C.O.R.N. Newsletter: 2024-21

Before removing straw from the field, it is important for farmers to understand the nutrient value. The nutrient value of wheat straw is influenced by several factors including weather, variety, and cultural practices. Thus, the most accurate values require sending a sample of the straw to an analytical laboratory. However, “book values” can be used to estimate the nutrient value of wheat straw. In previous newsletters, we reported that typically a ton of wheat straw contains approximately 11 pounds of N, 3.7 pounds of P₂O₅, and 29 pounds of K₂O. According to the 2024 Second Quarter Fertilizer Prices Across Ohio bulletin https://u.osu.edu/ohioagmanager/2024/04/15/2024-second-quarter-fertilizer-prices-across-ohio/) and nutrient removal “book values”, one ton of wheat straw would remove approximately $14.12 of P₂O₅ & K₂O.

In addition to Table 1, you may also download and use this excel-based spreadsheet: https://stepupsoy.osu.edu/wheat-production/wheat-profitability-calculator to estimate profitability of wheat production with and without straw removal. In Tab 1 of the spreadsheet, enter your production costs or use our default values. Then, Tab 4 of the spreadsheet will estimate partial return of wheat production with and without straw removal. Several other cropping scenarios are also available for profitability comparisons.

Although N adds value, we do not give it an economic value in the form of fertilizer (as seen in Table 1). Within straw, N is in an organic form and will not immediately be available for plant uptake. The organic-N will need to be converted by microorganisms to ammonium-N (an inorganic form) before it is available for plant uptake – a process called mineralization. The rate of which mineralization occurs depends on the amount of carbon (C) and N in the straw (C:N ratio). The USDA reports a C:N ratio of 80:1 for wheat straw which means there are 80 units of C for every unit of N. Mineralization rapidly occurs when the C:N ratio is ≤ 20:1. At a C:N ratio of 80:1, mineralization will be much slower. (For comparison, corn stover is reported to have a C:N ratio of 57:1.) Rate of mineralization is also influenced by soil moisture and temperature. Since mineralization is a microbial-driven process, mineralization will be slowed (halted) in the winter when temperatures are cold. Thus, no N credit (i.e., value) is given for wheat straw since it is not known when the N will mineralize and become available to the following crop.

In addition to N, removal of straw does lower soil K levels. If straw is removed after heavy rainfall, some of the K may have leached out of the straw, lowering the nutrient value. However, a soil test should be done to accurately estimate nutrient availability for future crops. Besides providing nutrients, straw has value as organic matter, but it is difficult to determine the dollar value for it. 

The annual Western Agronomy Day will be held on Wednesday, July, 17 from 9:00 a.m. to 3:00 p.m. at the Western Agricultural Research Station (7721 South Charleston Pike, South Charleston, Ohio 45368).

The morning session will start with Dr. Horacio Lopez-Nicora discussing soybean cyst nematode and which soybean diseases to look out for this year.  Then we will get a look at the much-anticipated Battle of the Belt Corn and Soybean Competition with Dr. Laura Lindsey, Taylor Dill, and Dr. Osler Ortez.  We have one year of data under our belt to share, as well as look at this year’s crops.  Dr. Pierce Paul will be our last stop before lunch, to discuss vomitoxin management and corn disease forecast for 2024.

After lunch we will visit the herbicide interaction demo with Tony Dobbels to look at how different herbicides work on weeds and crops.  Our last stop will be with the OSU Department of Entomology for a hands-on pest demonstration. 

Please RVSP by July 10, 2024, to davlin.1@osu.edu or call 937-462-8016 for an accurate lunch count.  Lunch will be supplied by Lyons Catering.

With Ohio’s wheat crop coming off early this year, those who may need additional forage have an excellent opportunity for acres to be available where annual forages can be planted and grazed or harvested yet this year. For those wanting acres available for multiple grazings or cuttings later this summer, a summer annual such as sorghum-sudangrass may be the logical choice. However, if the forage need is not immediate, but rather a single grazing or cutting in late summer or fall is preferred, based on our experience in Fairfield County with oats planted after wheat harvest over the past 20+ years, oats are a low cost yet high quality feed alternative. In fact, if planted most any time in July or August, there’s an opportunity to grow anywhere from two to five tons of forage on a dry matter basis while investing little more than the cost of 80-100 pounds of oats, 45+/- pounds of nitrogen, and some time and labor.

