Field Observations Thru July 21


Corn growth varies greatly throughout the county, but, more fields are beginning to tassel.  As corn begins to tassel, nutrient (K > N > P) and water (0.30 inch per day) demands for the crop are close to maximum. Heat and drought will affect potential number of kernels.  Scout for insects (e.g., corn leaf aphid, western bean cutworm, corn earworm, fall armyworm) and diseases (e.g., gray leaf spot, southern rust, northern leaf
blight). Total leaf defoliation severely affects final yields.

VT (Tasseling) – Stage VT occurs two to three days before silking, when the last branch of the tassel is completely visible but silks have not emerged yet from the ear shoot. The plant has reached full height and the pollen shed begins. The time between VT and R1 can vary with different hybrids and due to environmental conditions.
Pollen shed (pollen drop) normally occurs during the late morning or early evening. Hail damage is more serious at this time than for any other growth period. All leaves have emerged and the complete loss of a pollen source would result in no grain formation.

We are nearing a point in the growing season where it is time to scout your corn fields and make a decision regarding fungicide applications. Click here to view the 2023 corn fungicide ratings.


Postemergence herbicide applications – Don’t forget the preharvest intervals (PHI) for grazing or harvest. Read more here.


Soybean Postemergence Weed Control – Grasses

Soybean Postemergence Weed Control – Broadleaves

Soybean Growth & Development – R2: Full Bloom

  • Open flower at one of two uppermost main-stem nodes
  • About 50% of the total mature node number has been established.
  • Very rapid nitrogen (N), phosphorus (P), potassium (K) and dry-matter accumulation is occurring and will continue through R6.
  • Defoliation of the plant of 50% at this stage will reduce yield by 6%.
  • Approximately 60 days away from beginning of physiological maturity (R7).

County Rainfall Update

Mount Vernon, OH

Corn Water Requirements

Soybean Water Requirements

Farmer Sentiment Rebounds on More Optimistic View of Future

Source: James Mintert and Michael Langemeier, Purdue Center for Commercial Agriculture

Click here to listen to recap.

Farmer sentiment rebounded in June as the Purdue University-CME Group Ag Economy Barometer rose 17 points to a reading of 121. June’s sentiment improvement left the index near the April reading of 123 after a one-month swoon in May. The swing in sentiment was driven by producers’ more optimistic view of the future as the Index of Future Expectations rose 25 points to 123, while their perception of the current situation was unchanged. The Index of Current Conditions reading, at 116, was the same as in May. This month’s Ag Economy Barometer survey was conducted from June 12-16, 2023.

The contrast in producers’ perspectives on current conditions vs. future expectations was made clear when examining responses to individual questions in the June survey. When asked to compare their farm operation’s situation today with a year ago, 40% of respondents said their operation was “worse off” financially than a year earlier vs. 37% who felt that way in May while just 15% chose “better off” vs. 17% who made that choice in May. But when asked to look ahead one year, respondents’ attitudes changed. In June, 20% of respondents said they expected their financial condition to improve over the next year, compared to just 13% who said that in May. Meanwhile 32% expect their farm’s financial situation to decline over the upcoming year, compared to 44% who responded that way in May. Producers improved perspective on the future was not focused solely on their own farms, but extended to all of U.S. agriculture. The percentage of producers expecting good times for U.S. agriculture in the upcoming 5 years rose 8 points to 33% while the percentage expecting bad times fell 3 points to 41%.

Why are my soybeans yellow? Part 4

Soybeans throughout the county are beginning to look better.  Development has been slowed and many fields have areas (sometimes large areas) with a light green or yellowish tint to the beans.  What is causing this yellowing? One possibility is:

Nutrient Deficiencies


Caused many fields to turn yellow in late June and July.  A dry spring delayed nodulation, then heavy rainfall saturated soils just as plants required large amount of N during the rapid growth phase. There is often a lag phase when nodulation and N fixation is insufficient to supply enough N for the plants demands early in the season.
The good news is that most fields will recover as soils dry out and biological nitrogen fixation catches up to demand.
Some farmers have asked if N fertilizer could be added to these fields to help them through this yellow phase.  Although applying N fertilizer does help green up the plants there is no economic benefit.  Numerous trials conducted in Ontario, Canada  show the average yield response to N fertilization is less than two bushels per acre.

