UT Extension- Fayette County

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Disease updates and fungicide considerations in corn and soybean
Author: Heather Marie Kelly, Extension Plant Pathologist

Armyworms Appearing
Author: Sebe Brown, IPM Extension Specialist

Over the past couple days, I’ve gotten a few reports of fall armyworms in pastures on the Mississippi/Alabama border with Tennessee. Tennessee will still have armyworms that migrate North and infest pastures, food plots and the occasional yard every year. However, the situation that happened in 2021 was a very unique event and will not occur yearly. That being said, reports of armyworms in 2024 are roughly two weeks earlier than what we typically see.

Fall armyworms don’t overwinter in Tennessee and populations migrate North from Texas and Florida every year. The difference in 2021 vs 2023-24 is the conditions that were occurring in April and May in South Texas. Texas experienced a warm and unseasonably wet spring that allowed for the proliferation of extremely large numbers of armyworms. Large numbers of moths plus ample food supply in pasture grasses, fallow grasses, yards and pretty much anywhere that had grass allowed this “army” to make its way North. Texas experienced outbreaks first followed by Louisiana, Arkansas, Mississippi then Tennessee with the moth flight culminating, in Canada, in November. I ask my colleagues, in Southern states, weekly if they are seeing any armyworms or anything resembling what happened in 2021 and the answer has consistently been no. My colleagues in Arkansas are getting calls about armyworms in rice and pastures but nothing even close to what was experienced in 2021.

If you do see armyworms it shouldn’t be automatically assumed that pyrethroids won’t be effective. We don’t fully understand why pyrethroids provided inconsistent control in 2021. Resistance is a possibility but overlapping generations causing mixing of various worm sizes resulting the appearance of poor control is another possibility. Also, since armyworms don’t overwinter in Tennessee and there is no evidence of reverse migration, the armyworms we experienced in 2021 won’t be the same ones we see in subsequent years. However, if pyrethroids do fail to control armyworms please contact your local county agent.

Going forward, pasture treatments should be considered when armyworm populations exceed 3 to 4 worms per square foot. If fields are ready or near ready for cutting, harvesting is suggested rather than applying an insecticide. Producers may watch for the presence of birds in a field as an indicator of armyworms. This method should not be the only one used to check for armyworms because this indication often is too late to avoid field injury. Early signs of infestations by small larvae cause plants to have a “window-paned” appearance. This is due to the larvae’s inability, at small sizes, to chew completely through the leaf blade leaving the upper epidermis intact. Large areas of window panning will give fields a frosted appearance. Ideally, scouting should be initiated in late July to early August without the presence of birds or frosted patches appearing so infestations can be caught early. When scouting during times when armyworms are not feeding (midday) be sure to dig through the thatch layer and check the base of plants. Detection of frass (insect excrement) is also a sign that armyworms may be present in a field.

The take home is scout early and often for armyworms in pastures, hayfields and turf areas. It may be prudent to initiate scouting earlier than we’re accustomed to catch any early infestations that may slip by.

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2024 County Standardized Trials-Wheat data
Author: Ryan Blair, County Variety Trial Coordinator
This year’s County Standardized Trials, Wheat Program tested 23 varieties of Soft Red Winter Wheat in 10 locations. Seven of those locations where used to compile our variety recommendations for the 2024 fall planting. Over all, yields across varieties and locations averaged just over 76 bu/ac, with an average of 10.4% moisture and 55.1 lb testweight.

Thank you to all the producer who put these trials out and the County Agents who organized and oversee these variety plots. Also, a special thanks to our cooperating companies who supply seed and genetics to test in our environment. Wheat yields have increased dramatically over the years, better genetics and breeding programs along with state and local testing are proving to add weight to the combine and increase profits for wheat growers in TN.

If you are interested in having a County Standardized Trial (Corn, Soy, Cotton, Wheat) on your farm, contact your local County Extension office for more details.

This Fall, contact your seed suppliers and request wheat seed from the list above with confidence from our unbias variety testing program.

