Published on Wednesday, March 01, 2017
When it comes to wheat management, there are many decisions that can be made in the fall, such as herbicides, tillage, and row spacing, that ultimately influence the success of your crop. Once we reach the spring and summer months, nitrogen (N) management decisions such as forms and inhibitors, as well as fungicides and herbicides become top of mind. With lower commodity prices it’s even more critical to evaluate wheat management options to increase our bottom line. Over the past few years, Beck’s Practical Farm Research (PFR)® team has tested many of these management options across multiple locations in hopes of helping farmers make more informed decisions.
Row spacing and tillage can influence the amount of weed pressure in a field. In a conventional-till scenario, a fall herbicide application may not be necessary. In no-till fields, however, fall and spring applications may be warranted. Publications such as the 2017 Weed Control Guide by The Ohio State University Extension1 are great resources for winter annual control ratings. According to this guide, Finesse® provided control of 90 percent of common chickweed, henbit, pennycress and shepherds purse, and provided 80 percent control of marestail (non-group 2 resistant). Tribenuron + thifensulfuron, the active ingredients in Harmony® Extra SG, provided the same level of control with exception to horseweed (non-group 2 resistant), which was only controlled by 70 percent. The application of PowerFlex® offered 60 percent control of horseweed, 70 percent control of henbit, and 80 percent control of shepherds purse. Herbicide products like Finesse offer broader weed control of winter annuals compared to other herbicides. Beck’s two-year data at the Southern Illinois PFR site has shown that Finesse resulted in a greater yield reduction compared to applications of metribuzin, Harmony Extra SG and PowerFlex when applied in the fall (Figure 1). According to the 2017 Weed Control Guide, however, Finesse does offer greater weed control compared to other products. Selecting a product that controls your weed spectrum is crucial to preventing yield loss.
Figure 1. Southern, IL 2013/2014 herbicide wheat injury.
One of the first management practices you should consider in the spring is determining the amount of tillers at Feekes 3 (Figure 2). For maximum yield potential, many wheat guides such as University of Kentucky Wheat Management Guide suggest that the optimum number of tillers at Feekes 3 should be between 70 and 100 tillers/sq. ft.
Figure 2. Wheat Growth and Management Practices from the Cooperative Extension Service, University of Kentucky College of Agriculture
If tiller counts are greater than 70 tillers/sq. ft., the amount of nitrogen (N) applied at Feekes 3 should be lowered. If tiller counts are less than 70 tillers/sq. ft., a larger amount of N should be applied at Feekes 3 with the remaining balance of N applied at Feekes 5. To determine the correct rate of N, count the number of tillers per plant. If plants have zero to two tillers, 50 percent of the N should be applied at Feekes 3 with the remaining 50 percent applied at Feekes 5. If the plant has three to four tillers, apply 40 percent of the N at Feekes 3 and the remaining 60 percent at Feekes 5. Plants with five or more tillers should receive 100 percent of the N at Feekes 5. The risk of too much N at Feekes 3 may result in excess tillers, but excess N may promote growth too rapidly which could put the plant at risk if a late freeze occurs. Split applications are beneficial as they reduce the risk of the plants running out of N if Feekes 5 is delayed. To learn more about tiller counts and Feekes 3 N applications, check out this video from PFR agronomist and location lead Jonathan Perkins. You can also check out this video to learn more on how to identify the different wheat growth stages and how those stages can influence herbicide applications.
Economic Optimum Nitrogen Rate (EONR)
When it comes to Economic Optimum Nitrogen Rate (EONR), soil moisture, yields, soil types and price of UAN can all influence the EONR. At the Kentucky PFR site, the EONR ranged from 96 to 104 units of UAN (Figure 3). At the Southern Illinois site however, this number ranged from 108 to 119 units of UAN (Figure 4). The Kentucky study was conducted in a conventional-till scenario which lowered the total N requirment. This is because tillage results in less residue, which decreases the amount of N needed due to it’s influence on C:N ratio. At the Southern Illinois site, this two-year study was conducted in a no-till situation, resulting in a greater EONR. It is important to note that this two-year data captures results from one very wet year, which led to saturated soils and an increased opportunity for volitilization. Because the UAN was applied on the surface of soils with excess moisture, the chance of N loss was very high in 2016. If we continue to experience wet springs with wheat yields over 100 Bu./A., the EONR may continue to rise.
