More About Lodging
In the blog I posted on Dec. 3, 2016, I may have given the impression that lodging in soybean is not an important issue. That was not my intent, since lodging can be a serious production problem when it does occur. But with today’s varieties, it just doesn’t occur very often. The below narrative will provide more in-depth information about lodging, including its causes and when it can be a yield-reducing occurrence.
Most lodging scores that are recorded/published by breeders/researchers/specialists are based on the following scale.
1 = almost all plants erect.
2 = either all plants leaning slightly, or a few plants down.
3 = either all plants leaning moderately (<45° angle), or 25-50% of plants down.
4= either all plants leaning considerably (>45° angle), or 50-80% of plants down.
5 = all plants down.
Simulated lodging studies (Woods and Swearingin, Agron. J., 1977) have shown the following.
• Yield reduction declined in a linear fashion from R1 to R3 to R5 when lodging occurred at those stages. Lodging that occured at about the R5 stage (beginning seed) had the greatest negative effect on yield. Lodging at R6 had negligible effect on seed yield.
• Yield reductions due to lodging resulted primarily from a reduction in central stem yield. This is because apical dominance was lost when lodging occurred in the early reproductive growth stages. This loss of apical dominance resulted in longer and vertical lateral branches, and increased yield from branches. However, seed from lateral branches were smaller than those from the main stem.
• The major effect of simulated lodging on soybean was a reduction in the number of pods on the main stem.
The following are important points for assessing lodging occurrence or effect.
• Plants of varieties growing in later plantings on a silt loam soil likely will reach a height that will be conducive to lodging, and this should be considered when planting during this timeframe on loam soils. Click here for an example of this occurrence.
• Fertile soils that have adequate available water during soybean vegetative development will promote height that may be conducive to lodging.
• It is generally accepted that yield will not be adversely affected if lodging scores are less than 3 using the above scale.
• Plant height should not be used as in indicator of lodging potential. A good rule of thumb is that plants that are 36 in. or less in height likely will not lodge barring a weather catastrophe such as a hurricane. Conversely, plants of a variety that routinely exceed 40 in. in height will be prone to lodging in a moderate to high-yield environment.
• Environments such as May plantings that are grown on a silt loam soil and irrigated will generally promote taller plants which will be susceptible to lodging.
• Soybean varieties differ in their susceptibility to lodging. Therefore, use harvest standability scores when selecting soybean varieties for a particular soil environment or planting date. Most companies use a 1 to 9 scale, where 1 is excellent. However, check each company’s scale to ensure the range. Click here for company websites that can be accessed for these scores.
• A too-high plant population will result in taller plants with smaller stem diameters, and this may contribute to lodging.
• It is generally accepted that lodging will be a more likely problem in high-yielding soybeans. This, of course, will be related to the greater weight of a heavy pod/seed load on individual plants. According to David Holshouser, “...20 bushel soybean do not usually lodge”.
• Lodging from R6 (full seed) to maturity will have less impact on seed yield, but conversely can have negative effects on harvestability, which in turn can reduce harvested yield. This will likely require an adjustment in combine operation; e.g., ground speed, reel speed and location of reel in relation to cutter bar, harvest direction.
• The type of lodging is important. For example, soybean plants that are leaning because of a heavy pod/seed load may be considered as moderately lodged, but they will not have a reduced yield because of this type of lodging. Conversely, soybean plants that have a lodging rating based on a significant number of plants being “down”–the lower portion of the main stem is on the ground and has no pods at the lower nodes–will likely suffer a yield reduction because of the loss of apical dominance explained above.
So recognize that lodging can occur in certain environments or following certain weather conditions, and that lodging can cause yield loss. The best defense against its occurrence is to select varieties that are noted for having a moderate height and a good standability rating. Also ensure that the selected seeding rate 1) is necessary or recommended for yield optimization, and 2) will produce plants with a stalk size that will not normally lodge in the growing environment.