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C.O.R.N. Newsletter : 2015-17
Wet Weather: Flooding, Poor Nodulation, and Disease Concerns
The forecast for the coming week is for continued rain and in many cases this will fall on already saturated soils across the northern and west central part of the state. This is going to be tough on soybeans. Here is a guide to help differentiate among some key problems when these types of weather events occur.
1. Flooding: In fields that have had standing water for >48 hours, you’ll notice stunted soybeans and a smell as you approach the “drowned” out areas. When you dig the roots up, they may or may not be brown but the trick is that the outer layer of the root tissue, the cortical cells, can be easily pulled off leaving the white center of the root or root stele. The roots almost look like rat tails.
When plants are completely underwater for approximately 24-48 hours under high temperatures (>80°F), they will likely die. Plants respire more under high temperatures, oxygen is depleted, and carbon dioxide builds up suffocating the plant. Cool, cloudy days and cool, clear nights increase the survival of a flooded soybean crop. If the waters recede quickly and the plants receive some light rain, they can recover.
2. Poor nodulation: Yellow soybeans that can also be somewhat stunted – is often indicative of poor nodulation (see picture). Nodules are the small knots found on roots, often near the top of the root system. Nodules are the result of a symbiotic relationship between soybean and bacteria (Bradyrhizobium japonicum). These bacteria convert nitrogen into a form that is usable by the soybean plant.
Nodulation is reduced in wet soils. Soybeans at the V2 growth stage when grown in saturated soil for two weeks retain the ability to recuperate nodule function when normal (aerobic) conditions are restored. To determine if a nodule is actively fixing nitrogen (i.e., converting nitrogen to a usable form), split the nodule with your fingernail and examine the inside. If the inside of the nodule is pink or red, nitrogen is being fixed.
3. Disease: Flooded and saturated soil conditions will also provide the optimum conditions for the water molds that are common across the state. In these cases, the whole roots are brown, sometimes with dark brown lesions on the roots, and the tissue can be brown to tan. Both Phytophthora sojae and Pythium are contributing to this problem. Once the soybeans are at the V2 growth stage or greater, the protection from the seed treatment is gone and we are relying on the soybean plants’ defense system to mitigate the damage. For these areas in Ohio, the Rps genes for Phytophthora will only protect a few of the plants; we are relying on the partial resistance (field resistance, tolerance) part of the package.
What can you do for these, wait. When dryer weather returns the roots will re-establish. Anne has had some samples when dug up and mailed to Wooster, actually grew new roots during the transit. The roots just need some oxygen to get moving again. Check your drainage, these are excellent opportunities to see where some improvements can be made.
Henshaw, T.L., R.A. Gilbert, J.M.S. Scholberg, and T.R. Sinclair. 2007. Soya bean (Glycine max L. Merr.) Genotype response to early-season flooding: I. root and nodule development. J. Agronomy & Crop Science 193:177-188.
Sullivan, M., VanToai, T., Fausey, N., Beuerlein, J., Parkinson, R. and Soboyejo, A. 2001. Evaluating on-farm flooding impacts on soybean. Crop Sci. 41:93-100.
Concerns for N Loss in Corn from Recent Storms
Some parts of Ohio have recently experienced heavy rains, especially the northern part. Producers in these areas may have concerns about nitrogen loss in corn fields. Nitrogen losses occur by two main pathways: denitrification (gaseous loss of N) and leaching of nitrate from soil through water leaving the tile line or into groundwater. There is no tool or test that can tell how much has been lost. An estimate can made on the loss potential, which is based on N source, time of application, soil temperature, and number of days that soils have remained saturated.
Most nitrogen that is lost from a field is in the nitrate form during wet conditions. Time of transformation to nitrate is dependent on the type of N fertilizer applied. Anhydrous ammonia is less susceptible to loss since it converts to nitrate rather slowly. Urea-ammonium nitrate (UAN) solution has about 25% as nitrate at application time has a greater risk for loss than anhydrous.
Soils have been warm enough that some transformation to nitrate may have already occurred this year depending on application date. However, the nitrate N will not be lost by denitrification unless soils have remained saturated long enough. Risk of loss is minimal for soils that remain saturated for one day, moderate risk for two days of saturation, and a substantial risk for three or more days of saturated conditions. Standing water is evidence of saturated soils, but even soils without standing water are considered saturated if an individual cannot walk across without making footprints.
Since there are no absolute tests that can tell the N status a point system developed years ago by the University of Minnesota and modified to Ohio conditions has been useful. This system asks a series of questions and assigns a point value depending upon the answer. The probability of a response to additional N increases with more points. The questions and points are given below:
FACTOR 1: What N product was used?
Anhydrous ammonia with N-Serv 2 points
Anhydrous Ammonia 3 points
Other fertilizer banded 4 points
Other fertilizer broadcasted 5 points
FACTOR 2: When was the majority of the fertilizer N applied?
After April 20 3 points
Before April 20 5 points
FACTOR 3: What has been the field soil moisture status the past month?
Normal soil conditions 1 point
Wet soils 3 points
Standing water/saturated soils 4 points
FACTOR 4: What is the crop's current condition?