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Tarnished Plant Bug Considerations in Blooming Cotton
Author: Sebe Brown, IPM Extension Specialist
TPB Adult
TPB Adult
Tarnished plant bug numbers seem to be all over the board in 2024. Some fields have one spray since square set and others have had upwards of five. Crop age and what’s neighboring your cotton play a large part of how intense plant bug pressure is over time. That being said, keeping an eye on square retention is the best gauge to determine how well your insecticides are performing. Most I’ve talked to have applied Diamond at least once since first bloom. Diamond shines when you catch early plant bug hatches often after large adult migrations during late squaring and we see a good ROI with Diamond around that 1st week of bloom timing.

Going into bloom, I don’t think neonics have a fit in any scenario. Every time we test a neonic sprayed after bloom its often one of, if not, the worst treatments in the test. Once you see a flower migrate to the Transform, Acephate, Bidrin treatments. Pyrethroids can be added in with OP’s to help increase control and acephate + pyrethroid can catch a few bollworms in the top of the canopy if you’re close to cut out (although our 3 gene cottons are doing a great job of controlling bollworms). Diamond should rotated around in the bloom mix also. Overlapping Diamond residual, usually spaced out every other shot, can help reinforce control of nymphs. I don’t like Diamond fb Diamond in succession. Diamond’s effects may take 7 to even 10 days to notice and sequential shots may not take full advantage of the residual it provides, but that’s situation dependent.

Thryvon bloom performance is on par with what we’re accustomed to seeing. Square retention is often better in Thryvon and plant bug numbers, especially nymphs, are lower. Insecticides seem to perform better in Thryvon for a couple of reasons. Less insects are typically easier to control, plant bug population growth is slower and we think the nymphs don’t settle in bracts/blooms like they do in non-Thryvon. Nymphs are constantly moving in Thryvon and the more they move, the higher likelihood they’ll encounter an insecticide. Final note, Thryvon has minimal, if any, activity on stink bugs and if you’ve gotten by without using a broad-spectrum insecticide mid to late bloom, I would add an OP or pyrethroid to clean up any building/lingering populations.

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Reminder-Beef meeting tonight. If you have not already, RSVP the Extension Office-901-465-5233.

✨ 🍏Ready to Jam into the Fair?🫐 ✨
Hey Fayette County friends! Do you have some amazing homemade jams, jellies, or preserves? We'd love to see them shine at the Wilson County State Fair! 🎉

Drop off your delicious creations at the Fayette County office by August 2nd, 2024 to enter the Tennessee State Fair Canning Competition! 🏆

For more details, visit: https://tiny.utk.edu/2024StateCanningCompetition .

Let’s show off Fayette County’s finest! ✨🍓 🍑✨

July is UV Safety Month! Protect your skin by wearing sunscreen, seeking shade, and wearing protective clothing. Stay safe in the sun!

Grass W**d Management Escapes
Author: Larry Steckel, Extension W**d Specialist

Infestation of goosegrass in cotton 2024
Serious infestations of goosegrass, junglerice and barnyardgrass have proven to be way too persistent in many cotton and soybean fields. Many are getting frustrated with the lack of control seen with tankmixes that contain glyphosate and/or clethodim or quizalofop. Some have asked if maybe some of these grasses have developed resistance to glyphosate, clethodim and quizalofop.

Resistance is indeed part of the reason for the lack of grass control with glyphosate. I do not believe dim or fop resistance is in the mix at this time. Rather I think there are a couple of other issues that are involved.

First, the robust rates of dicamba routinely applied to control Palmer amaranth greatly inhibits the control clethodim and quizalofop can provide on those grasses. This is definitely the case when dicamba is tankmixed with those herbicides. Moreover, the dicamba antagonism affect can linger a couple weeks. As such, clethodim or quizalofop applied even 10 days after dicamba can result in less goosegrass and junglerice control.

