C.O.R.N. Newsletter: 2022-19
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Estimated and Soil Test Methods to Determine Supplemental N need after Flooding
Determining the amount of supplemental nitrogen, if any, that is needed after saturated soil conditions is a difficult question to answer. Soil conditions such as texture, temperature, and length of saturation plus nitrogen application factors timing, placement, source, inhibitors used along with the growth stage of corn which impacts the amount of N already taken up, affect the decision to apply additional N.
In Ohio, we have long used a tool adapted from the University of Minnesota that walks through five key questions. Points are assigned based on the answers to the questions posed and lead you to a recommendation. The tool is found in Bulletin 827 Corn, Soybean, Wheat, and Forages Field Guide (2019) on pages 81 and 82 or here. Given the current price of nitrogen and widely varying field conditions, an understanding of loss mechanisms and other estimates of loss or soil tests may help decide on 2022 management in fields where N has already been applied.
N Loss Mechanisms
The two primary loss mechanisms are leaching N below the soil root zone and denitrification with heavy rain and flooding. Leaching occurs with the nitrate form of N and is more typical on coarse-textured or sandy soils. Fine-textured soils with poor drainage where ponding occurs are where denitrification is most likely. Bacteria in the ground will use the oxygen from the nitrate molecule resulting in nitrogen gas. N gas formed is lost to the atmosphere. Bacteria will begin the denitrification process within two to three days of soil saturation (Lee et al., 2007).
Impact of N form applied
Nitrogen in the nitrate form is subject to leaching or denitrification losses. However, our fertilizer sources are a mix of nitrate and ammonium. The conversion of ammonium to nitrate requires time and the time needed depends upon soil temperatures and the use of a nitrification inhibitor. Using a nitrification inhibitor (e.g., nitrapyrin) can help delay the conversion of fertilizer nitrogen into the nitrate form. A nitrification inhibitor can potentially delay the conversion of ammonium to nitrate by 2 to 6 weeks, depending on environmental conditions (Omonode and Vyn, 2013; Havlin et al., 2014). However, this conversion delay is likely closer to 2 weeks at this point in the growing season due to warmer soil temperatures. A urease inhibitor can delay the conversion of urea to nitrate by 7 to 10 days.
Table 1. Approximate time until fertilizer nitrogen is in the nitrate form (Havlin et al., 1999)
Fertilizer Source
Approximate Time Until Ammonium
Approximate Time Until Nitrate
Ammonium sulfate, 10-34-0, MAP, DAP
0 weeks
1 to 2 weeks
Anhydrous ammonia
3 to 8 weeks
Urea
2 to 4 days
1.25 to 2.5 weeks
UAN
50% from urea in 2 to 4 days
25% is ammonium, 0 weeks50% in 1.25 to 2.5 weeks
25% in 1 to 2 weeks
25% is nitrate, 0 weeksEstimating Denitrification Losses
Soil temperature and how long soil is saturated also influence the amount of nitrate lost from denitrification. At soil temperatures between 55 to 65 degrees Fahrenheit, approximately 2 to 3% of soil nitrate is lost per day under saturated conditions. If the soil temperature exceeds 65 degrees Fahrenheit, around 4 to 5% of the soil nitrate is lost daily. Also, remember it takes approximately 1 to 2 days for saturated soil to reach anaerobic conditions.
Let’s think through an example where we made a side-dress application of 28% UAN at 150 lbs N/acre three weeks ago. Table 1 suggests that 100% of the UAN is now in nitrate form. If saturated soil conditions exist for 6 days with soil temperatures greater than 65 degrees, we expected a 20% loss [5% per day X 4 days (subtracted 2 days for the lag time until a saturated soil reaches anaerobic conditions)] of the 150 lbs N/acre was denitrified or lost (approximately 30 lbs N/acre). These calculations are strictly estimates and may not reflect actual N losses since so many factors interact in nitrate conversion and loss from the soil. An additional consideration is that corn submerged or ponded for 3 to 4 days may experience significant root damage, limiting supplemental nitrogen application benefits.