Green plants > 12" tall 1 point
Green plants < 12" tall 2 points
Chlorotic plants < 12" tall 3 points
Chlorotic plants > 12" tall 5 points
Total the score for the four factors and use the following guidelines:
Less than 11 No supplemental N recommended
11‑16 Evaluate again in 4-7 days
17 or more Add an additional 40 or more lbs. N/acre
The "re‑evaluation" option is only viable until you no longer have side dressing options. Illinois research from the 1990’s found that 50 lb. N/acre as a supplemental N rate was satisfactory for a wide range of conditions. While a total score of 17‑18 would merit a 40 lb./acre N recommendation. A total score of more than 18 may require a higher N rate. Losing 100% of the N fertilizer applied via denitrification or leaching is extremely unlikely and so a reapplication of the total amount of N for the season is not recommended.
Rootworm Hatch is UnderwayAuthor(s): Andy Michel
Last week, Larry Bledsoe from Purdue University reported that corn rootworm hatch occurred on June 3 (seehttp://extension.entm.purdue.edu/pestcrop/2015/Issue11/). With the exception of 2012, this seems to be in line with past few years. The bad news is that these young larvae will start to munch on the developing corn roots. The good news is that the heavy recent rain we are receiving will help saturate the soils. This heavy moisture will tend to increase mortality of these very small larvae. How much mortality remains to be seen, and, although this can severely impact rootworm populations, feeding can still be observed. There are good management tools to protect against rootworm feeding, including transgenic hybrids. As most are aware of, rootworm resistance to some Bt proteins has occurred in parts of the Western corn belt. We have not seen any substantial evidence of resistance in Ohio. Regardless of your rootworm management tactic, it is always a good idea to dig roots later in July after larvae development is complete to determine how well the product performed.
West Central Ohio Precision Agriculture Day: Combine and Drone TechnologyAuthor(s): Amanda Douridas
Please mark your calendars for the Precision Agriculture Day: Combine and Drone Technology which will be held Friday, August 21, 2015 at the Champaign County Fairgrounds in Urbana, OH. This event will feature presentations on decision agriculture, aerial imagery, utilizing field data, nutrient management, My John Deere and MyShed-Case IH. Some of the presenters include Dr. John Fulton, the new OSU specialist in precision ag technology, Ohio Farm Bureau, Integrated Ag Services, and a panel of farmers utilizing aerial imagery technology. Demonstrations from Case IH, John Deere, Lexion and New Holland dealers on combine setup for harvest will take place in the afternoon. Live drone flying demonstrations will also occur during the day.
This regional event is open to the public and was organized by the OSU Extension office and Farm Bureau office in Champaign County. We would like to thank Farm Credit for sponsoring lunch. We are currently looking for one breakfast sponsor ($250) and exhibitors ($150) to support the event. If you are interested in being a sponsor or exhibitor, please visit http://go.osu.edu/agevents for the sponsorship letter and form or contact Amanda Douridas at (937) 484-1526 or email@example.com. Sponsorship is due by July 1st to be included on the promotional flyer. Final details and registration information will be available in July.
Western ARS Agronomy Field Day, July 15thAuthor(s): Harold Watters, CPAg/CCA
The Western ARS Agronomy Field Day will be held July 15, 20015, with registration at 8:30AM until 9, then end the day at 3PM. The farm is located at 7721 South Charleston Pike, South Charleston, Ohio. The Western Agricultural Research Station is the University research center for agronomy in western Ohio. This site carries a significant load of work on soils and conditions that closely resemble much of western Ohio cropping systems. Join us to learn how to improve conditions on your farm.
The field day begins with morning in-field sessions from 9:00 a.m. until 12:00 p.m. This will feature three 1-hour talks and visits in the field at the researchers plots.
· Anne Dorrance to discuss reducing questionable inputs for increased profits. Profit is the key word in these times.
· John Fulton will review and show his work on plant response with precision planters looking at seedling depth and hydraulic down pressure.
· With Laura Lindsey we will view trials of micronutrient foliar applications to soybeans.
Lunch will be served at noon in the Western Ag Research Station’s air-conditioned conference room. You will have time to visit and ask more questions as you please.
For the afternoon we will provide a wagon tour of other projects on the station. We will make four one-half hour stops with speakers:
· Steve Culman – P and K fertilization Trials in Ohio Over Nine Years
· Alex Lindsey – Cover Crop Interseeding into Emerged Corn
· Andy Michel & Ron Hammond - Issues with Seed corn maggot and Corn Rootworm
· Peter Thomison - Exploiting Hybrid x Management Interactions for Higher Yields
Pre-registration is requested by July 10th to get a count for lunch from Rudy’s BBQ, the cost is $20 per person payable at the door. Contact Harold Watters Extension Field Specialist at 937-599-4227, firstname.lastname@example.org or Joe Davlin Western farm manager at 937-462-8016, email@example.com to register.
We thank the Ohio Soybean Council for their support of the Western Agronomy Field Day. Again the location is the OARDC Western Agricultural Research Station at 7721 South Charleston Pike, South Charleston, Ohio 45368 on SR 41 between Springfield and South Charleston, watch for signs. See you on July 15th.
CCA continuing education credits will be available.
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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