The other issue is the frequent showers that have delayed herbicide applications in many cases. Also in a few cases some of these applications have not gotten sufficient time on the grass before a rain event washes the herbicide off the leaf.

As far as management going forward the best approach is to use a high rate of clethodim applied with a good COC, preferably applied about 10 days after any dicamba application.

Reminder-please put our next up-coming beef meeting on your calendar. RSVP the Extension Office-901-465-5233.

July is here, and so is National Picnic Month—let's spread out the blankets and enjoy the great outdoors!

Grass W**d Management Escapes
news.utcrops.com/2024/06/grass-w**d-management-escapes/
Larry Steckel, Extension W**d SpecialistJune 28, 2024

Infestation of goosegrass in cotton 2024
Serious infestations of goosegrass, junglerice and barnyardgrass have proven to be way too persistent in many cotton and soybean fields (Picture 1). Many are getting frustrated with the lack of control seen with tankmixes that contain glyphosate and/or clethodim or quizalofop. Some have asked if maybe some of these grasses have developed resistance to glyphosate, clethodim and quizalofop.

Resistance is indeed part of the reason for the lack of grass control with glyphosate. I do not believe dim or fop resistance is in the mix at this time. Rather I think there are a couple of other issues that are involved.

First, the robust rates of dicamba routinely applied to control Palmer amaranth greatly inhibits the control clethodim and quizalofop can provide on those grasses. This is definitely the case when dicamba is tankmixed with those herbicides. Moreover, the dicamba antagonism affect can linger a couple weeks. As such, clethodim or quizalofop applied even 10 days after dicamba can result in less goosegrass and junglerice control.

The other issues is the frequent showers that have delayed herbicide applications in many cases. Also in a few cases some of these applications have not gotten sufficient time on the grass before a rain event washes the herbicide off the leaf.

As far as management going forward the best approach is to use a high rate of clethodim applied with a good COC, preferably applied about 10 days after any dicamba application.

2024 UT Soybean Scout Schools

Author: Sebe Brown, IPM Extension Specialist
UT’s Soybean Scout Schools will be held in July (see details below). These field-side programs cover the basics of soybean growth, scouting, pest identification, and general management. Pesticide recertification and CCA CEU points will be available. Scout Schools are offered free of charge with sponsorship from the Tennessee Soybean Promotion Board. Registration is not required. Participants will receive a scouting notebook and a sweep net while supplies last.

West TN – Madison County, July 15th, 9:00 AM – 11:30 AM. This school will be at the West TN Research and Education Center, 605 Airways Blvd. Jackson TN, 38301. Signs will be up at the station to direct you to the field.

Today is National PTSD Awareness Day

Today is National Yoga Day

TAPA Annual Meeting- July 22-24th- book rooms now!
Author: Tyson R***r, Cotton & Small Grains Specialist No Comments



TAPA Meeting Registration : https://tapa.tennessee.edu/meetings/

The Lodge at Pickwick Landing
Below is the direct URL for attendees to book through. Group code is good through June 21! You are welcome to call directly at 731-689-3135 x 0 or the call center at 888-867-2757 use code 25213.

Pickwick Landing State Park — Tennessee State Parks (reseze.net)

Thank you,
Julie

Julie Reeves
Research Associate
University of TN
Dept. of Plant Sciences
WTREC, Jackson, TN
731-415-041

Meetings | Tennessee Agricultural Production Association (TAPA) Annual Meeting Name* First Last Title Representing Address* Street Address Address Line 2 City State / ProvinceAlabamaAlaskaAmerican SamoaArizonaArkansasCaliforniaColoradoConnecticutDelawareDistrict of ColumbiaFloridaGeorgiaGuamHawaiiIdahoIllinoisIndianaIowaKansasKentuckyLouisianaMaineMarylandMassac...

