Most customers in the Hoegemeyer footprint received some much-needed rain over the last several days. Many areas of Nebraska received a nice, gentle rain, totaling between 1 and 4 inches, but a good portion of central Nebraska received totals in excess of 6 inches. Producers have been calling, asking, “How long will my newly emerging crop survive being ponded or flooded?” Here are some guidelines taken from the University of Nebraska-Lincoln Extension.
Small seedlings will be more susceptible to flooding and ponding than larger plants. The smaller the plant stature, the better chance of it being covered with silt, getting mud in the whorl (which can lead to both fungal and bacterial pathogens causing stand loss), or just not having the ability to respire. Germinating seeds are living organisms and require oxygen to survive. Oxygen levels in fully submerged soils will be down to zero after 48 hours. Cooler air temperatures could help, as we are experiencing now, but it is unlikely that any seed, emerged or not, will be able to survive more than four days under water. Larger seedlings could survive up to four days in saturated conditions if air temperature is below 80 degrees Fahrenheit (See Table 1). If temperatures get into the 90s, corn seedlings may only survive for 24 hours.
Soybeans will share a similar fate to corn. Soybeans that have been submerged for two days will likely experience stand losses of 20 to 40%, depending on conditions after the flooding or if ponding subsides. Soybeans that are submerged for more than two days will likely need to be replanted.
If you feel you may need to replant, or have unexpected stand loss, don't hesitate to reach out to your local Hoegemeyer representative so we can help evaluate options. Hoegemeyer also offers free replant to Hoegemeyer corn customers who are part of the loyalty club, and free replant for any customer using Hoegemeyer brand LumiGEN soybean seed treatment. Evaluating and resolving these issues as early as possible will get you on track to having the best opportunity for a successful crop.
Early frost damage is a concern for growers throughout the Western Corn Belt each Spring with the unpredictability of Midwest weather. After the freezing temperatures we experienced last weekend, determining the level of frost damage to plants is important for producers. With many of our producers finishing up planting, we understand the importance of knowing how the freeze impacts your plants.
Some plants will recover from early frost, however depending on the damage, some may need replanting. Corn can survive a frost if a seedling’s growing point is not affected.
What steps should you take after a frost?
Analyze the frost damage – Frozen leaves will turn silver in the first few hours after temperatures return to normal. Leaf tissue becomes dark and water-soaked, then brown and dry. New leaves will typically emerge within 3-4 days if the growing point is unharmed.
Patience. Patience. Patience. Waiting for new growth to emerge is necessary to make a final decision on potential harm done to the crop.
Decide if replanting is required – After 3-4 days, the extent of damage can be better determined. To accurately establish an estimate of the damage, check out plants from three different parts of the field.
Corn seedlings can handle frost much better than soybean seedlings. The growing point of corn doesn’t emerge from the soil surface until V5-V6 stages. Soybeans growing point is located above the cotyledon; but has risk of frost damage as the cotyledons are emerging through the soil. Below is a picture of a soybeans plant structures. Notice the growing point just above the Unifoliate leaf.
Soybean replant decisions should be based on accurate stand count and interacting factors, including yield potential of the existing stand, planting date, maturity group, and the true cost of replanting. Unfortunately, producers tend to make replant decisions based on quick visual estimations that often underestimate the existing plant population. Seedlings are usually in an early vegetative growth stage with only a few leaves when early stand counts are made. Narrow row widths exaggerate the impression of a low stand level because there are larger within-row spaces between plants.
When we talk about early season soybean diseases, we are referencing soybean root pathogens that can affect the health of the plant early on in its growth from first imbibition - the seed’s first taste of moisture, to germination, through emergence and the early vegetative stages of the plant.
There are four major pathogenic fungi that can be hazardous to a young soybean causing seed rot, seedling mortality, and root and stem decay. These pathogens are Pythium, Fusarium, Rhizoctonia, and Phytophthora. While most early season soybean diseases do occur in cool and wet soils, some pathogens thrive in warm and dry soil conditions.
Both Pythium and Fusarium are more active in cooler and wetter environments. Pythium is most likely to occur in moist soils with temperatures ranging from 50-59°F (Pythium ultimum*). One of the more common species of Fusarium is most active in moist soils with temperatures ranging from 57-73°F (Fusarium oxysporum sp.*).
On the other end of the spectrum, Rhizoctonia and Phytophthora are two pathogens that tend to prefer warmer soils. One strain of Rhizoctonia (Rhizoctonia solani*) is most detrimental to soybeans when soil temperatures are in the 77-85°F range and can be active in dry soil conditions. The fourth major pathogen in this group, Phytophthora, is one of the leading yield robbing pathogens in soybeans and is most active in warmer soil environments ranging from 77-86°F (Phytophthora sojae*).
Your crop’s highest potential starts with the seed. Good planting practices that minimize stress and the use of seed applied fungicides are the best ways of managing early season soybean diseases. Once the seed is in the ground, not much can be done to defend against them.
Hoegemeyer’s LumiGEN™ seed treatment provides a comprehensive portfolio with industry-leading and proven fungicide components to protect against all these pathogenic fungi. Protect your seed’s potential and your bottom line by protecting your crop with LumiGEN.
