C.O.R.N. Newsletter: 2025-30

Season 3, Episode 23 of Battle for the Belt is now available: https://www.youtube.com/watch?v=vPUcULGy-h8

At this stage of the growing season, soybean fields may commonly exhibit foliar yellowing. While such symptoms can be associated with the onset of physiological maturity, they may also indicate the presence of disease. Therefore, regular field scouting remains a critical practice for accurate diagnosis.

One of the most frequently observed diseases during this period is Sudden Death Syndrome (SDS), which produces characteristic foliar interveinal chlorosis and necrosis (Figure 1). Recently, Red Crown Rot (RCR) has been confirmed in Ohio (Figure 2). This is of particular concern because the foliar symptoms of RCR are nearly indistinguishable from those of SDS, complicating field-level identification. To correctly differentiate between these two pathogens, root and crown examinations are required. In cases of red crown rot, the basal stem and crown tissues typically exhibit a distinct reddish to orange discoloration, which serves as a diagnostic feature of the disease. Read and learn more about red crown rot here.

Remember, when scouting your soybean field and if you identify red crown rot symptoms you should submit whole soybean plants with their root systems to the CFAES Soybean Pathology and Nematology Laboratory. Address samples to Horacio Lopez-Nicora, 110 Kottman Hall, 2021 Coffey Road, Columbus, OH 43210. Detailed instructions for sample submission are provided here.

What’s happening in the field?

 Drought conditions continue to be present and expand across the state, with very little rainfall occurring in recent weeks (Figure 3). As a result, several counties went from D0 (abnormally dry) to D1 level (moderate drought).

Many of our corn and soybean plants across planting dates are now in critical grain-filling stages, which can be sensitive to drought stress. In corn, drought during these stages can lead to premature death of leaf tissue, shortened grain-fill periods, kernel abortion, and reduced kernel weight compared to crops under more favorable moisture conditions. When drought occurs during the later reproductive stages, specifically R4 (dough) and R5 (dent), it often results in lighter kernels and can cause premature physiological maturity.

Soybeans are generally more resilient than corn under drought conditions, but prolonged dryness during pod set and seed fill still presents risks. When moisture is limited during these stages, the plant’s ability to compensate is reduced. This typically results in fewer seeds per pod, smaller seed size, and earlier maturity. Similar to corn, drought shortens the grain-filling period, and the greatest yield losses in soybeans are usually seen when drought occurs between the R4 (full pod) and R6 (full seed) stages.

 Field observations show that crops are continuing to progress steadily toward maturity. At the Western location, corn from planting date one has dried down quite a bit and is the first to reach the R6 stage, which marks physiological maturity (Figure 4). Corn at the Northwest and Wooster sites is not far behind, as it continues to dry down. In soybean, planting dates one through four have reached the R6 stage, full seed. These plants will enter R7 (begin maturity), once at least one pod on the main stem has turned brown or tan. For further information regarding weather summaries and crop growth stages, see Table 1.

Keep following the ‘Battle for the Belt’ this growing season to learn more and get further updates! You can find the full video playlist of Battle for the Belt on the Ohio State Agronomy YouTube channel.

Timing of your last cutting is one of the most important factors for maintaining alfalfa persistence over winter. The Ohio Agronomy Guide recommends that cutting finishes by Sept 7 for northern Ohio and Sept 15 for southern Ohio—these recommendations are based on the amount of time it typically takes for alfalfa to regrow to ~8 inches before a ‘killing’ frost occurs, stopping growth for the year.

What’s the value of fall regrowth?

Fall regrowth ensures the plant has sufficient sugars and carbohydrates in the root system, which is critical for winter survival. The biomass of plants above ground also helps protect the crown against harsh winter weather by helping to hold onto snow, which can help insulate plants from the drying effect of cold winds. Plant material also helps cover the soil surface, which can reduce the intensity of rapid freeze-thaw cycles that contribute to frost heave.  Taking a fall harvest will provide feed this year, but often at the expense of next year's spring yield.

Why is timing fall harvest particularly important this year?

Even though the taproot of alfalfa can continue growth during short-term dry weather, its growth is reduced by longer-term dry conditions. The drought monitor for our region indicates that much of the state is currently classified as D0, and forecasts indicate that the dry weather will persist for at least another week. This will reduce the recovery growth of alfalfa going into winter, increasing the risk that late-cut alfalfa may not regrow sufficiently before hard frosts.

If you need more feed for the winter, when should you harvest? 

The best harvest option for more feed is after the fall rest period, when the alfalfa has undergone winterization. Winterization correlates to cutting after a killing freeze (23-24°F for several hours), after which the plant is dormant. This is not as stressful to the plants as cutting during winterization and can be a viable option for those who need feed and do not want to risk next year’s stand. However, remember that you should leave 5-6” of stubble, which leaves some plant tissue and helps to reduce erosion and provide some insulation during freezing and thawing cycles. The freeze-thaw risk is most significant on poorly drained soil. As dry conditions persist, your best options if feed is needed will be to harvest corn as corn silage or consider alternative feeds such as corn grain and corn stalks. 

How does soil fertility impact alfalfa fall management?

Potassium (K) is critical to alfalfa growth and enhances cold tolerance during winter . Physiologically, K is needed for plants to regulate water; if K levels are too low, plants will be at greater risk of winterkill and especially desiccation-related winterkill. In fields with low soil test K (STK below 120-170 ppm for agronomic crops in Ohio, when analyzed via Mehlich-3 extraction), applying potash a few weeks before growth stops for winter allows fertilizer to enter the soil profile and begin being taken up by plants.

Even in fields with high levels of soil test K (STK), potassium uptake may have been reduced this summer and fall due to low water availability. While low water availability impacts uptake of all nutrients, K uptake is particularly sensitive to dry conditions due to interactions between K and clay particles. Currently, we do not have evidence for management options that consistently improve K uptake during fall drought.   

Further Reading:

Ohio Agronomy Guide, 16^th Edition. https://extensionpubs.osu.edu/ohio-agronomy-guide-16th-edition/

Tri-State Fertilizer Recommendations for Corn, Soybean, Wheat, and Alfalfa. https://extensionpubs.osu.edu/tri-state-fertilizer-recommendations-for-corn-soybean-wheat-and-alfalfa-pdf/?searchid=0&search_query=974