Tarnished Plant Bugs Migrating into Squaring Cotton
Author: Sebe Brown, IPM Extension Specialist

I’ve received a few calls on adult tarnished plant bug migration into squaring cotton. Silking corn, blooming soybeans and flowering pigw**d all contribute to large increases in plant bug numbers that make their way to ThryvOn and non-ThryvOn cotton. ThryvOn’s bt gene can help reduce the amount of injury plant bugs inflict to squaring cotton but adults, especially large numbers of adults, can knock squares off of ThryvOn just like non-ThryvOn. I’ve seen ThryvOn cotton go from 90 plus percent square retention to sub 50 percent in 5 days due a large, consistent migration of adult plant bugs. The biggest benefit we see from ThryvOn is the reduction of plant bug immatures in bloom. That being said, you will typically see increased square retention in ThryvOn vs non-ThryvOn throughout the fruiting period. Scout your cotton and don’t ignore migrating plant bugs in ThryvOn or non-ThryvOn. Also, many of the newer varieties begin squaring on the 5th or 6th node and we need to quickly transition from scouting for thrips to plant bugs.

Based on field reports, 2.0 oz/a of Centric is performing well on plant bug populations. Although the same class of chemistry, imidacloprid’s performance is fair at best and recolonization often happens quickly after an imidacloprid application. I try to not recommend consecutive applications of neonics due to efficacy falling off after the first shot. However, consecutive shots of neonics may be warranted for several reasons (cost, presence of mites, personal choice etc.) and on the second application I tend to increase rates of Centric to 2.5 oz/a especially if it was used previously. After the second application we’ve pretty much exhausted that chemistry. Other options are: acephate which carries a high risk of flaring mites and aphids especially in our current dry period, Vydate which is effective in killing plant bugs but has limited residual, roughly 36 hours, Bidrin isn’t labelled for plant bugs between first square and bloom, Transform, which is very effective, but is expensive and many want to save those shots for bloom unless aphids are present and Diamond. Diamond’s activity is best utilized in the 3rd week of squaring to first bloom window, several studies at MSU and UT have shown the best ROI of 6.0 fl oz/a Diamond during that time period.

Final note, I’ve received a few questions on squaring cotton having poor square retention but very few or no plant bugs are found scouting. Adult plant bugs, especially at this time of year, will move in and out of cotton quickly. The abundance of alternative hosts facilitates movement in and out of cotton without colonization. The take home is since most are scouting once a week, it is prudent to be more aggressive with applications and not risk square retention falling below 80% if you’re close. Monitoring square retention is one of, if not, the best way to determine if early-season treatments are working. Migrating adults can give the impression of an insecticide failure, but maintaining good square retention is a good indication that treatments are working.

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W**d Tour Next Thursday June 20
news.utcrops.com/2024/06/w**d-tour-thursday-june-20/
Larry Steckel, Extension W**d SpecialistJune 13, 2024
JACKSON, Tenn. – The University of Tennessee Institute of Agriculture will host the annual W**d Tour next Thursday, June 20 at the West Tennessee AgResearch and Education Center. The guided tour will feature 60 w**d management research tests in cotton, corn and soybean.

W**d Tour runs from 9 – 11:30 a.m., with registration opening at 8:30 a.m. A light breakfast will be served.

Larry Steckel, UT Extension w**d specialist, will lead the tour, along with Dr. Lauren Lazaro, Senior Agronomist with Blue River Technology.

“Most of the research featured in the 2024 W**d Tour involves management of glyphosate-resistant grass species and multiple herbicide-resistant Palmer amaranth,” says Steckel. “Management of these w**ds in Liberty, Axant, Xtend and Enlist w**d control systems will be highlighted.”

Steckel says the tour will also cover research-based strategies to manage the increasing problem with glyphosate-resistant grass species, as well as glyphosate/PPO/dicamba-resistant Palmer amaranth. A tractor-mounted See & SprayTM test system from John Deere that uses visual recognition and machine learning to selectively spray pesticides in crop fields rather than broadcasting herbicides over the entire area will be shown.

At the conclusion, tour leaders will be available for consultation, as well as discussion of issues and product performance.