With wheat harvest so early this year there may be the urge to get a second crop forage planted immediately. If planting a summer annual such as sorghum-sudangrass an earliest possible planting date is important. However, over the years we’ve found it’s NOT important to rush to get oats planted as soon as possible after wheat harvest. In fact, since oats typically result in a single cutting and offer little regrowth potential, our experience has been that we get a greater yield and higher quality feed if we wait until the end of July or very early August to plant oats for forage. Without getting into a science lesson, it seems the oats prefer the cooler average daily temperatures we typically experience beginning in August, and they are less likely to push out a seed head, but remain vegetative until extremely cold temperatures shut them down completely sometime in December.

Not only does an August 1 planting date seem to offer more yield and higher quality oats, but it also allows ample time to complete harvest, apply manure, and control any perennial weeds and volunteer wheat that might be present. Considering the continuing challenges with marestail, the time and effort spent post wheat harvest and pre-oat planting would be valuable for controlling this and other weeds.

Based on experiences with summer planted oats since 2002, consider these management suggestions:

• Optimum planting date for oats from the perspective of yield is not until late July or the first of August. Early August plantings also have resulted in the highest total amount of TDN produced per acre. Later plantings will be slightly higher in quality, but typically not enough so to offset the yield advantage of an August 1 planting. While being more conducive to a mechanical harvest in early Fall, planting in early to mid-July reduces both yield and quality. The earlier oat plantings also have exhibited more susceptibility to rust.
• Since fall harvested oats for forage have shown susceptibility to crown rust. A timely application of fungicide can prevent crown rust and improve oats digestibility.
• Regardless the planting date, or variety, no-tilled seeding rates of from 80 to 100 pounds of oats have consistently resulted in optimum forage yields.
• Optimum nitrogen application rate has been 40 to 50 pounds per acre. This application not only produces the highest yields, but at current values of nitrogen, it’s also the most cost effective rate. Higher rates of nitrogen actually depressed yields in our 2008 plots.
• Over the years, many growers have been successful using bin run ‘feed’ oats originating in Canada. Most of the concerns with utilizing ‘feed’ oats are obvious: no germination test, and the potential for bringing some weed seed onto the farm. Another problem we experienced once was that a few of the Canadian oats in the “feed bin” were apparently winter oats. After getting started in the fall, they went dormant over winter, and then elongated in the spring much like winter wheat does after breaking dormancy.
• The optimum combination of productivity and quality of August planted oats arrives 60 to 75 days after planting. Apparently due to the heat, oats planted in July mature more quickly and thus, rapidly decline in quality beginning 50 to 60 days after planting in most years.
• Oats harvested 50-60 days after planting and while still in the boot stage of maturity may offer some regrowth that could be grazed.
• A weed control application of glyphosate is a necessary and cost effective practice prior to oat planting. If glyphosate resistant marestail is present, a broadleaf killer needs to be included and the proper delay in planting according to the label of that product observed.

An additional advantage observed when using oats for an annual forage crop is the opportunity to capture the total tonnage produced with a single cutting harvest if grazing is not an option. Crops that require multiple mechanical harvests increase costs of production significantly.

If mechanical dry harvested forage is the goal, oats can be planted in early July, and have produced 2.5+/- tons DM by mid September.

While of lesser quality, oats planted in early July have produced 2.5+/- tons DM by mid September.

As oat forage harvest options typically beginning by November are considered, grazing provides the most effective and affordable alternative. In 2002 one Fairfield County producer strip grazed oats all winter and actually began the calving season on them before the oats ran out in mid-March.

