Navigating Spring Freeze Challenges: A Guide for Wheat Farmers in Western Kansas

When and Where Spring Freeze Injury Occurs:

Spring freeze injury occurs when low temperatures coincide with sensitive plant growth stages, affecting either large areas or specific fields. The risk is heightened in low-lying areas such as rivers, valleys, and depressions where cold air tends to settle. The probability of spring freeze injury increases when wheat initiates spring growth early due to higher temperatures and inadequate moisture, advancing through developmental stages quicker than usual.

Early-maturing wheat faces a higher risk of injury than its late-maturing counterparts. The susceptibility to freezing temperatures increases as wheat matures during spring. While varietal differences in resistance exist, they are primarily linked to growth stages, making it challenging to enhance freezing resistance in improved varieties.

Temperatures that Cause Spring Freeze Injury:

After winter hardening, wheat loses its resistance to freezing when growth resumes in the spring. The most sensitive period to freeze injury is during reproductive growth, particularly during late boot or heading stages. Even slightly below-freezing temperatures can severely damage wheat at these stages, significantly reducing grain yields.

The severity of injury depends on the duration of exposure to low temperatures, with prolonged exposure causing more significant damage. Temperatures leading to injury are indicated in Figure 1 below (Figure from the KSRE Publication C646 Spring Freeze Injury to Wheat), with the influence of various factors making it difficult to predict the extent of injury accurately.

Symptoms of Spring Freeze Injury:

Recognizing the symptoms of freeze injury is crucial for early assessment and decision-making. Symptoms vary at different growth stages:

• Tillering Stage:
  • Leaves become twisted, light green to yellow, and necrotic at the tip.
  • Growth slows, potentially reducing tiller numbers.
• Jointing Stage:
  • Growing points become off-white or brown, with chlorotic or dead leaves.
  • Stem injury may result in lodging or lesions.
• Boot Stage:
  • Spikes may be trapped inside boots or emerge abnormally.
  • Anthers in spikes may turn white or yellow, indicating freeze injury.
• Heading Stage:
  • Awns may bleach to white, and a frost ring may appear on stems.
  • Sterility, leaf desiccation, and lesions on lower stems may occur.
• Flowering (Anthesis) Stage:
  • Freezing kills male parts, leading to sterility.
  • Anthers become white and shriveled.
• Milk Stage:
  •    – Developing kernels may fail to reach full size or appear shriveled.
  •    – Kernels may be gray and liquid instead of white and viscous.
• Dough Stage:
  • Kernels may have an unsightly, wrinkled appearance.
  • Germination may be slightly reduced.

Management of Freeze-Injured Wheat:

After assessing the extent of freeze injury, growers have several options for managing damaged wheat. One crucial consideration is whether the damage is partial or widespread, impacting only specific areas or entire fields. In cases of partial injury, where alternative management practices might disrupt established rotation systems or when suitable alternatives are unavailable, exercising patience is often the best approach. Despite the potential lodging caused by lower stem damage and increased shattering losses, wheat that has been injured can often yield enough to offset harvesting and hauling costs.

However, it’s important to note that grain quality may be compromised, especially when injury occurs after the flowering stage. Wheat grains may have lower test weights, appear shriveled or discolored, and exhibit a mix of kernels of different sizes and maturities. While such grain may not be ideal for making bread, it can serve as excellent cattle feed due to its high protein content. When incorporating freeze-injured wheat into livestock rations, a gradual approach over one week is recommended, with the proportion not exceeding one-third to one-half of the total grain in the ration.

For those considering using grain from freeze-injured plants as seed, germination checks are crucial before planting. Most wheat varieties exhibit natural dormancy, causing low germination rates for several weeks after harvest. Cold treatment or delayed germination tests are advisable in such cases. Shriveled seeds, even with high germination percentages, should be avoided as they result in poor field emergence.

Conditioning the grain can improve its suitability for use as seed, particularly if the freeze injury is widespread. This process involves removing small, shriveled, or immature kernels, leaving behind the largest kernels and raising the test weight to acceptable levels. The severity of conditioning depends on the extent of freeze injury, and germination tests should be conducted after conditioning and any storage period. Properly conditioned seeds can maintain a high germination level for one year if stored under suitable conditions.

Alternatively, if forage is needed or can be marketed, cutting freeze-injured wheat for hay or ensilage can be an economical and practical choice. The feeding quality of hay or ensilage remains good until the soft dough stage. Cutting and removing the wheat vegetation can prevent it from becoming a weed if the land is replanted to other crops. However, it’s essential to check the nitrate content of the forage to avoid toxicity to livestock.

Alternative crops are another viable option after early assessment of spring freeze injury. Sorghum could be a choice for western Kansas. Sunflowers or corn may also be considered if the soil profile has sufficient moisture or irrigation is available. Suppose growers do decide to terminate a damaged crop in favor of an alternative. In that case, it’s crucial to use herbicide or tillage to kill freeze-injured wheat if it is not cut for forage, preventing it from becoming a weed in replanted crops.

Before destroying damaged wheat and opting for another crop, growers must carefully weigh the production costs incurred so far, excluding harvesting and hauling. Replanting involves its own production and fixed costs, and the return on the new crop over its production costs must exceed the value of the damaged wheat over-harvesting and hauling costs to make it a worthwhile investment.

Interested in learning more? Download the KSRE Publication Spring Freeze Injury to Kansas Wheat visuals of freeze damage signs and more information.