The West Tennessee AgResearch and Education Center is located at 605 Airways Boulevard, Jackson, Tennessee. Upon arrival, follow signs to the w**d management research plots. For directions, or more information, call 731-425-4705.

Through its mission of research, teaching and extension, the University of Tennessee Institute of Agriculture touches lives and provides Real. Life. Solutions. ag.tennessee.edu

Late Burndown in Soybean
news.utcrops.com/2024/06/late-burndown-in-soybean/
Larry Steckel, Extension W**d SpecialistJune 13, 2024

Picture 1. 3 foot tall goosegrass, fall panicum and Palmer amaranth that need to be burndown before soybean planting
The question of the week is on how to burndown fields that are grown up messes before planting soybeans (Picture 1). The problem is when fields are heavily infested with 3’ tall goosegrass, Palmer amaranth, horsew**d and volunteer corn that is tasseling there are no good answers.

Paraquat, the usual “go to” for late spring burndown, will not control grasses with size or even pigw**d that has gotten so far out of hand. As such, the best approach is aggressive tillage. That unfortunately is not an option on our highly erodible fields.

In those cases, a tankmix of a high rate of Liberty plus clethodim is the best approach to try to control the grass w**ds and set the pigw**d back. Then, if possible, a couple days later apply paraquat. This approach would have the best chance of success with herbicides.

In fields where the soybeans may emerge before a follow-up paraquat application could take place then a dicamba application in XtendFlex soybean or Enlist application in Enlist soybean followed shortly by Liberty is the last best hope.

Late Burndown in Soybean - UT Crops News The question of the week is on how to burndown fields that are grown up messes before planting soybeans (Picture 1). The problem is when fields are heavily infested with 3’ tall goosegrass, Palmer amaranth, horsew**d and volunteer corn that is tasseling there are no good answers. Paraquat, the usu...

June is Men's Health Month! See below for 3 quick tips to keep you feeling your best!

Please put our next up-coming beef meeting on your calendar

Beef Producers pack UT Somerville Center

Beef cattle farmers packed UT Somerville Center on June 6, 2024 to hear Charles Hord, Executive Director of the Tennessee Cattleman’s Association. Charles spoke on a variety of topics including disease traceability, fake meat, black vultures, the Farm Bill and MRNA vaccines to name a few. UT Extension has been working with the Fayette County Livestock Association for some time. Based on needs assessments, topics and speakers are chosen. According to Jeff Via, Director of UT Extension-Fayette County, “Our group has grown and continues to grow. We moved to UT for more room and I hope more folks will continue to come and see the value we provide.

Nitrogen loss potential in wet corn fields
news.utcrops.com/2024/06/nitrogen-loss-potential-in-wet-corn-fields/
June 3, 2024
From late April and throughout the month of May, many parts of Middle and West TN have received persistent rainfall that is well above the average for this period. These rains have produced persistently wet soil conditions and have coincided with sidedress N fertilizer application where most or all of the recommended N is applied. With this much rain, there is potential for N loss.

Generally, surface-applied unincorporated urea-based fertilizers, are susceptible to N loss via ammonia volatilization, denitrification, surface runoff, and leaching. However, the potential for N loss through denitrification and leaching are of special concern with during periods of excess rainfall and saturated soils.

Leaching involves the movement of nitrate-N (NO3–) with water below the root zone. Nitrate is water soluble, loosely bound to the soil, and therefore susceptible to leaching once the soil is saturated. Soil nitrate that moves below 4 feet is unrecoverable by most crops. Leaching is a greater risk if excessive rainfall occurs shortly after N fertilizer application, when the concentration of nitrate in the soil is high. Soil properties such as texture, structure, bulk density and depth to restrictive layers play major roles in leaching potential. In fine-textured soils with slow percolation, N loss via leaching may be negligible; however, in coarse textured soils where water percolates freely, 20 percent of applied N can be lost by leaching. Since most of the soils throughout Middle and West TN are not coarse-textured, the loss of N via leaching may not be substantial.

