wheat has progressed to the Feekes7 growth stage, some fields are approaching Feekes 8 growth stage and beyond.

Feekes 7 Growth Stage – Second Node Visible.

At the Feekes 7 growth stage, the second node is visible above the soil surface. These nodes are usually seen as clearly swollen areas of a distinctly different (darker) shade of green than the rest of the stem. Wheat will still respond to nitrogen fertilizer applied at Feekes 7 if weather prevented an earlier application; however, mechanical damage may occur from applicator equipment. A video demonstrating for identifying Feekes 7 and 8 growth stages can be found here: https://www.youtube.com/watch?v=bnV57AhUt-Y&list=PLYlh_BdeqniJ8oD8TnyGhQHRd96ptV0Yt&index=2

Management

Plant growth regulators may be applied at this growth stage.  Scout for insects, weeds, and diseases.

Effect of standing water and saturated soils on corn growth

Source: Agronomy eUpdates

 

If corn has been planted, standing water or saturated soil conditions in areas of a field can produce impacts now or later for corn. Periods of early-season water saturation can cause immediate problems for small corn plants and can have season-long implications as well. Hopefully, the affected areas are small and confined to spots that are low-lying or poorly drained. While heavy rains and respective standing water have been limited to areas of northwest, northeast, and southeast Kansas, the coverage is expected to increase into mid-May. Precipitation is forecasted across most of the state with an emphasis on western Kansas, where upwards of 2-3 inches is possible. In addition to this above-normal moisture, temperatures will be cooler than normal with extensive periods of clouds. Thus, the extent of inundated corn may potentially increase as a result.

Factors affecting flood damage to corn include

  • corn growth stage,
  • the duration and frequency of saturated or standing water, and
  • air and soil temperature while water is standing.

Saturated soil after corn emergence

After corn emerges, saturated soils inhibit root growth, leaf area expansion, and photosynthesis because of the lack of oxygen and cooler soil temperatures. Yellow leaves indicate a slowing of photosynthesis and plant growth. Leaves and sheaths may turn purple from the accumulation of sugars if photosynthesis continues but growth is slowed. Corn plants can recover with minimal impact on yield if the plants stay alive and conditions return to normal fairly quickly.

Although root growth can compensate to some extent later in the season, a saturated profile early in the season can confine the root system to the top several inches of soil, setting up problems later in the season if the root system remains shallow. Corn plants in this situation tend to be prone to late-season root rot if wetness continues throughout the summer, and stalk rots if the plants undergo mid- to late-season drought stress. Plants with shallow root systems also become more susceptible to standability problems during periods of high winds.

Tolerance of young corn plants to full submersion

Young corn plants can tolerate only a few days of full submersion. In some cases, symptoms and stand problems seen late in the season may trace back to flooding when the plants were young. Before V6, when the growing point is at or below the soil surface, corn can survive only 2-4 days of flooding. The chances of plant survival increase dramatically if the growing point was not completely submerged or if it was submerged for less than 48 hours. After 48 hours of soil saturation, soil oxygen is depleted, and critical plant functions (photosynthesis, water uptake, and nutrient uptake) are impaired.

Thus, young corn plants are more susceptible than corn beyond the V6 stage, when the plants are taller and the growing point is above the surface. Research has demonstrated yield reductions from early-season flooding ranging from 5% to 32%, depending on soil nitrogen status and duration of flooding.

Complicating factors

Temperatures can influence the extent of damage from flooding or saturated soils. Cool, cloudy weather limits damage from flooding because growth is slowed and because cool water contains more oxygen than warm water. Warm temperatures can increase the chances of long-term damage.

Silt deposition in the whorls of vegetative corn plants can inhibit the recovery of flooded corn plants. Enough soil can be deposited in the whorl that the emergence of later leaves is inhibited. A heavy layer of silt on leaf surfaces can potentially inhibit photosynthesis or damage the waxy surface layer of the leaf (cuticle), making the leaves subject to drying out. New leaves should not be affected if they can emerge normally. Ironically, what is often best for the silt-covered plants is to receive a small shower to help wash off the leaves.

In some instances, the soil in the whorl may contain certain soft-rotting bacteria. These bacteria can cause the top of the plant to rot. The whorl can easily be pulled out of a plant infected with these soft-rotting bacteria. In addition, a rather putrid odor will be present. These plants will not recover.

Disease considerations

Flooding can increase the incidence of moisture-loving diseases like crazy top downy mildew. Saturation for 24 to 48 hours allows the crazy top fungus spores found in the soil to germinate and infect flooded plants. The fungus grows systemically in the plant, often not causing visual symptoms for some time. Symptom expression depends on the timing of infection and the amount of fungal growth in the plant. Symptoms include excessive tillering, rolling and twisting of upper leaves, and proliferation of the tassel. Eventually, both the tassel and ear can resemble a disorganized mass of small leaves, hence the name “crazy top.”

