Growth & Development

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.

Ohio Crop Progress

Source: USDA

Crop maturity accelerated under last week’s warm and dry conditions, according to Ben Torrance, State Statistician, USDA NASS, Ohio Field Office. Topsoil moisture conditions were rated 6 percent very short, 49 percent short, and 45 percent adequate. Statewide, the average temperature for the week ending on September 24 was 63.4 degrees, 2.0 degrees above normal. Weather stations recorded an average of 0.09 inches of precipitation, 0.64 inches below average. There were 6.5 days suitable for fieldwork during the week ending September 24.

Last week’s field activities included hay bailing, manure application, lime spreading, and drainage tile installation. Limited instances of tar spot fungus in corn stands were reported in west-central portions of the State. Seventyseven percent of corn was in or past dent, 40 percent was mature, and 2 percent was harvested. Corn for silage was 59 percent harvested. Fifty-two percent of soybeans were dropping leaves. Corn and soybean condition were 72 and 68 percent good to excellent, respectively. Third cuttings of alfalfa hay and other dry hay were 95 and 80 percent complete, respectively. Fourth cuttings of alfalfa hay were 63 percent complete. Winter wheat was 3 percent planted. Pasture and range condition was rated 56 percent good to excellent, down from the previous week.

Wheat Planting Management Considerations for Fall 2023

This year, wheat yields were extremely high across Ohio. In the Ohio Wheat Performance Test (https://ohiocroptest.cfaes.osu.edu/wheattrials/default.asp?year=2023), grain yield averaged between 86 and 126 bu/acre across five Ohio counties. Cool temperatures and adequate subsoil moisture led to a long grain fill period. The long grain fill period coupled with low disease resulted in high-yielding conditions. Mother nature certainly helped us out in 2023; however, fall wheat management is important to set your crop up for success.

Now that we’ve entered mid-September, wheat planting is just around the corner. Here are our key management strategies for this fall:

  1. Plant within the 10-day period starting after the county fly-safe date. It can be tempting to plant wheat before your county’s Hessian fly-safe date (Figure ; however, the best time to plant wheat is the 10-day period starting the day after the fly-safe date. Planting before the fly-safe date increases the risk of insect and disease problems including Hessian fly and aphids carrying Barley Yellow Dwarf Virus. Our wheat planting date field trials have shown no yield benefit of planting prior to the county fly-safe date.
  2. Select high-yielding varieties with high test weight, good straw strength, and adequate disease resistance. Do not jeopardize your investment by planting anything but the best-yielding varieties that also have resistance to the important diseases in your area. Depending on your area of the state, you may need good resistance to powdery mildew, Stagonospora leaf blotch, and/or leaf rust. Avoid varieties with susceptibility to Fusarium head scab. Plant seed that has been properly cleaned to remove shriveled kernels and treated with a fungicide seed treatment to control seed-borne diseases.
  3. Optimum seeding rates are between 1.2 and 1.6 million seeds/acre. For drills with 7.5-inch row spacing, this is about 18 to 24 seeds per foot of row. When wheat is planted on time, the actual seeding rate has little effect on yield, but high seeding rates (above 30 seeds per foot of row) increase lodging and risk of severe powdery mildew development next spring.
  4. Planting depth is critical for tiller development and winter survival. Plant seed 1.5 inches deep and make sure planting depth is uniform across the field. No-till wheat seeded into soybean stubble is ideal, but make sure the soybean residue is uniformly spread over the surface of the ground. Shallow planting is the main cause of low tiller numbers and poor winter survival due to heaving and freezing injuries. Remember, you cannot compensate for a poor planting job by planting more seeds; it just costs more money.
  5. Follow the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa (https://agcrops.osu.edu/FertilityResources/tri-state_info).
  6. Apply 20 to 30 lb of actual nitrogen per acre at planting to promote fall tiller development. A soil test should be completed to determine phosphorus and potassium needs. Wheat requires more phosphorus than corn or soybean, and soil test levels should be maintained between 30-50 ppm (Mehlich-3 P) for optimum production (Table 1). Do not add phosphorus if soil test levels exceed 50 ppm.

Table 1. Wheat phosphorus recommendations from the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa.

Table 1. Wheat phosphorus recommendations from the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa.

Soil potassium should be maintained at levels of 100-130 and 120-170 ppm (Mehlich-3 K) on sandy soils (CEC < 5 meq/100 g) and loam/clay soils (CEC > 6 meq/100 g), respectively. If potassium levels are low, apply K2O fertilizer at planting, depending on soil CEC and yield potential (Table 2).

