Why does maize lodge?

A healthy maize crop that receives enough nutrients during the season will seldom lodge. Invariably, individual plants that experience stress at some stage may show signs of lodging.

‘Lodging’ is the displacement of stems or roots from their vertical and proper placement. The two types of plant lodging can occur at the same time or separately, and both can reduce yield and nutrient density.

the mechanics of maize lodging

A maize plant needs carbohydrates produced by photosynthesis to fill the root and main stem cells and so keep the plant healthy. It also needs to store enough carbohydrates for the grain-filling stage.

If maize experiences stress at this stage, photosynthesis is reduced or even briefly stopped. This in turn reduces the amount of carbohydrates available for grain filling. The plant reacts by extracting stored carbohydrates from the leaves, stems and roots, and channels it to the developing kernels.

As can be imagined, the stems and roots suffer, and become vulnerable to fungal infection. Stalk borer damage and late autumnal rain can intensify the symptoms and the rate of infection.

A high nitrogen level, storm damage, soil density, disease, sowing date, overpopulation and seed type also contribute to lodging in a grain crop.

initial symptoms and infected lands

The first symptom is yellowing and deterioration of the lower leaves when the plant is almost physiologically mature.

Check for stem rot by flattening the internode between your thumb and forefinger. Alternatively, hold the cob and gently push it about 20cm towards the next row. If the plant bends or breaks between the head and the roots, stem rot and root rot are most likely present.

The presence of stem rot does not always cause maize to lodge, however. In addition, many maize hybrids have strong stalk walls that help the plant stay upright even when the stem core has been destroyed.

To avoid losses due to maize plants falling over, it is important to identify infected lands as soon as possible so that they can be harvested first.

• Source: Barnard, N. 2017. ‘Why does maize lodge?’ Grain SA. Retrieved from www.grainsa.co.za/ why-does-maize-lodge.

RL NIELSEN, PURDUE UNIVERSITY BELOW: Lodged maize can result in major financial loss. It’s important to identify the problem well in advance so that the plants can be harvested before they fall over.