Reposted from Tim Barnes, OSU Extension Marion County July 16,2023


Potassium (K) deficiency symptoms are frequently seen on soybean at early development stages (starting as early as V3) but can also develop on plants throughout the growing season. Potassium deficiency symptoms include yellowing of leaf tissue starting at the leaf tip and moving down the leaf margin (outer edge of leaf) (Figure 1). Severe K deficiency can lead to pre-mature leaf fall of the older leaves.

Potassium deficiency symptoms are often more severe in years where root growth is slowed or delayed (wet or dry years) and can be observed in fields with adequate soil test K levels.  A poorly developed root system can limit nutrient uptake causing what is likely a temporary nutrient deficiency.   These deficiency symptoms often decrease or disappear once adequate root development and soil conditions improve.


Iron deficiency chlorosis (IDC) is most common in poorly drained areas of the field. Plants with IDC tend to be stunted and yellowing occurs between the leaf veins while veins remain green (interveinal chlorosis). Leaves may also develop brown and necrotic spots in leaf margins. Iron is an immobile nutrient, so these symptoms most often occur first on newer, upper leaves.

IDC  symptoms are more common in years where root growth is slowed or delayed (wet or dry years).  A poorly developed root system can limit nutrient uptake causing what is likely a temporary deficiency symptomology.   These deficiency symptoms often decrease or disappear once adequate root development and soil conditions improve.


Pest of the week – Soybean Aphids

Soybean Aphids

The soybean aphid, a native of Asia, has been in the Midwest since 2000 and has quickly become a serious pest of soybeans in parts of the Midwest.



Nymph: Nymphs look similar to wingless adult aphids but are smaller. White flakes may be present near aphids; these are cast skins from nymphs molting.

Adults: The soybean aphid is a small, yellow to green aphid with distinct black tailpipes, or cornicles, on the abdomen.


As with many aphids, the soybean aphid has a complicated life cycle, that requires the presence of its overwintering host, buckthorn. One important feature of the lifecycle is the ability of female soybean aphid to reproduce live, female offspring (clones) parthenogenically during the summer months. This means that soybean aphid numbers can often increase rapidly when conditions are favorable in a soybean field. Soybean aphid are usually found in soybeans from late May through August.

Sampling: Sample 20 plants from different locations throughout the field and count the number of aphids per plant.

Economic Threshold: The economic threshold for soybean aphid is 250 soybean aphids per plant, with an increasing population density. Thus, at least two samples are needed to determine whether the population size is rising. After the R5 growth stage there is no economic return to treating.

Management Options: There are several predators, including lady beetles, which may help take care of this aphid. If populations reach 250 aphids per plant and the density is rising, then the use of an insecticide might be needed. Resistant soybean varieties are now available that offer partial control of soybean aphid, although those fields should still be scouted. For more information, visit and

Impact in Knox County: Soybean aphids have rarely reached economic threshold levels in Knox County.  Could this be the year??  Click here to see the most recent information from OSU Entomologists Kelley Tilmon and Andy Michel.

Weed of the week – Pigweed

Redroot Pigweed

Family: Amaranthaceae

Lifecycle: Annual

Description: An erect summer annual that may reach 6 1/2 feet in height. Redroot pigweed is an abundant seed producer that may be found throughout the United States in horticultural, nursery, and agronomic crops, landscapes, roadsides, and also in pastures and forages.

Seedlings: Hairy, often red in color, especially near the base. Cotyledons are narrow and green to reddish in color on the upper surface. Lower surfaces of cotyledons have a reddish tint. First true leaves are alternate, ovate in shape, and are slightly notched at the tip of the leaf blade (apex). Hairs may occur on the leaf margins and along veins, especially along the lower leaf surfaces.

Roots: A shallow taproot that is often, but not always, reddish in color.

Stem: Stout, erect, branched, and reaching 6 1/2 feet in height. Stems usually have short hairs, especially near the upper portions of the plant.


Leaves: Alternate, ovate in outline, with petioles that reach 1/2 inch in length. Leaves have wavy margins and hairs that occur along the veins of the lower leaf surfaces.



Flowers: Small, green, inconspicuous flowers are produced in dense, compact, terminal panicles that are approximately 3/4 inch wide and from 2 to 8 inches in length. Smaller inflorescences also occur between the stem and the leaf petioles (leaf axils). Male and female flowers occur on the same plant (monoecious). Each terminal panicle contains many densely packed branched spikes that have bracts that are 4 to 8 mm long and 2-3 times longer than the sepals.