In contrast, denitrification is the conversion of nitrate into nitrous oxide (N2O) or dinitrogen gas (N2) when the soil is ponded continuously for at least 2 days. The gases produced during denitrification escape into the atmosphere and reduce the amount of N available for plant uptake. The rate of denitrification is greater in soils containing residue, which serve as food sources for the microbes. Depending on soil properties and environmental conditions, N loss via denitrification may account for 5-25 percent of the total N applied.

In saturated conditions, the dominant N-loss pathway for our soils will be denitrification. So, how would you estimate the amount of N loss as a result of denitrification from your field? The estimate will depend on the nitrogen source applied, the soil temperature at application, the amount of applied N in the nitrate form, and how long the soils have been saturated. Research at the University of Nebraska (click here), provides information on the proportion of applied N that would be in the nitrate form over time. Application of urea ammonium nitrate would result in more nitrates being present when compared to urea if application was made a few weeks prior to flooding or saturated soil.

What should you do now? Corn that appears yellow in a temporarily flooded field does not indicate all of the N has been lost or that the crop is deficient. Most of the N may still be still present, especially for sidedress N applications. The narrative is quite different for fall or winter applications, where denitrification loss will be higher considering most of the N is in nitrate form. Producers who applied all their N in the fall, winter, or early spring should make plans to apply additional N if needed.

POST Control of Palmer Amaranth in Corn and Soybean
news.utcrops.com/2024/06/post-control-of-palmer-amaranth-in-corn-and-soybean/
Larry Steckel, Extension W**d SpecialistJune 4, 2024
Last fall there was a notable amount of Palmer amaranth in many corn fields in areas of the state where we had confirmed dicamba resistance. As a result, we have recently conducted some field screens on these pigw**d populations to herbicides used in corn and soybean.

In the first study we saw a lack of Palmer control from topramezone with rates as high as 3 ozs/A (Figure 1). On the topramezone label it states that Palmer amaranth can be controlled with rates of 0.75 to 1.0 oz/A if applied to w**ds that are less than 6” tall. Our applications were made to Palmer that was 4” tall. This is a very unwelcome result.

Another test examined dicamba, 2,4-D, glufosinate, 2,4-D + glufosinate, atrazine, topramezone and atrazine + topramezone. These herbicides were applied at their commonly used rates. The poor performance of dicamba and 2,4-D were expected from previous research in this area. The less than stellar control with glufosinate is not uncommon. The disappointing performance of atrazine and topramezone were new findings (Figure 2).

Figure 2

The tankmix of atrazine + tompramezone provided better control than either herbicide applied alone. Unfortunately, it was less than 70% control, which would be consistent with field observations last fall.

On the positive side, where Enlist crops are concerned as well as in corn, 2,4-D + glufosinate provided 80% Palmer amaranth control. Two applications of that tankmix applied about 10 days apart appeared to be the only labeled POST applications that can provide something close to acceptable control.

All these data would suggest the importance of applying effective PRE-applied herbicides and overlaying more residual herbicides POST.

W**d Tour Thursday June 20
news.utcrops.com/2024/06/w**d-tour-thursday-june-20/
Larry Steckel, Extension W**d SpecialistJune 5, 2024
JACKSON, Tenn. – The University of Tennessee Institute of Agriculture will host the annual W**d Tour on Thursday, June 20 at the West Tennessee AgResearch and Education Center. The guided tour will feature 60 w**d management research tests in cotton, corn and soybean.

W**d Tour runs from 9 – 11:30 a.m., with registration opening at 8:30 a.m. A light breakfast will be served.

Larry Steckel, UT Extension w**d specialist, will lead the tour, along with Dr. Lauren Lazaro, Senior Agronomist with Blue River Technology.

“Most of the research featured in the 2024 W**d Tour involves management of glyphosate-resistant grass species and multiple herbicide-resistant Palmer amaranth,” says Steckel. “Management of these w**ds in Liberty, Axant, Xtend and Enlist w**d control systems will be highlighted.”