Estimating Leaching Losses
Determining the amount of N loss from leaching, like denitrification, also depends on the amount of nitrogen fertilizer applied in the nitrate form (Laboski, 2016) (Table 1).
Using an example of 150 lbs of N/acre of UAN containing a nitrification inhibitor applied 1 week ago in a side-dress application, only 25% of the UAN is likely in the nitrate form. Therefore, approximately 37.5 lbs N/acre has the potential to be leached with heavy rainfall. Keep in mind the crop has also taken up some nitrogen since application, so the potential N leaching loss is less than 37.5 lbs N/acre. Furthermore, nitrogen leaching is also dependent on soil drainage patterns and the total amount of water required for soil to reach field capacity (White, 2018). More significant nitrogen leaching loss is likely to occur on coarse-textured, sandier soil types than on fine-textured, loam, and clay soil types. Established rooting depth is also necessary to estimate potential nitrogen loss from leaching. Just because nitrogen has moved downward in the soil profile doesn’t mean the nitrogen has moved out of the root zone. This is especially true in seasons where dry conditions occur early and rooting depth increases.
With delayed planting and side-dressing in 2022, considering the timing of nitrogen applications compared to when flooded conditions existed in your fields is important to answer the question of if any supplemental N is needed?
Can a Pre-Sidedress Nitrogen test provide a better answer?
Taking the time to soil test, which gives a number to develop a recommendation, is an option for quantifying soil available N. For many years, the Pre-sidedress Nitrogen Test (PSNT) has been a valuable tool in making nitrogen recommendations in manured fields. Camberato and Nielsen, 2017 shared their thoughts on using a PSNT test to assess soil N availability from previous fertilizer applications.
The PSNT sampling method is to take 12-inch deep cores from representative areas of the field. Where fertilizer N was broadcast-applied rather than banded, collect 20 to 30 random soil cores per sample. If fertilizer N was banded rather than broadcast-applied, collect 15 to 20 groups of 5 soil cores each that proportionally represent areas with and without banded fertilizer. Take one core in the center of the band, then two cores on both sides of the center at a quarter and half of the band spacing. The lab results showing either a nitrate (ppm) or nitrate plus ammonium (ppm) can be compared to expected N levels shown in Table 2. The recommendation is If the corn is healthy and the growing season is expected to be typical from here on out, they suggest applying no more than 10 pounds of N for every 2 ppm reduction in soil sample N below the expected levels listed in Table 2.
Recognize that as a healthy crop moves through the rapid growth phase before pollination, soil N levels will naturally decrease in response to rapid N uptake by the plants. However, by the time a healthy crop reaches the V9 leaf stage (about 30 inches tall), only 19 lbs/ac N (equivalent to 5 ppm soil NO3-N in a 1-foot deep sample) have typically been taken up by the plants (Mengel, 1995). But, by the time a healthy crop reaches shoulder-high (~V15 or 60 inches tall), approximately 116 lbs/ac N (equivalent to 29 ppm soil NO3-N in a 1-foot deep sample) have been taken up by the plants. With later corn, the amount of N in the plant should be considered when evaluating soil N.
References:
Lee, C., J. Herbek, G. Schwab, and L. Murdock. 2007. Evaluating Flood Damage in Corn. AGR-193. University of Kentucky Cooperative Extension Service. http://www2.ca.uky.edu/agcomm/pubs/agr/agr193/agr193.pdf
Omondoe, R.A., and T.J. Vyn. 2013. Nitrification Kinetics and Nitrous Oxide Emissions when Nitrapyrin is Coapplied with Urea-Ammonium Nitrate. Agron. J. 105:1475-1486.
Havlin, J.L., J.D. Beaton, S.L. Tisdale, and W.L. Nelson. 1999. Soil Fertility and Fertilizers. An Introduction to Nutrient Management. 6th ed. Prentice Hall. Upper Saddle River, NJ.