Other concerns: Denitrification, cold weather crown stress, green snap, and root lodging

Saturated soils can also cause loss of N fertilizer by either denitrification (loss of N to the atmosphere, mainly as nitrous oxide gas) or leaching (movement of N beyond the rooting zone). For any of these losses to occur, N should be present in the mobile nitrate (NO3–) form. Depending on the fertilizer application time and source, most of the N may still be in the stable ammonium (NH4+) form. However, the conversion to nitrate happens quickly as soil temperature continues to increase. Under wet spring planting conditions, corn may respond to in-season N applications if a large portion of early-applied N is lost to these processes. If corn remains N deficient later in the season, expect considerably higher levels of stalk rot.

Another condition associated with extended periods of cool, wet soils is commonly referred to as cold weather crown stress. Internal stalk cells in the crown nodes can become “leaky” when cell membranes become chilled and oxygen is limited because of the saturated soils. Hybrids with “southern” genetics are more susceptible to this problem than are northern types. Plants may recover from this damage, but they will be much more susceptible to stalk rot later in the season if hot, dry temperatures occur, since water and nutrients cannot be efficiently moved through the damaged crown.

Sidewall compaction from planting into wet soils

Source: Agronomy eUpdates

Figure 1. Sidewall and seed zone compaction in heavy clay soil.

Conducting field work — including planting, tillage, or traffic in general — after wet weather can cause soil compaction, particularly sidewall compaction in the seed furrow. The worst cases of sidewall compaction are seen after a field has been planted when the soil was too wet, followed by a period of dry weather. If the soil stays moist, the roots can usually grow through the walls of the seed furrow. However, if the soil gets dry, the roots can have a harder time growing through that seed furrow wall, and instead grow along the furrow, resulting in what is referred to as sidewall compaction.

With corn, the plants might look fine for a while, but the symptoms of this problem will probably show up after the plants reach several inches tall. Symptoms can mimic drought stress, nutrient deficiency, or both.

Since there are not any good ways to fix sidewall compaction once it exists, the best practice would be to avoid creating the problem in the first place. This means waiting until soils are dry enough to plant. The way to test for this is to dig down to the desired planting depth and make a ball with the soil. Next, see if the ball will crumble or crack apart, or if it deforms like molding putty. If it crumbles, it is ready to plant. If it deforms, it would be best to wait before resuming field operations. Even waiting as little as half a day could make a big difference.

Other considerations

  • Planting too shallow: Planting shallow in wet soil may lead to wheel compaction below the seedling depth. This results in limited downward root growth and seeds growing horizontally.
  • Too much down pressure: If you must work in wet soil, then the down pressure of the row unit and press wheels needs to be reduced to limit compaction around the seed.
  • Soil structure: Tilled soils often lack proper soil structure, causing the standard closing wheel to pinch the sidewalls over the seed from additional pressure. This is frequently a concern in heavier-textured soils, i.e., higher clay content.

Wheat Management for Spring 2025

Today managing your wheat crop requires knowledge of the different growth stages of the plant.  Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications.  Each week throughout the rest of the growing season I will discuss the various wheat growth stages I am seeing in our wheat fields and management issues at each stage.  This week I will focus on Feekes 6.  Most of our wheat has progressed to the Feekes 6 growth stage, some fields are approaching Feekes 7 growth stage.

Feekes 6 – First Node Visible. 

Prior to Feekes 6.0, the nodes are all formed but sandwiched together so that they are not readily distinguishable. At 6.0, the first node is swollen and appears above the soil surface. This stage is commonly referred to as “jointing.” Above this node is the head or spike, which is being pushed upwards eventually from the boot. The spike at this stage is fully differentiated, containing future spikelets and florets.

Split wheat stem showing developing spike.

You can remove and carefully examine plants for the first node. It can usually be seen and felt by removing the lower leaves and leaf sheaths from large wheat tillers.  A sharp knife or razor blade is useful to split stems to determine the location of the developing head. The stem is hollow in most wheat varieties behind this node.

 

 

Management.

By Feekes 6.0, essentially all weed-control applications have been made. Do not apply phenoxy herbicides such as 2,4-D, Banvel or MCPA after Feekes 6.0, as these materials can be translocated into the developing head, causing sterility or distortion. Sufonyl-urea herbicides are safe at this growth stage, but for practical reasons, weed control should have been completed by now. Small grains can still show good response to N topdressing at this time.

