Edge of Field Syndrome in Corn: Reality or Myth?
Over the past five years or so, we have been hearing stories about fields of corn that show serious yield losses on the edge of the field, specifically on the South and West sides of corn fields, with yields as much as 50 bpa off the rest of the field. I have personally seen yield maps that suggest that this is a reality but explanations have been speculative at best.
Researchers at Iowa State and other universities have alluded to several scenarios that may help explain part of the yield deficiency but several cumulative environmental factors are the most likely culprit. Below are several potential explanations for this relatively new phenomena.
Herbicide drift. In the current ag climate, herbicide drift seems to get the blame for every visible issue we hear about in the country, especially as it pertains to dicamba. We recognize that poor timing of herbicide applications in corn can cause major yield losses. For instance, when Roundup is applied to corn at silking, this can cause roughly 25% of the kernels to abort. This phenomena has also been observed when aerial applications of fungicides with non-ionic surfactants also killed kernels. Could other herbicides be causing stress that lowers yield as well?
Differences in transpiration on the field edge. During the growing season, the middle of corn fields tend to be cooler due to better shading of the ground and higher plant density. As these corn plants respire water, it provides a cooling effect within the field. The edges of the field, however, are less dense and more prone to air movement through the canopy, which diminishes this cooling compared to the middle of the field. We see the same effect in the fall, as corn on the edge of the field is drier at harvest than the middle. Could dry wind blowing at the edges of fields be limiting yield due to more moisture stress as plants try to cool themselves?
Poor fertilizer applications. I have unfortunately witnessed several instances where custom applicators do not get fertilizer spread completely to the edge of the field. This may be due to wind at time of application or just poor management by the operator. A single year of poor fertilizer application would not necessarily show diminished yields in that cropping year. Estimates show that only 36-45% of our fertilizer applied is utilized by the crop in that year but one can envision how several years of poor fertilizer applications would have a negative effect at the edges of corn fields.
West edges historically yield worse. In fields planted in strips of alternating corn and beans throughout a field, growers have seen overall better corn yields than a solid field of corn. Data from the Northeast Iowa research farm have shown when individual rows are measured in these corn strips, the yield of the Eastern most row is substantially higher than the West row in a North/South planting orientation. Over 10 years of research, the bushel difference is a little more than 26 bpa! In these strips, the outside rows generally yield more than the inner rows, to the tune of roughly 90-100 bushel more, with exceptions occurring under severe stress as we saw in 2012 when outside rows have yielded less. Could the West edge of a field just naturally yield less?
In summary, if you are experiencing what you feel are edge of field yield losses, I would consider the potential issues above and suggest a few basic steps to eliminate each as a suspect. First, take a soil sample from the edge of the field where losses are occurring and compare those results to the middle of the field. Secondly, keep track of accumulated heat units as a guide for the growing year; extremely hot and dry conditions will lower yields but, under extreme heat and dry weather, the edge of the field may be hurt worse. This has been the case in Iowa the last 2 years. Finally, be very careful not to spray adjacent fields when your corn is tasseling to avoid stress at that pollination.
Frost and Cold Temperature Damage to Small Soybeans
Frost and Cold Temperature Damage to Small Soybeans
- Soybeans respond differently to frost compared to corn because the growing point is exposed to weather as soon as the cotyledons emerge.
- Understanding the effects of weather conditions on soybean at different growth stages can help determine the best management options.
Soybeans vs. Corn
Soybeans are more susceptible than corn to frost and cold temperatures. The growing point for corn remains below ground until corn reaches about V5 (5 visible leaf collars) growth stage. Comparatively, the growing point for soybean is above ground and exposed to the elements as soon as the cotyledons emerge.
If the main growing point (also called the apical meristem) is damaged, soybeans have a greater ability to recover than corn. Soybean plants can produce new growth auxiliary buds found at each node. When this regrowth occurs from the node where the cotyledons or unifoliate leaves were attached, it has been referred to as psi syndrome due to the shape.
Will the Soybean Plant Make It?
Frost damage to soybean plants can occur when temperatures range between 28 to 32 °F. Temperatures of 29 to 30 °F may be tolerated for short periods of time when soybeans are in the VE (emergence) to VC (unrolled unifoliate leaves) growth stages. Several days of cool temperatures can harden a plant, and when this occurs, temperatures of 28 °F may be tolerated. Complete death (buds, stems, and leaves) is not expected until temperatures remain at 28 °F for an extended period of time for sensitive plants. Soybeans in the VC stage are slightly more frost tolerant compared to soybeans in the V1(first-trifoliate) and V2 (second- trifoliate) growth stages. Soybeans with emerged trifoliate leaves (V1 and V2 growth stages) become more susceptible to temperatures below 32 °F for any extended time.
