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USCP Agronomy Check
A column by a Sorghum Checkoff agronomist.
BRENT BEAN
LUBBOCK, TEXAS
Lodging can occur with any plant, but unfortunately occurs in sorghum more than any of us would want. Some years are worse than others, and in 2015 we saw more lodging in sorghum than in the previous few years. There are two types of lodging – root lodging and stalk lodging.
Root lodging
Root lodging is when the stalk is intact but the plants lodge from the roots. The roots either break off or pull loose from the soil causing the plant to fall over. When this occurs early in the life of the plant, sorghum will usually recover, although a “bend” in the stalk will remain, which is called “goosenecking.”
Root lodging can occur on small plants from two to three weeks after emergence to any time prior to harvest. When it occurs early, the final yield is generally not affected since the plants quickly begin to grow upright. Root lodging predominantly occurs when soil conditions are wet and very high winds occur. When sorghum is irrigated, growers should allow the soil to dry between irrigations the first 35 days after planting to encourage the roots to develop deeper into the soil.
Insect feeding on roots also can greatly increase lodging, so seed treatments should be considered.
Stalk lodging
Stalk lodging is when the plant stalk either breaks or bends over and does not recover. This can occur either at the base or higher up on the plant stalk. There are several causes of stalk lodging:
• High wind speeds.
• Genetics. Some hybrids will lodge more than others will. Growers should take the opportunity to review hybrid standability ratings from the 2015 season.
• Lignin content of the hybrid. It has long been known that lower lignin content is highly correlated to lodging.
• Plant population. Higher plant populations result in increased lodging potential.
• Narrow row spacing tends to cause stalks to be smaller in diameter.
• Stalk borers and diseases.
• Sugarcane aphid. Left untreated, sugarcane aphids take away valuable nutrients from the sorghum plant causing stress that can lead to an increase in lodging.
• High soil N levels. High N levels are known to promote lodging.
• Low soil K levels. K is necessary for normal lignin and cellulose development in plants, enabling them to stand upright and resist lodging.
• Stresses during grain fill. When sorghum is stressed from lack of water or nutrients during grain fill, starch reserves in the stalk are transported to the grain. This weakens the stalk, predisposing it to lodging.
• High grain yield. In and of itself, high grain yield does not cause lodging, however, when other issues are affecting stalk strength, it adds weight to the top of the plant creating more stress on the stalks.
What can you do?
• Evaluate hybrids for standability, charcoal rot and fusarium.
• Apply only the amount of nitrogen needed to meet the desired yield goal. This is seldom a problem since most growers under-apply N in sorghum.
• Check soil potassium levels and correct if needed.
• Do not plant more seed than is needed to reach the desired yield goal. ∆
BRENT BEAN: Agronomist for Sorghum Checkoff
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