Special identifying characteristics: Dense, compact terminal panicles and relatively tall plants with alternately arranged leaves. Redroot pigweed is often confused with other similar pigweed species. For example, Smooth Pigweed (Amaranthus hybridus) is very similar, however this species has terminal panicles that appear less dense, compact, and bristly than those of redroot pigweed. Additionally, the bracts of smooth pigweed are only slightly longer than the sepals, unlike those of Redroot Pigweed (Amaranthus retroflexus). Palmer Amaranth (Amaranthus palmeri) also resembles redroot and smooth pigweed, however the terminal panicles of this species are much longer and narrower than the other pigweed species. These species may also resemble Common Lambsquarters (Chenopodium album) in the cotyledon stage, however common lambsquarters cotyledons often have a mealy gray cast, and the first true leaves are alternate, unlike any of the pigweed species.

Click here to watch pigweed ID video


Why are my soybeans yellow? Part 3

Soybeans throughout the county are beginning to look better.  Development has been slowed and many fields have areas (sometimes large areas) with a light green or yellowish tint to the beans.  What is causing this yellowing? One possibility is:

Too much water/waterlogged roots

In some fields, the pale green to yellow leaves are the result of very wet soil conditions. Soybeans are a legume (like alfalfa) and do not like wet feet (roots)! This problem is commonly seen in low areas of the field or on poorly drained soils where water tends to stay for a prolonged period of time. When digging up plants in wet areas of the field you will find poorly developed or weaker root systems when compared to a healthy plant.

Soil water content is critical not only to supply the water needs of the plant, but to also dissolve nutrients and make them available to the plant. A poorly developed root system can limit nutrient uptake causing what is likely a temporary nutrient deficiency.

Temporary nutrient deficiencies can be observed when excess water in the soil depletes oxygen and builds up carbon dioxide levels. Although oxygen is needed by roots to grow and take up nutrients, high carbon dioxide levels are toxic and limit root growth and activity.

With better weather conditions plants will usually (sometimes slowly) grow through this phase.

Soybean nutrient deficiencies will be discussed in a different post.

Preharvest Intervals for Soybean Herbicides Applied Postemergence

Preharvest intervals indicate the amount of time that must elapse between the herbicide application and crop harvest. Failure to observe the preharvest interval may result in herbicide residue levels in the harvested portion of the crop in excess of established limits. Also, livestock grazing or foraging treated soybean is not allowed on the labels of many postemergence soybean herbicides. Table 1 contains information regarding preharvest intervals and grazing restrictions for a number of postemergence soybean herbicides.

Table 18 from the OSU Weed Control Guide shows the PHI and feeding restrictions for postemergence soybean herbicide applications.

Benchmarking Crop Machinery Cost And Investment

by Michael Langemeier, Purdue University

The continued increase in size of tractors, combines, and other machinery has enabled farms to operate more acres and reduce labor use per acre. However, this increase in machinery size also makes it increasingly important to evaluate the efficient use of machinery. This article will discuss machinery cost and investment benchmarks, and illustrate the computation of crop machinery cost and investment for a case farm in west central Indiana.

Key Machinery Benchmarks
Crop machinery cost per acre is computed by summing depreciation, interest, property taxes, insurance, leasing, repairs, fuel and lubricants, and custom hire and rental expense; and dividing the resulting figure by crop acres or harvested acres. Interest should include both cash interest paid and an opportunity charge on machinery and equipment that is owned. In regions where double-cropping predominates, using harvested acres is preferable.

Crop machinery investment per acre is computed by dividing total crop machinery investment (i.e., investment in tractors, combines, and other machinery) by crop acres or harvested acres. Again, in regions where double-cropping is prevalent, using harvested acres gives a more accurate depiction of machinery investment.

Machinery investment per acre typically declines with farm size. Thus, it is important for farms to compare machinery investment per acre with similarly sized farms and to examine the trend in this benchmark for a particular farm. A farm with relatively high machinery investment per acre needs to determine whether this high value is a problem. If the farm faces serious labor or timeliness constraints, their machinery investment per acre may be relatively high. However, if their machinery investment per acre is high due to the purchase of assets used to mitigate income tax obligations or for some other reason, the farm needs to think about their long-term strategy with respect to purchasing machinery and equipment.

Click here to read the entire article.