Table 2. Wheat potassium recommendations from the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa.

Table 2. Wheat potassium recommendations from the Tri-State Fertilizer Recommendations for Corn, Soybeans, Wheat, and Alfalfa.

Soil pH should be between 6.3 and 7.0. In Ohio, limed soils usually have adequate calcium and magnesium.

Ohio Crop Progress

Source: USDA
Moderate temperatures and mostly clear skies throughout Ohio provided farmers with favorable conditions to conduct pre-harvest activities, according to Ben Torrance, State Statistician, USDA NASS, Ohio Field Office. Continued lack of significant precipitation resulted in an increase in abnormally dry soil moisture levels. Topsoil moisture conditions were rated 6 percent very short, 37 percent short, 56 percent adequate, and 1 percent surplus. Statewide, the average temperature for the week ending on September 17 was 62.3 degrees, 3.1 degrees below normal. Weather stations recorded an average of 0.25 inches of precipitation, 0.59 inches below average. There were 6.1 days suitable for fieldwork during the week ending September 17.
While row crop progress remained behind the five-year average, favorable crop condition ratings exceeded previous year averages. Sixty-seven percent of corn was in or past dent and 22 percent was mature. Corn for silage was 42 percent harvested. Twenty-seven percent of soybeans were dropping leaves. Corn and soybean condition were 76 and 71 percent good to excellent, respectively. Third cuttings of alfalfa hay and other dry hay were 92 and 71 percent complete, respectively. Fourth cuttings of alfalfa hay were 56 percent complete. Winter wheat was 1 percent planted. Pasture and range condition was rated 63 percent good to excellent, down from the previous week.

Field Observations Thru September 15

Corn

Growth & Development

Most of the corn that I have seen this week is in either the late R4 (Dough) or the R5 (Dent) growth stage.  A few fields are approaching the final growth stage R6.

R6 – Physiological Maturity

  • Occurs approximately 66‐70 days after silking.
  • R6 is reached  after the milk line disappears and the starch has reached the base of the kernel.
  • Kernels have reached maximum dry weight.
  • Kernel moisture is  about 35% at physiological maturity.
  • Black layer occurs after physiological maturity and  serves as a visual verification that the plant is mature. Black layer typically occurs at 30%  moisture but varies by hybrid and environment.
  • Husks and many of the leaves are no longer green, but the stalk may be green.
  • Only external stress can reduce yield now,  such as plant lodging or insect feeding.

Scouting

At this growth stage look for:

  • Ear rots.
  • Stalk rots.
  • Anthracnose top dieback.
  • Stalk lodging.
  • Abnormal ear fill which identifies periods of stress.
  • Weed escapes (especially Palmer and Waterhemp).

This is also a good time to get an accurate yield estimate.

Soybeans

Growth & Development

Soybeans are continuing to mature.  Last week I highlighted the R7 growth stage, the last growth stage is R8 full maturity.

R8 – Full Maturity

  • 95% of pods reached mature color
  • Mature pod color does not necessarily indicate that beans are ready to harvest
  • 35% grain moisture in freshly matured pod
  • 15% within another 5 to 10 days
  • Below-optimum plant stands cause more branching, low pod heights & can delay maturity
  • Above-optimum plant stands increase lodging.

Scouting

At this growth stage look for:

  • Green stem syndrome.
  • Lodging
  • Sprouting seeds
  • Pod shattering
  • Weed escapes (especially Palmer and Waterhemp).

This is also a good time to check soybean yield potential.

County Rainfall Update

Ohio Crop Progress

Source: USDA

Last week’s warm days and mostly fair weather supported crop progress but left some counties excessively dry, according to Ben Torrance, State Statistician, USDA NASS, Ohio Field Office. Topsoil moisture conditions were rated 9 percent very short, 19 percent short, 68 percent adequate, and 4 percent surplus. Statewide, the average temperature for the week ending on September 10 was 72.5 degrees, 4.6 degrees above normal. Weather stations recorded an average of 0.27 inches of precipitation, 0.27 inches below average. There were 5.6 days suitable for fieldwork during the week ending September 10.

Ninety-five percent of corn was in or past dough, 53 percent was in or past dent, and 11 percent was mature. Corn for silage was 27 percent harvested. Eight percent of soybeans were dropping leaves. Corn and soybean condition were 82 and 75 percent good to excellent, respectively. Third cuttings of alfalfa hay and other dry hay were 88 and 58 percent complete, respectively. Fourth cuttings of alfalfa hay were 38 percent complete. Pasture and range condition was rated 68 percent good to excellent, down from the previous week.