Havlin, J.L., S.L. Tisdale, W.L. Nelson, and J.D. Beaton. 2014. Soil Fertility and Fertilizers. An Introduction to Nutrient Management. 8th ed. Prentice Hall. Upper Saddle River, NJ.
Quinn, D. 2021. Should Supplemental Nitrogen Be Applied To Corn Following Heavy Rainfall?. Pest and Crop Newsletter. Purdue University. https://extension.entm.purdue.edu/newsletters/pestandcrop/article/should-supplemental-nitrogen-be-applied-to-corn-following-heavy-rainfall/
Camberato, J and R. Nielsen. 2017. Soil Sampling to Assess Current Soil N Availability. Purdue University. https://www.agry.purdue.edu/ext/corn/news/timeless/AssessAvailableN.html
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Managing Corn and Nitrogen with Water Excess Conditions
Excess water challenges plant growth and fitness in farming systems. Depending on the geography, dramatic fluctuations and extremes in weather patterns have been experienced in Ohio, the US, and other parts of the world (e.g., droughts, floods). Research has shown that such events have increased in frequency and intensity over the past 50 years, making farming more challenging.
Not new to Ohio, wet conditions have been reportedly repeated in the last several weeks of the crop season, from April, May, and the first half of June of 2022. As a result, the crop has faced unfavorable conditions (Figure 1), and farmers have started to think about adjusting decisions for the rest of the season to reduce the impact of the damage.
Figure 1. Corn field under waterlogged and flooded conditions, Franklin County-Ohio, June 8, 2022.
The reports have ranged from waterlogging (i.e., the root system is under anaerobic conditions) to flooding (i.e., roots and some aboveground vegetation underwater) conditions (Figure 2). An excess of water has negative effects that can range from delaying planting, reduced seed/plant vigor, changes to normal growth/development, nutrient losses, water quality concerns, soil erosion, reduced nutrient uptake, and increased susceptibility to pests and disease pressures. Any of these conditions can have a detrimental impact on early crop establishment, continued growth, and development, and ultimately, it can reduce yields.
Figure 2. Plants encounter different scenarios due to excess water ranging from waterlogging to complete submergence. Source: Striker, 2012.
Nitrogen (N) is the primary nutrient of concern under waterlogged or flooded conditions. Nitrogen, particularly the nitrate form (NO3-), is a very mobile nutrient in the system (e.g., soils, plants, water, air), and can be lost due to leaching and denitrification. Therefore, nitrogen fertilizer applications in corn are often split into different timings (e.g., pre-planting, at planting, after planting) to gain N use efficiencies. Additionally, split applications can avoid losing the season’s N budget due to excess rain events.
Ohio base nitrogen rate recommendation comes from the Corn Nitrogen Rate Calculator (CRNC) found at http://cnrc.agron.iastate.edu/. The suggested nitrogen rate assumes best management practices for timing and placement of N. This tool does not provide recommendations for splits, percentages, sources, or forms to apply.
For applications yet to happen, here is a list of adjustments to consider:
Adjusting nitrogen fertilizer application timing: this is probably one of the most practical options. In general, corn requires approximately 30 lbs N before the V6 stage, and the remainder of the N uptake occurs after that growth stage. Consider lower pre-plant rates and plan to apply the rest of the needed N later in the season (possibly post-flood) to help minimize losses. Current research is underway to develop recommendations for combinations of pre-plant and side-dress rates. We will share our findings as they unfold.
Adjusting nitrogen fertilizer sources: some examples are enhanced efficiency fertilizers (EEFs) and organic fertilizers. Using EEFs may prevent and help minimize N losses such as leaching, denitrification, and volatilization. Although organic fertilizers are an option, the mineralization of organic sources (e.g., manure) may be affected by excess water. Additionally, some research suggests a connection between soil potassium (K) levels and N uptake, so ensuring soils are not limiting for K is important to optimize N uptake. We are looking into how N sources impact grain yield in the face of flooding, with results to come.