Dry baling oats in the fall has been done around Ohio, but it’s a challenge considering that once cut, oats will dry less than half the rate of grass hay. Cut in November, it typically means at least two weeks or more required to cure them for dry hay harvest. Wet wrapping them is an expensive alternative. Using an in-line bale wrapper/tuber is a less expensive per ton than individually wrapped bales if the equipment is available locally.

Oats won’t die until temperatures have been in the mid 20’s for several hours. That means they’ll still be green and alive in December most years in Ohio. When they finally freeze, and if it’s not a wet winter, growers may be able to let them die and dry while standing, get a few days of dry or frozen weather in January, mow them, rake them, and quickly bale them after they’ve essentially cured while standing.

In Canada, growers have sprayed their oats with glyphosate and let them begin to dry while standing. After a few weeks and at a time when they get a dry week, they mow, rake and bale them all in a day or two. Locally, that’s been done once that I know of which allowed the oats to be baled in late December and January.

If grazing the standing oats is not an opportunity, perhaps chopping and ensiling oats is the best alternative for harvest. This offers several advantages over baling or wet wrapping. Obviously, the issue of curing the plants for dry harvest becomes a moot point. Chopping and ensiling in either a permanent structure or bags is also likely less expensive than wet wrapping individual bales. Perhaps even better, as detailed in the past in this publication, chopped forages are 30 to 60% more digestible than long stem forages.

Admittedly chopping and ensiling is likely more expensive than rolling dry hay, but when you consider you get essentially no storage losses, the timeliness of harvest that is afforded, and the more digestible feed that results, it’s a good alternative. And if you’re able to bunk feed the chopped and ensiled oats, there will be minimal “bale ring” feeding losses experienced.

During the winter of 2013 Ohio Forage and Grassland Council Annual Meeting, I was invited to share the following presentation that includes a number of photos about our past experience of growing oats late in the summer for forage. Oats, planted after wheat harvest, into the stubble, are indeed, a consistently productive and high-quality forage alternative!

Episode 14 of Battle for the Belt is now available: https://www.youtube.com/watch?v=X9spGf3GBY0

In Episode 14, we get a weather update from Dr. Aaron Wilson, Ag Weather and Climate Field Specialist. Please see his article called “Weather Extremes Abound” in this newsletter for an update.

What’s happening in the field?

In the past week most of the state received some needed rainfall. However, the Northwest region of the state experienced storms and heavy rains through the middle and end of the week. These rains prohibited our research team from taking field notes. Before the rain began, the fifth and final planting date was established at the Northwest location on June 24^th (Table 1).

At the Western location, soybeans planted on date one (March 25), two (April 16), and three (May 6) were all in the reproductive stages. Planting date one and two were at beginning pod (Table 2.). If you have earlier planting dates, especially as we come into the fungicide and insecticide spray application window for the earlier planted fields, it is time to scout for disease incidence and severity to determine if a fungicide application may be necessary. Corn planted on date one (March 25) reached R1 for all relative maturities. For corn planted at an early planting date and getting close to VT/R1, it is important to scout your fields. R1 is the optimal application window for fungicides in corn. Scouting for disease incidence and severity and location of the disease on the plant is necessary for an effective fungicide application. Many diseases may stay on the lower leaves of the canopy but are highly dependent on the environment. If the weather continues to be hot and humid, and you have a susceptible hybrid and a field history of disease, you may consider an application. At the Western location, the disease rating notes began and there were low levels in both incidence and severity of gray leaf spot and tar spot on the ear leaves of these hybrids. If you want to look into scouting for corn and soybean diseases more, please visit https://cropprotectionnetwork.org/. This website is informed by Extension specialists throughout the U.S. and has tools and scouting guidelines for many different diseases in agronomic crops.

At the Wooster location, soybeans planted on date one (April 22) were at R2 and are currently the only planting date in either crop that has entered the reproductive stages. Septoria brown spot has been identified on soybean plants at this location in the ultra-early planting date. While typically not resulting in significant yield reduction, it is advised to closely scout fields and monitor the disease progression to minimize any potential impact on yield. At this location anthracnose in corn was also identified, which can be common for the northeastern side of the state. With Anthracnose, the first leaves will die off and the disease stays within the lower canopy, but in severe cases can be seen in the newest leaves. In Ohio, this disease is not generally a yield concern.

