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Lodging in Small Grains and Corn (07/30/20)

I have heard many reports of the small grain crops in North Dakota being shorter than normal this year. In most of my own experimental plots, they are indeed notably shorter than normal.

Small grains-

I have heard many reports of the small grain crops in North Dakota being shorter than normal this year. In most of my own experimental plots, they are indeed notably shorter than normal. Shortened plant height this year is probably associated with stress (most likely heat stress in the case of my research plots) during key developmental processes that affect stem elongation. Therefore, it is somewhat surprising to see lodging in small grains already this season (see Figure 1). The recent unsettled weather that brought heavy rain and strong winds, no doubt was the reason that even a relatively short crop lodged. Lodging can significantly impact yield and even if yield is only slightly reduced, severe lodging almost always negatively impacts grain quality and makes harvesting a challenge.

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Lodging is the term used to describe a crop when its stems have partially or completely fallen over from their normal near vertical orientation. There are two types of lodging in small grains. Root lodging is lodging that occurs at the base of the plant as a result of roots failing to anchor the plant. Root lodging is the most common of the two types and is the type that occurs earlier in the season. Stem lodging occurs when the stem breaks. Stem lodging can occur at any point in the stem, but most commonly occurs at the lower portion of the plant and usually later in the season as the plant begins to mature and stems become brittle. Stem sawfly can cause lodging as it notches stem when it matures. There have been reports of sawfly in non-traditional areas, so check plants within a field with stem lodging for feeding injury near the base of the plant to confirm if the sawfly might be the reason the lodging. When root lodging occurs early (before grain filling), it is possible for some stems to partially erect themselves. This is accomplished by the plant bending at one of its nodes. These nodes tend to enlarge and have the appearance of “elbows”. The rule of thumb, however, is that it is ‘three strikes and out’ when it comes to lodging. After both the first and second time that plants lodge the cells in nodes of lodged stems will stretch on the shaded side of the stem in an attempt to raise the stem upright. The crop can only do that approximately two times before it is unable to straighten itself up.

Lodging results from the combination of a number of factors, and is usually induced by strong winds. Lodging is most common in the later part of the crop’s growth, particularly during grain filling as more of the plant’s weight is shifted to the upper portion of the plant. The main factors that predispose a crop to lodging are:

  • High levels of nitrogen - N causes lush growth and heavier plant tissue. Excessive N can cause stems to be weak.
  • High seeding rates - With high plant densities there is less space for roots of individual plants, therefore, root systems are usually less extensive and less well anchored.
  • Wet soil conditions - Excessive soil moisture limits root development. Furthermore, roots in these types of soils often suffer from root rots. Wet soils do not anchor the roots of a plant as tightly as a dry soil.
  • Tall plant types or varieties with poor straw strength - Taller plant types are more prone to lodging as their center of gravity is higher than shorter plant types. Almost without exception, short varieties (dwarf types) are the most resistant to lodging. Within all plant height types, however, there is variability for lodging resistance and some varieties are just more prone to lodging than others. Although modern breeding programs screen their materials for lodging resistance, that does not mean that they all will have the same level of lodging resistance, nor does it mean you can manage them poorly and expect them to remain standing.

Yield losses resulting from lodging vary considerably. Some data suggests that losses up to 40% can occur if lodging occurs during the 10 days following heading. Yield losses will be much less if the grains are nearly filled. However, kernel damage and sprouting can occur in lodged fields that become wet. There may also be losses in labor as combining takes longer.

Some suggestions on how to reduce the risk of lodging:

  • Avoid excessively high seeding rates (higher populations do not necessarily mean, higher yield).
  • Grow a more lodging resistant variety. There a many well adapted varieties that have good lodging resistance.
  • Use crop rotations and other integrated pest management practices to reduce the incidence of root rots.
  • Use a plant growth regulator (PGR). PGRs have the potential for shorten plant height, which indirectly can reduce the risk of lodging. The timing of growth regulators can be critical in their effectiveness.

Corn-

Several years ago, I wrote an article for the Crop and Pest Report on root lodging in corn which I have modified and included here. Root lodging is not to be confused with green snap that I wrote about in a previous report. From my experience, green snap is more common than root lodging in North Dakota. Nevertheless, since I mentioned lodging in small grains, I thought I would include information on lodging in corn too. Root lodging occurs when roots are not able to anchor the plant against the force of the wind. Plant growth stage, rooting depth, root feeding by rootworms, wind velocity, soil moisture content at the time of heavy winds, and corn hybrid are factors that influence root lodging. Root lodging is most common during the mid-vegetative stage of development before brace roots have formed. Brace roots provide a valuable function in anchoring and supporting the plant and do not fully develop until after silking. Moist soil at the time of high winds increases the likelihood of root lodging as roots on the windward side of the plant are more easily pull from moist soil than those in dry or compacted soil. Rootworm feeding can dramatically reduce root mass and increase the potential for lodging (Figure 2). If you experience root lodging and are growing corn after corn, there is a good chance that lodging is related to rootworm injury. Rootworm populations have developed resistance to some of the rootworm traits, so even if you are using a traited hybrid, I would check the roots of lodged plants for rootworm feeding. Rootworm populations with resistance to one or more of the Bt rootworm traits have been identified in North Dakota.

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Like in small grains, corn plants that lodge before grain-filling have the capacity to erect the upper part of the plant by goose-necking at one or more of the lower nodes. Yield loss from lodging depends on plant stage with greater losses occurring in plants at a later growth stage. Losses of up to 31% were found in plants that were completely lodged when approaching tasseling or later (Carter and Hudelson, http://corn.agronomy.wisc.edu/Pubs/PC_JournalArticles/001-04-0295.pdf).

 

Joel Ransom

Extension Agronomist, Cereal Crops

This site is supported in part by the Crop Protection and Pest Management Program [grant no. 2017-70006-27144/accession 1013592] from the USDA National Institute of Food and Agriculture. Any opinions, findings, conclusions, or recommendations expressed are those of the website author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

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