Adjusting nitrogen fertilizer placement/method: using more efficient placements, for example, 2 x 2. Delaying fertilizer applications becomes needed if field conditions do not allow equipment traffic across the field. The starter N can meet early crop needs until conditions improve. There still may be an ability for later-season N application (mid vegetative) with high clearance equipment if the traditional application windows for side-dressing (V4-V8) are too wet.
Additionally, besides adjusting nitrogen management, a list of other factors to consider include:
Crop insurance: the availability of crop insurance has been and continues to be a good risk management tool. The crop insurance payouts to farmers in the US for flooding damage averaged $24 billion between 2001 and 2011. With increases in the frequency and intensity of these events, economic losses are expected to be larger in current times.
Better hybrids: breeding programs have allocated some efforts to create materials with adaptive traits and acclimation responses to waterlogging and submergence of aboveground tissues. At the plant level, ethylene regulation seems to drive one of the adaptive responses. With current records, it is relevant to consider genetic materials when ordering seeds for the following crop season (i.e., flood-tolerant hybrids).
Use of cover crops: cover crops bring many services to the system. Those services relevant for flooding conditions include nutrient retentions, better soil structure, nutrient cycling, increased organic matter, reduced soil crusting issues, and increased biological activity. Note that biological activity is one of the fundamental processes for nutrient cycling (i.e., nitrogen) and making that into plant-available forms. However, cover crops may also cause challenges with soil dry-down, harboring negative pests, or causing additional logistical constraints (e.g., correctly timing termination). Research studies are underway in Ohio to answer some of these questions.
Use of drainage: drainage systems can be used when excess water is a concern. Drainage systems help to release the excess water present in a field. Different options exist; some are subsurface tile drainage and raised bed cultivation. These options are influenced by equipment availability, land topography, costs, and labor.
Adjust planting dates and replanting: planting later under better conditions can turn out better than planting early when conditions are not the best (e.g., wet soils) as an “avoidance” mechanism. Planting can be delayed if corn is used for silage. Depending on when flooding occurs, replanting can also be an option. However, later plantings would be compromised and may produce low yields due to the shortened growing season. If replanting, it is important to consider adjustments to shorter maturities to increase the chances of success. Recent work from Ohio suggested that good yields can be achieved with hybrids ranging in relative maturities of 95-104, access these results here. One of the main risks of replanting (i.e., late planting) is that the crop can get frost killed in the fall before achieving physiological maturity. Information on Delayed Corn Planting is available here.
Pest & disease monitoring & applications: seedling issues can be increased due to flooded and waterlogged soil conditions. Some factors that can exacerbate this concern include soil compaction, stunted plant growth, low seed quality, low seed/plant vigor, and crusted soils. In general, and depending on the timing and duration, any pest or disease presence can reduce plant growth and yields. To alleviate some of this, periodic monitoring and spray applications may become necessary.
Summary
A comprehensive understanding of corn’s morphological, developmental, and physiological responses to waterlogging and flooding is critical for preparing and adjusting to such conditions to minimize yield and economic losses. Some of this work is currently under research in Ohio conditions; updates and results will be shared as we learn more.
