Primary symptoms

Plants flattened. If lodging before flowering, then plants may recover and grow upwards. Lodging can reduce yields and increase diseases.

When lodging occurs before flowering, the plant can often recover and yield is not seriously affected.

Summary

Lodging is when the crop falls over. A normal vertical crop is finely balanced, so anything that upsets the balance will cause it to lodge: strong winds, heavy rain, a very wet soil during late grain filling, tall thin stems that bend, root or stem rots that weaken the plant base. Winds associated with excess water are the worst combination.

Lodging destroys the canopy structure. Solar radiation is no longer intercepted efficiently with high light to young upper leaves and low light to old leaves. Heads are covered in the tangle and the collapsed crop becomes more susceptible to pests and diseases.

Lodging during early stem elongation has a relatively small effect on yield as the crop will right itself and reform the canopy. The stem nodes alter the angle of extension making new growth vertical (see the nodes in the centre of the above photo).

From anthesis onwards the effects of lodging are large. For every day that the crop is lodged yield declines by more than 1% (Stapper and Fischer 1990). So for crops severely lodged shortly after anthesis and remaining so, final yield will be less than half that of the upright crop.

Any lodging also makes harvesting more difficult and increases the likelihood of losing grain during harvesting.

Has your crop fallen over?

• What percentage of the field is lodged? 10%, 50%, the whole field?
• Was lodging early or late? You will probably be able to tell by the extent to which the stems have righted themselves. Yield loss will be minor if lodging was during early stem elongation.
• Look closely for disease on the stems. Are the lower internodes light brown with necrotic eye-shaped patches? This is probably the foot rot eyespot (Pseudocercosporella herpotrichoides) that eventually rots through the stem.
• Look at each lodged area and estimate the average angle of lodging. That is, how far have the stems fallen from the vertical. In the photo the worst lodged stems have fallen about 60° from the vertical. Calculate a lodging score for the field by dividing the angle of lodging by 90 (e.g. 60°/90), then multiply that by your estimate of the area of the field affected (say 10%=10/100). Multiply that lodging score by the number of days the crop is lodged for lodging duration. Yield falls by 1% for every 2 units of lodging duration at the grain milk stage.

Why has the crop fallen over?

• There were high winds and heavy rain after stem extension began or it was windy while irrigations were in progress during grain filling.
• Excess nitrogen was applied resulting in too much top growth and top-heavy plants. Are other farmers having similar problems with different varieties?
• A tall, unimproved variety was used, unsuited to high nitrogen nutrition.
• Eyespot, root or crown rots weakened the stem or base of the plant.
• Low potassium availability.
• The seed rate was too high, preventing tillering and resulting in weak stems.
• Machinery or animals in the crop caused physical damage.

What you can do to stop it falling over

• Irrigation timing: Do not irrigate when you expect winds. Irrigate in late afternoon when winds tend to subside, or early morning if that is the calmest time of day in your area. Particularly avoid irrigating if high winds are forecast. The yield loss associated with extensive lodging is greater than a day of water stress.
• Late irrigation: Avoid over wetting the soil during late grain filling.
• Variety: Change to a shorter variety if your area is prone to high winds or rainstorms during the later stages of growth.
• Nitrogen: Reduce nitrogen applications to unimproved, tall varieties, particularly very late applications. Split your nitrogen applications between planting and first node (Z3.1).
• Plant density: Reduce seeding density (see optimum seed rate) and/or planting depth to encourage early tillering and crown root production. This can give plants a stronger base.
• Diseases: Control crown and root diseases by appropriate agronomy and/or seed dressings. Spray at Z3.0 if there are signs of eyespot.
• Potassium: Use a potassium fertilizer.
• Raised beds: Adopt the raised bed planting system. Irrigation in this system does not wet the soil around the base of the plant to the same extent as flat plantings.
• Fencing and machinery: Check fencing to ensure animals are kept out and use machinery carefully.