Field Observations Thru September 8

Corn

Growth & Development

Most of the corn that I have seen this week is in either the R4 (Dough) or the R5 growth stage.

R5 – Dent

  • The second to last stage of corn development.
  • R5 (dent) occurs approximately 31‐33 days after silking.
  • Kernels are dented in at the top with the “milk line” separating the liquid and
    solid (starch) portions.
  • Within R5, kernels are often staged according to the progression of the milk line; i.e. ¼, ½, and ¾.
  • At the beginning of R5, kernels have 60% moisture content.
  • Stresses will reduce kernel weight at this time.

Scouting

I have heard a wide range for projected corn yields this year.  The Yield Component Method is the most widely used procedure for estimating corn yield.  While  you are out checking potential corn yields, also keep an eye out for:

  • Ear rots.
  • Stalk rots.
  • Anthracnose top dieback.
  • Stalk lodging.
  • Abnormal ear fill which identifies periods of stress.
  • Weed escapes (especially palmer & waterhemp).

Soybeans

Growth & Development

Soybeans are continuing to mature.  Last week I highlighted the R6 growth stage  the next stage is R7 the last growth stage prior to maturity.

R7 – Begining Maturity

  • One mature-colored pod anywhere on the main stem.
  • Yellow pods are moving toward maturity.
  • Tan, brown or tawny pods (depending on variety) signal physiological maturity.
  • Seeds at the R7 growth stage are at approximately 60% moisture.

Scouting

  • Foliar diseases – Sudden Death Syndrome, White Mold, and Frogeye Leaf Spot.
  • Insect feeding – Grasshoppers.
  • Weed escapes (especially Palmer and Waterhemp).

Estimating soybean yields

It is much more difficult to accurately predict soybean yield.  The process to estimate soybean yields can be found here.

County Rainfall Update

Ohio Crop Progress

Source: USDA

Ninety percent of corn was in or past dough, 40 percent of Ohio corn was in or past dent, and 2 percent was mature. Corn for silage was 11 percent harvested. Ninetyfive percent of soybeans were setting pods and 3 percent were dropping leaves. Corn and soybean condition were 80 and 76 percent good to excellent, respectively. Second cuttings of other hay were 94 percent complete. Third cuttings of alfalfa hay and other dry hay were 75 and 51 percent complete, respectively. Fourth cuttings of alfalfa hay were 29 percent complete.

Estimating soybean yield

Soybeans are beginning to change color (mature) which has many of us thinking about yield potential.  To estimate soybean yield, four yield components need to be considered: plants per acre, pods per plant, seeds per pod, and seeds per pound (seed size).  A printable worksheet to estimate soybean yield can be found by clicking here.

Proceed with caution when estimating soybean yield. It is difficult to accurately predict soybean yield because of plant-to-plant variability and fall weather conditions can influence seed size.  Estimates are more accurate later in the growing season and on uniform stands.

To estimate soybean yield:

Step 1: To calculate plants per acre, count the number of pod-bearing plants in 1/1,000th of an acre.  In 7.5-inch row spacing, count the number of plants in 69 feet, 8 inches of row.  In 15-inch row spacing, count the number of plants in 34 feet, 10 inches of row.  In 30-inch row spacing, count the number of plants in 17 feet, 5 inches of row.

Step 2: To estimate pods per plant, count the number of pods (containing one or more seeds) from 10 plants selected at random.  Divide the total number of pods by 10 to get the average number of pods per plant.

Step 3: To estimate the number of seeds per pod, count the number of seeds from 10 pods selected at random.  Generally, the number of seeds per pod is 2.5, but this number can be less in stressful environmental conditions.  Divide the total number of seeds by 10 to get the average number of seeds per pod.

Step 4: To estimate the number of seeds per pound (seed size), assume that there are 3,000 seeds per pound.  If the soybean plants experienced stress, seed size will be reduced, and it will take more seeds to make one pound.  Use a seed size estimate of 3,500 seeds per pound if smaller seeds are expected because of late season stress.

Using the above estimates, the following formula can be used to estimate soybean yield in bushels per acre:  bushels per acre = [(plants/1,000th acre) x (pods/plant) x (seeds/pod)] ÷ [(seeds/pound) x 0.06]

 Example:110 plants per 1/1,000th acre, 65 pods per plant, 2.5 seeds per pod, 3,000 seeds per pound. [110 * 42 * 2.5] / [3,000 * 0.06] = 64.2 bushel per acre.