References:
Bailey-Serres, J., Lee, S. C., & Brinton, E. (2012). Waterproofing crops: effective flooding survival strategies. Plant Physiology, 160(4), 1698–1709. https://doi.org/10.1104/pp.112.208173
Kaur, G., Motavalli, P. P., Nelson, K. A., Singh, G., & Bararpour, T. (2020). Soil Waterlogging and Nitrogen Fertilizer Source Effects on Soil Inorganic Nitrogen. Journal of the Mississippi Academy of Sciences, 65(3), 300+. https://link.gale.com/apps/doc/A638130728/AONE?u=anon~d3f7e229&sid=googleScholar&xid=d6e38e7d
Souza Krupek, F., Redfearn, D., Eskridge, K. M., & Basche, A. (2022). Ecological intensification with soil health practices demonstrates positive impacts on multiple soil properties: A large-scale farmer-led experiment. Geoderma, Volume 409: 115594. https://doi.org/10.1016/j.geoderma.2021.115594
Striker, G. G. (2012). Flooding Stress on Plants: Anatomical, Morphological and Physiological Responses. In: Mworia, J. K., editor. Botany. https://www.intechopen.com/chapters/32711
Voesenek, L.A.C.J., & Bailey-Serres, J. (2015). Flood adaptive traits and processes: an overview. New Phytol, 206: 57-73. https://doi.org/10.1111/nph.13209
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100th Episode- Agronomy and Farm Management Podcast
The AFM podcast released its 100th episode this morning. Since 2018, we have covered a myriad of topics to address concerns in the field and the farm office. Each listener has helped take us to the top as one of the most listened to podcasts published by The Ohio State University. We thank you immensely for tuning into each new episode. In our 100th episode, we take a look back at all that has happened since 2018: the big prevent plant issue in 2019, the pandemic in 2020, and the impacts that continue to hit us 2 years later. A few of our favorite guests join us for this episode to reflect on the last 4 years and predict where we are going.
This summer we will cover the latest in drone spraying, how to get wheat off to a good start, provide some ag law updates, along with several other topics.
Subscribe on Apple or Stitcher or listen online at podcast.osu.edu/agronomy. We welcome feedback and topic suggestions at: go.osu.edu/afmsurvey.
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Summer Crop Insects – What to Watch For
Almost every field season has its particular insect problems and surprising‘ gotcha’ moments (we’re looking at you, fall armyworm). But there is a seasonality to our common insect pests in agriculture, and this article outlines a few of the things to look out for in the remaining months of summer. We will continue to monitor Ohio insect problems and provide more in-depth updates as needed.
July
- Soybean defoliators of various types (caterpillars, Japanese beetles, etc.) often make their first appearances in July. Thresholds for defoliation in soybean have recently been revised to take into account modern crop values and input costs. Soybeans can tolerate a surprising amount of defoliation and still compensate for a good yield, so don’t pull the trigger too soon. When deciding when to spray, make your decision based on the average condition across the whole field. Many soybean defoliators are concentrated on the edge and spraying the whole field will not provide an economic return.
- Potato leafhoppers are a potential threat to alfalfa from July through September. See our article from last week on scouting specifics.
- July is Western bean cutworm month in corn, but this pest varies widely from year to year. Check our weekly monitoring network for WBC and other moths/caterpillar pests, reported in the CORN newsletter each week. The flight usually begins in mid-June, but peak flight usually occurs in Mid-July.
- Stink bugs in soybean make their first appearances as pods begin to form. From R3 onward, keep an eye on them. This is another edge pest, and swelling populations can benefit from an edge application when needed.
August- Keep watching those potato leafhoppers in alfalfa.
- Defoliators and stink bugs in soybean tend to ramp up in August so keep these on your radar screen.
- Spider mites can strike many different crops during periods of sustained hot a dry weather, which can happen at any time of year but happens most commonly in August. There are several newer miticides on the market which are very effective when used timely.
- Remember soybean aphids? They are still a pest, but not as significant as before. If your field is infested, now is the time when they can cause damage.
September
- If you have late-planted soybeans that are still green in September when other beans are maturing, they will be a magnet for both stink bugs and bean leaf beetles. Bean leaf beetles feeding on foliage are seldom a problem earlier in the season. But pod feeding on late-season beans holds more damage potential, through direct damage to the seed and also through the introduction of disease.