Corn Growing Degree Days

Mother Nature is finally cooperating, and planting is off to a great start.  A common question is, “After planting how long before I can see corn?”  Once corn is in the ground, you can expect to see emergence around 100 growing degree days after planting. The Table below lists the approximate growing degree days for various corn growth stages.

New this year!  I will have a weather station set up by some of our research plots near Centerburg.  Click here to access our local weather data. This weather data should be able provide information to assist with many of your daily activities such as: spraying records, crop growth & development, insect scouting, anticipated disease pressure, and many more.

Wheat Management for Spring 2025

Today managing your wheat crop requires knowledge of the different growth stages of the plant.  Growth stage identification is critical for scouting and proper timing of fertilizer and pesticide applications.  Each week throughout the rest of the growing season I will discuss the various wheat growth stages I am seeing in our wheat fields and management issues at each stage.  This week I will focus on Feekes 5.  Most of our wheat has progressed to the Feekes 5 growth stage, some fields are in Feekes 6 growth stage.

Feekes 5 – Leaf sheaths strongly erect. 

 

The beginning of the stem elongation phase.  The pseudo-stem is strongly erect and leaf sheaths are elongated. The developing head reaches the terminal spikelet stage and is pushed up into the pseudo-stem.

Terminal spikelet occurs at Feekes 5. This stage marks the completion of the spikelet initiation phase. At this stage, the number of spikelets per head has been determined.   Stress during this stage can reduce total number of kernels per head.

The first hollow stem stage occurs when there is approximately 0.6 inch of hollow stem below the developing head.  Crop water use is about 0.1 inch per day.

Management.

This is an ideal stage for spring topdress nitrogen application. Weed control efforts should be made prior to or during Feekes 5.0 with 2,4-D and other labeled herbicides. This is also a good stage to begin scouting for foliar diseases.  Tillers developing after this time are not expected to contribute to yield.

Harvest Delays – Light vs. Temperature

There has been a lot of discussion about the crop yields from 2023 in Ohio, from early reports of crop stress in May and June to greater than anticipated yield values for many producers this fall. Yield reports of >110 bu/ac wheat harvested in July were reported in parts of Ohio, and better than anticipated yields in some corn and soybean fields. Harvest progress of corn has been delayed from normal for many farmers.

Many questions have been raised on the role that haze from Canadian wildfires may have played on seasonal crop growth this year. Ohio experienced three major episodes of wildfire impacts on June 6-7, June 27-29, and July 16-17, with several more days throughout the two-month period of less intense smoke-filled skies. However, looking at 2023 compared to historical trends overall radiation availability was similar to the 10-year historical average for the three CFAES research stations of Northwest, Wooster, and Western (Figure 1). Light availability was higher than normal in May through mid-June, in part due to many clear days and below average rainfall. Light availability approached normal levels throughout June and July in part due to a slight reduction during the short period of haze, but recovered to mimic the 10-year patterns observed in recent past.

Despite the short haze periods, the photons available per heat unit accumulated (PTQ or photothermal quotient) were at or above the 10-year average (0-38% greater) aside from July at Western research station (6% lower) and September at Northwest (2% below normal). Generally, greater PTQ values suggest that more photosynthesis can occur in the same thermal period and could lead to greater yields.

Figure 1. Daily light integral (left) and accumulated growing degree days, base 50°F (right), and the 10-year averages for three Ohio locations of Northwest Agricultural Research Station in Custar (upper row), Western Agricultural Research Station in South Charleston (middle row), and the Ohio Agricultural Research and Development Center in Wooster (bottom row) in 2023.

Contrastingly, accumulated Growing Degree Days (GDDs) were below the 10-year average for every location this year (Figure 2). The same pattern that brought the frequent spells of wildfire smoke, northerly wind flow out of Canada, kept temperatures below average for the summer (Figure 2 – left). It is possible the cooler temperatures helped crop’s periods of water deficit better this year than in years past, but also can have contributed to the slow drydown experienced by many farmers this year.

Interesting to note, several folks have commented that this summer reminded them of the summer of 1992. Looking at that year’s temperature difference compared to average (Figure 2 – right), temperatures were cooler in 1992 than this past summer. Mt. Pinatubo erupted in June 1991 and is often pointed to as a main reason for cooler global temperatures in the year that followed. Volcanic emissions circled around the globe high in the atmosphere throughout the tropical and sub-tropical regions, reflecting and absorbing solar radiation and cooling the Northern Hemisphere surface temperatures by about 0.9-1°F.

Overall, the cooler temperatures and slower accumulation of GDDs can be the largest contributor to delayed corn harvest this year. Cooler overall conditions could have led to slightly higher than normal PTQ values for the season, which also may help explain the higher than anticipated yields in the wheat crop this summer.