Steckel says the tour will also cover research-based strategies to manage the increasing problem with glyphosate-resistant grass species, as well as glyphosate/PPO/dicamba-resistant Palmer amaranth. A tractor-mounted See & SprayTM test system from John Deere that uses visual recognition and machine learning to selectively spray pesticides in crop fields rather than broadcasting herbicides over the entire area will be demonstrated.

At the conclusion, tour leaders will be available for consultation, as well as discussion of issues and product performance.

The West Tennessee AgResearch and Education Center is located at 605 Airways Boulevard, Jackson, Tennessee. Upon arrival, follow signs to the w**d management research plots. For directions, or more information, call 731-425-4705.

W**d Tour Thursday June 20 - UT Crops News JACKSON, Tenn. – The University of Tennessee Institute of Agriculture will host the annual W**d Tour on Thursday, June 20 at the West Tennessee AgResearch and Education Center. The guided tour will feature 60 w**d management research tests in cotton, corn and soybean. W**d Tour runs from 9 – 11:...

Nitrogen loss potential in wet corn fields
By Nutifafa Adotey, Soil and Nutrient Management Extension Specialist on Jun 03, 2024 02:56 pm

From late April and throughout the month of May, many parts of Middle and West TN have received persistent rainfall that is well above the average for this period. These rains have produced persistently wet soil conditions and have coincided with sidedress N fertilizer application where most or all of the recommended N is applied. With this much rain, there is potential for N loss.
Generally, surface-applied unincorporated urea-based fertilizers, are susceptible to N loss via ammonia volatilization, denitrification, surface runoff, and leaching. However, the potential for N loss through denitrification and leaching are of special concern with during periods of excess rainfall and saturated soils.
Leaching involves the movement of nitrate-N (NO3–) with water below the root zone. Nitrate is water soluble, loosely bound to the soil, and therefore susceptible to leaching once the soil is saturated. Soil nitrate that moves below 4 feet is unrecoverable by most crops. Leaching is a greater risk if excessive rainfall occurs shortly after N fertilizer application, when the concentration of nitrate in the soil is high. Soil properties such as texture, structure, bulk density and depth to restrictive layers play major roles in leaching potential. In fine-textured soils with slow percolation, N loss via leaching may be negligible; however, in coarse textured soils where water percolates freely, 20 percent of applied N can be lost by leaching. Since most of the soils throughout Middle and West TN are not coarse-textured, the loss of N via leaching may not be substantial.
In contrast, denitrification is the conversion of nitrate into nitrous oxide (N2O) or dinitrogen gas (N2) when the soil is ponded continuously for at least 2 days. The gases produced during denitrification escape into the atmosphere and reduce the amount of N available for plant uptake. The rate of denitrification is greater in soils containing residue, which serve as food sources for the microbes. Depending on soil properties and environmental conditions, N loss via denitrification may account for 5-25 percent of the total N applied.
In saturated conditions, the dominant N-loss pathway for our soils will be denitrification. So, how would you estimate the amount of N loss as a result of denitrification from your field? The estimate will depend on the nitrogen source applied, the soil temperature at application, the amount of applied N in the nitrate form, and how long the soils have been saturated. Research at the University of Nebraska (click here), provides information on the proportion of applied N that would be in the nitrate form over time. Application of urea ammonium nitrate would result in more nitrates being present when compared to urea if application was made a few weeks prior to flooding or saturated soil.

What should you do now? Corn that appears yellow in a temporarily flooded field does not indicate all of the N has been lost or that the crop is deficient. Most of the N may still be still present, especially for sidedress N applications. The narrative is quite different for fall or winter applications, where denitrification loss will be higher considering most of the N is in nitrate form. Producers who applied all their N in the fall, winter, or early spring should make plans to apply additional N if needed.

utcrops.us3.le5efb59851