- When planting winter wheat, be mindful of the fly-free date for your county. Planting after this date can help minimize damage from Hessian fly and also feeding by aphids which can transmit disease, especially barley yellow dwarf virus
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It’s Getting Hot in Here
The 2022 crop has already seen its fair share of stress. But with the forecast of a flash drought and much higher than normal June temperatures, we will be seeing some extra stress that we may normally anticipate for later in the growing season. Nevertheless, our crops are very resilient.
The original corn plant was a tropical grass that can tolerate temperatures up to 112°F for a short amount of time, but optimal daytime growth ranges from 77°F to 91°F, though 86°F is what is used for growing degree days because that is the average temperature where a corn plant will start to experience water stress. Corn growth starts a rapid decline when temperatures exceed 95 degrees.
Temperatures exceeding 86°F can be calculated as stress degree days, which is a way of tracking how much stress a type of plant has been subjected to. According to agronomists with Iowa State, in years when corn exceeds 140 stress degree days, achieving above-average yield is difficult.
However, according to agronomists at the University of Illinois afternoon temperatures in the mid-90s are not usually a problem for corn when there is enough soil water available. Temperatures above 100°F can begin to damage leaves. Though it is important to remember adequate water can increase the ability of the plant to handle heat stress. The combination of dry and hot is more damaging.
Leaf rolling is a common symptom of high-temperature stress. Yield diminishes by 1% for every 12 hours of leaf rolling during vegetative growth but increases to 1% every four (4) hours during silking. When water is deficient during a heat wave the loss of yield increases after four consecutive days of 93°F or above, not including the stress from leaf rolling. So, the impact of heat stress can be two-fold.
Soybeans have a similar range in temperature to corn for heat stress. Temperatures above 85°F for several consecutive days can cause heat stress. This heat can accelerate maturity because soybeans are photoperiod and temperature-controlled when it comes to flowering. During vegetative stages, these high temperatures can slow or stop photosynthesis because the plant is making an effort to conserve water. Thus, inhibiting new vegetative growth, which is vital for late-planted soybeans. Temperatures above 86°F can also reduce nodulation and therefore N-fixation in the soybean which could have an effect until the reproductive stages.
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Lep Monitoring Update CEW and ECB Updates
Corn Earworm
Corn earworm (CEW) traps were set the week of June 6th and first trap catches were recorded for the week of June 13th through 19th. Moth numbers in all counties are currently low; however, moths were present in six of the monitoring counties (Figure 1). Moths are most attracted to silking corn, where eggs are laid and the caterpillar damage developing corn. Corn earworm is more commonly associated as a pest of sweet corn, it is possible to find CEW in field corn. Monitoring for CEW will continue through August.
Corn Earworm moth map
June 13 – 19, 2022
Figure 1. Average corn earworm (CEW) moths captured from June 13th through June 19th. The large number indicates the average moth count for the week and the small number in parentheses is the total traps set up in the county.
European Corn Borer
European corn borer (ECB) numbers remained low over the past week with no reports of ECB-NY and only two counties (Fulton and Hardin) reporting ECB-IA (Figure 2).
European Corn Borer moth map
June 13 - 19, 2022
Figure 2. Average European corn borer (ECB) moths were captured from June 13th to June 19th. The first number indicates the average ECB-IA followed by a comma and then the average ECB-NY moth count for the week. The small number in parentheses is the total traps for each species set in each county.
Crop Observation and Recommendation Network
C.O.R.N. Newsletter is a summary of crop observations, related information, and appropriate recommendations for Ohio crop producers and industry. C.O.R.N. Newsletter is produced by the Ohio State University Extension Agronomy Team, state specialists at The Ohio State University and the Ohio Agricultural Research and Development Center (OARDC). C.O.R.N. Newsletter questions are directed to Extension and OARDC state specialists and associates at Ohio State.
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Disclaimer
The information presented here, along with any trade names used, is supplied with the understanding that no discrimination is intended and no endorsement is made by Ohio State University Extension is implied. Although every attempt is made to produce information that is complete, timely, and accurate, the pesticide user bears responsibility of consulting the pesticide label and adhering to those directions.
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