Patience is needed to determine if an individual soybean plant is likely to survive a frost. It helps to wait a few days before evaluating the potential for new growth at the auxiliary buds. In Figure 1, the plant on the left has been injured by frost for 24 hours and may have tissue death below the cotyledonary node. The plant on the right was injured by frost, but only down to the area above the cotyledonary node, allowing for regrowth from the auxiliary buds at that node. The growth from those auxiliary buds will be similar to that of the original plant had it not been damaged by frost. The odds of the injured plant on the right producing a respectable yield potential are very good.
Figure 1. Examples of frost damage to soybeans. Plants with severe frost damage that begins below the cotyledonary bud (left) may have tissue death. If regrowth at the cotyledonary node is seen (right), plants may contribute to yield.
Will the Soybean Plant Make It?
Replanting a field of frost-damaged soybeans demands more consideration since soybeans are more susceptible than corn to frost and cold temperatures. However, soybeans can tolerate stand reductions fairly well. Often, if a soybean stand is evenly distributed, replanting is not recommended unless populations are less than 100,000 plants per acre. As the season progresses, vigilant scouting should continue for seedling blights and environmental damage in soybean fields, especially those damaged by frost.
There are many resources available addressing soybean early growth and survival. Additional information on evaluating soybean early growth and survival can be found in the video blog developed by Extension Specialist Shawn Conley at http://ipcm.wisc.edu/blog/2014/05/new-video- soybean-emergence-and-germination-common-issues/.
Sources: Berglund, D.R. 2004. Spring frost damage to crops could be a problem. News. North Dakota State University. www.ext.nodak.edu. 120601023004
For additional agronomic information, please contact your local seed representative. Developed in partnership with Technology Development & Agronomy by Monsanto.
Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible. ©2017 Monsanto Company.120601023004. 051215SEK
2021: Ear Slippage a Concern – No Ifs, Ands or “Butts”
July is the pivotal month for corn growing, as growers and seed specialists like myself spend hours watching the highs and lows of each day, hoping to keep the highs below the 86 degree threshold while getting lows below 70 at night to give those corn plants a break. In cases of readily available moisture, these concerns are often not a major issue, but in much of the corn belt in 2021, drought stress has given much cause for concern for our fall harvest.
What are some of these concerns? First, in a lot of dry areas, the amount of corn rootworm beetle pressure is immense. I have been actively trapping beetles since the middle of July and some of the fields are showing an average of 43 beetles caught per plant per day! That is roughly 20 times the economic threshold. These numbers are downright scary thinking about the number eggs that these adults are laying and will be resulting in root-feeding larvae next year. Another threat potentially related to this drought stress and excessive rootworm pressure has me equally concerned for this year’s crop; poor kernel development at the butt of the ears.
Many of you who have been in the seed business for some time have encountered “ear slippage” in the fall. The bulk of the time, growers immediately want to blame the hybrid for their ears lying on the ground, but that is just not the case. One contributing factor to this is drought stress. The shank and ear are anatomically similar to the stalk above the ear attachment. Therefore, it is no surprise that if that portion the stalk is fragile from drought stress, so will be the shank. This year, another stress related cause of possible ear slippage is simply poor pollination of the butt of the ear. Note the arrowed areas of the picture below: overall the ears look filled out fairly well, but the kernel spacing around the butt is irregular. This causes those kernels to grow quite large and wildly out of place. Ultimately they push the ear away from the shank attachment. The result is ear slippage.
In addition to severe heat and extended drought at this stage of ear development, other factors can influence pollination. These include improper applications of some herbicides, insect feeding on early emerged silks that pollinate these first ovules, as well as poor fertility. Heat stress is usually the major culprit alone, or in conjunction with these other influences.
So what can be done if this is a potential problem? I would strongly encourage growers to spend some time this fall gauging whether or not this could be an issue as well as looking at general stalk quality and then prioritizing those fields for earlier harvest. There is really no solution other than harvesting while the ears are still intact. So check out your fields and put together a harvest plan, or you might feel the pain of ear slippage.