This year’s crop has progressed very quickly in comparison to last year or a “normal” year, be proactive and get into your fields early to evaluate disease and check the stage of the crop to time foliar applications.  It is important to apply foliar products at the proper crop growth stage based on scouting, not calendar date.

*Data not collected the week of June 24 due to heavy rainfall events.

As we near the end of our slug monitoring project in many counties (monitoring for 6 weeks after plant), we continue to observe warm temperatures, and as a result slug numbers remain low under the shingle traps. Low numbers don’t necessarily mean slugs are no longer around, they mean the slugs are not as active and plants are likely outgrowing feeding damage. If you are observing defoliation on your soybean plants, use the guide provided in Figure 1 to determine if treatments may be necessary. Soybean defoliation thresholds are dependent on the plants growth stage (Figure 1). For instance, plants from V1 (first trifoliate) – R2 (full bloom) have a 30% defoliation threshold before yield loss becomes an issue. In Ohio, many soybean fields are past VE (cotyledon emergence) – VC (unifoliate leaves unrolled), which is most susceptible to slug damage, because the growing point of the plant is within the emerging cotyledons. If your plants succumbed to slug damage at the VE – VC stage, it may be necessary to replant. If you decide to replant with no other treatments against slugs, keep a close eye on the seedlings because slugs remain in the field year-round and may continue feeding on the newly planted seeds.

For advice on soybean replant decisions, view our previous newsletter article:

https://agcrops.osu.edu/newsletter/corn-newsletter/14-2021/soybean-stand-evaluation-and-re-plant-decisions

Bait Treatment Options
As mentioned in previous newsletters, there are not many options available for slug management in Ohio. One option is baits containing metaldehyde or iron phosphate. Before applying baits, it is important to confirm slugs are causing the defoliation in your field. Slugs are nocturnal, making them difficult to spot during the day (especially with the increasing heat). To get a feel for your slug population look for the slugs by carefully examining the soil surface, brushing aside residue and debris. You can put down square foot sections of plywood at a few locations in the field (marked with flags) and check under them periodically in the morning. Unfortunately, we do not have a threshold recommendation for how many slugs is too many, but monitoring the population will give you a feel for whether the problem is increasing or decreasing. If you decide an application is necessary, apply the baits in dry weather, when rain is not in the forecast to avoid the pellets breaking down. 

Metaldehyde (3.24 and 4%) remains the most effective bait treatment to date. Concentrations are most effective when applying 10 pounds per acre for soybeans and 25 pounds per acre for corn (spread pellets at a rate of 5 – 12 pieces per square foot). Metaldehyde is labeled in Ohio for both crops, but not labeled for both crops in all states, so be sure to check the label before application. An alternative to metaldehyde is iron phosphate, but it is not as effective. The advantage of iron phosphate is it is approved for use in organic crops.

For more information on slug management, visit our field crop slug factsheet at https://aginsects.osu.edu/sites/aginsects/files/imce/Slugs%20on%20Field%20Crops%20_%20Ohioline.pdf

Ohio Monitoring Update
The number of counties monitoring slugs in Ohio for the multi-state project funded by the United Soybean Board is starting to decrease, as many counties have already reached the monitoring expectation of monitoring for 6 weeks after plant. 

The map below shows the average number of slugs found under the shingle trap in each county from June 24^th – June 30^th (Figure 2). With the high temperatures, the average number of slugs in the majority of counties decreased. Seneca county had the highest average of 10.2 slugs/shingle over the past week, followed by Allen county with 0.8 slugs/shingle. The majority of counties in Ohio continue to report low numbers of slugs under the shingle traps; however, slug activity varies greatly from field to field, and all no-till fields planted recently should be scouted for slugs – especially fields that are newly planted or in the VE – VC growth stage.

Slug Monitoring in Ohio
June 24^th – June 30^th