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What is lodging?
Impact of lodging
Wind acts on the shoots to create a leverage force, the size of which is determined by wind speed, area of the ear and height of the crop. When this force exceeds the strength of the stem base then stem lodging occurs (Figure 1). The strength of the stem base is determined by the diameter, wall width and the strength of the stem wall material.
When the leverage exerted by all of the shoots belonging to a plant exceeds the strength of its anchorage system then root lodging occurs (Figure 2). The strength of the anchorage system is determined by the spread of the root plate and the strength of the surrounding soil.
Soil strength is critical for root lodging and it is affected most by rainfall, but also by soil type and cultivations. Just 7mm of rain is sufficient to wet up the soil to 40mm – the average depth of the anchorage roots – and this weakens the soil strength several-fold.
Varietal choice has a major influence on lodging risk. The HGCA Recommended Lists give a lodging resistance score for each variety which ranges from 1 (very susceptible) to 9 (very resistant). In practice, a score below 3 is too susceptible to be grown commercially.
Varieties are often more prone to one form of lodging than the other. However, the current varietal lodging resistance scores represent an average risk to stem and root lodging.
A severe infection of eyespot (lesions girdling more than half the circumference of the stem causing stem softening) reduced stem strength by 46% and reduced the stem lodging resistance score by three points. Take-all is unlikely to increase lodging risk because the reduction in yield and shoot leverage outweighs any reduction in anchorage strength.
How to avoid lodging