Soil temperatures identified in the Compendium of Soybean Diseases, 3rd Edition.
The optimal temperature for corn emergence is in the range of 80° to 90° Fahrenheit. Emergence is greatly reduced at lower temperatures and is effectively halted around 50° to 55° Fahrenheit or below. Since soil temperatures in the early season are almost never optimal, emerging seeds will experience a degree of stress. The degree of stress, and potential damage from stress is determined mostly by soil and water temperatures during imbibition and seedling emergence.
For successful emergence to occur, all parts of the shoot (roots, mesocotyl, coleoptile and leaf within) must work in a coordinated way to push the coleoptile above the soil surface and allow the first leaf to unfurl. Damage to any one of these structures will likely result in loss of the seedling and its yield potential.
The Critical First Hours
When the dry seed imbibes cold water (typically 50° F or below), imbibitional chilling injury may result. The degree of damage ranges from seed death to abnormalities such as corkscrews or fused coleoptiles.
The potential for cold-water damage generally decreases as the seedlings emerge. It also decreases if the initial imbibition takes place at temperatures above 50° F. This may help explain observations where early-planted corn, which was followed by favorable weather, emerged better than corn planted later and followed by a cold spell.
Damage to the emerging root usually has less severe consequences on seedling survival. This is because the primary root, which is the first structure to emerge, plays a relatively minor role in seedling establishment compared to the lateral and nodal roots. Seedling establishment can usually progress normally if the lateral and nodal roots are intact. Any damage to the roots, however, will likely reduce vigor and increase the potential for disease and insect injury.
Seedling Disease and Stress Emergence
Stress emergence is an agronomic trait intended to reflect genetic variability for tolerance to abiotic stress in the early season. It is not a rating for disease resistance. Early-season stress can promote seedling disease if certain conditions are met, including inoculum presence and prolonged cool, wet conditions. Injury to emerging seedlings will also promote seedling disease. Injury can be caused by chilling, such as imbibitional damage, or by feeding of insects such as seedcorn maggots, white grubs and wireworms.
In environments with heavy inoculum pressure, disease progression is often in a race with seedling growth. Conditions that promote rapid soil warming will generally favor seedling growth and reduce disease incidence. On the other hand, extended cool, wet conditions will generally favor disease progression.
Many soil pathogens, including some Pythium species, are most active at temperatures in the 40s and 50s (F). Low temperatures such as these can injure emerging seedlings and facilitate infection. Low temperatures also retard stand establishment and increase the window of vulnerability to infection. Seed treatment fungicides generally provide good efficacy against target organisms for 10 to 14 days after planting. However, protection will be diminished if emergence and stand establishment are delayed beyond this period.
Successful stand establishment requires understanding and managing risks. Early-season damage is difficult to diagnose since most of it occurs before the crop emerges. The best management strategy is to understand the conditions and environmental factors that can cause stand reduction and to minimize exposure to these adverse environments.
Deciding when to plant is probably the factor with the largest single impact on stand establishment. The risk of damage to emergence is greatest if the crop is planted into very cold soil or if planting is followed by severe cold weather. Often, planting date is dictated by workload and field conditions. If a cold spell is expected after planting, it is advisable to plant fields with better drainage and less residue first. Choosing hybrids with strong stress emergence helps reduce genetic vulnerability to stress, and planting seeds with a premium seed treatment helps provide critical protection in stressful environments where seeds are vulnerable to attack.
-Stuart Carlson, Northern Region Product Agronomist
Every year established alfalfa stands have the potential for winter injury and winter kill. We have had a mild winter with some cold temperatures and some above freezing temperatures. However, the lack of snow cover is one of the main issues producers are worried about as the assess their alfalfa stands this spring.
What could have caused my alfalfa plants to winter kill?
Stand age: Older stands are more likely to winter kill than younger plants.
Snow cover: Snow provides insulation to the plants and the crown. The crucial temperature region is two to four inches below the soil surface where a large part of the root structure is located. Stands that have at lease six inches of stubble left will be able to retain more snow cover and be less likely to winter injury.
Soil pH: Soils with a pH above 6.6 are less likely to experience winter injury.
Cutting management: Aggressive harvest schedules and shorter intervals between cuttings leave the alfalfa less time to accumulate carbohydrate levels in the root system before winter. This leaves the alfalfa plants more likely to winter injury.
Soil fertility: Stands planted in higher fertility soils are less likely to experience winter injury than those with low fertility.
When you are scouting your alfalfa stands look for these symptoms to assess if your field winter killed:
Compare you stand to other fields in the area. If you have spots that are greening up nicely and spots that are brown, it is time to check those brown stands for injury or death.
Winter killed roots will have a gray appearance. Check if the roots are soft and brown in color, these are signs that your stand has winter injury.
Compare the shoots on the same plant, and if you notice that one set of shoots seems to be drastically out-growing others in terms of growth, the bud could be damaged from winter injury.
Evaluation of your alfalfa stand in the spring can be tricky. I have learned that “patience is a virtue” is a phrase that applies well when scouting and making decisions on your field. Deciding to rotate out of alfalfa or inter-seeding into an established alfalfa fields can be a hard decision. If you have any questions while you are evaluating your alfalfa stand this spring, give your product agronomist a call.