Figure 3. Economic Optimum Nitrogen Rate (EONR) multi-year data set from KY conventional-till.
Figure 4. Economic Optimum Nitrogen Rate (EONR) multi-year data set from Southern IL no-till.
Once your EONR is calculated, the next question you need to ask yourself is what form of N should you use? The best answer to this question depends on your own operation and preference. To increase your net return, you must remember that, whether using a UAN or urea application, the most important thing is proper management. In Beck’s two-year, multi-location study, a split application of urea at Feekes 3 and Feekes 5 resulted in the greatest return on investment (ROI) (Figure 5). Split applications of urea not only promote early growth but also reduce the chance of N loss later in the season.
Figure 5. Multi-year, multi-location net return data from the urea nitrogen management study.
When it comes to UAN, a split application at Feekes 3 and Feekes 5 also resulted in the greatest net return over two years and across multi-locations (Figure 6). This further supports how crucial N management is to a high yielding wheat crop.
Figure 6. Multi-year, multi-location net return data from the UAN nitrogen management study.
With both urea and UAN, we have seen an increase in yield with a split application or a protected form or inhibitor. If 100 percent of the N is applied at Feekes 3, a protected form or inhibtor is crucial. While in some cases this resulted in higher yields than the split applications, the split applications of urea or UAN resulted in the greatest net return. Split applications promote tillering at Feekes 3 and also reduce the chance of N loss with the Feekes 5 application. Wheat crops experience their highest demand for N after Feekes 5, as shown in Figure 7. Therefore, these split applications reduce the chance of N loss, ensuring the plant will have N available later in the season when it needs it most.
Figure 7. Wheat growth curve from the Cooperative Extension Service, University of Kentucky College of Agriculture publication: A Comprehensive Guide to Wheat Management in Kentucky, ID-125. Original publication date: 2009.
Growth Regulator Applications
A popular saying among wheat farmers is “if you’re not lodging some wheat than you’re not pushing it hard enough.” We all know the drawbacks from having down wheat, but what if we could push the N rate further but still reduce the chance of lodging? Palisade® EC is a plant growth regulator that helps shorten the internodes, reducing the chance for lodging. When applied at both 120 and 140 units of UAN, it resulted in an increase in yield. However, when 120 units of UAN was applied, only the 6 oz. rate resulted in a positive ROI. As N rates increased to 140 units of UAN, both the 6 oz. and 12 oz. rate of Palisade resulted in a positive ROI. This study showcased that Palisade is an excellent product for intensively managed wheat and that 12 oz. may be needed if using over 140 units of UAN.
Figure 8. Palisade® EC 2016 multi-location data. Test weight and Bu./A. were corrected to 13.5% moisture.
Wheat prices have been down the past few years, resulting in farmers looking for ways to cut costs. One place they typically look at first when cutting costs is on fungicide applications such as Prosaro® 421 SC. However, Beck’s PFR data suggests that applying products like Prosaro late in the season is actually like having an insurance plan on your crop. The main diseases controlled with late applications of a fungicide like Prosaro are Fusarium head blight or head scab. Even in years with low diseases pressure, Beck’s multi-location data still showed a $6.89/A. ROI (Figure 9). While Prosaro may not pay off every single year, if disease pressure does become an issue, it will reduce your chances of being rejected or docked at the elevator. To learn more about late season fungicide applications (when to apply and how to stage wheat), I suggest you check out this video.
Figure 9. Prosaro® 421 SC 2016 multi-location data. Test weight and Bu./A. were corrected to 13.5% moisture.
With lower commodity prices, it is more crucial than ever to find ways to increase your ROI. Just like any other crop, the right management practices can help increase yields. From something as simple as row spacing and tillage to herbicides and proper N management, there are a number of things we can do to have a successful wheat crop. Stay tuned for more wheat updates this spring!
Practical Farm Research (PFR)® is a registered trademark of Beck’s Superior Hybrids, Inc. Finesse® and Harmony® are registered trademarks of DuPont Pioneer. Palisade® is a registered trademark of Syngenta Group Company. Prosaro® is a registered trademark of Bayer Crop Science. PowerFlex® is a registered trademark of The Dow Chemical Company (“Dow”) or an affiliated company of Dow.
1Pub# WS16/Bulletin 789/IL15
Author: Joe Bolte
Categories: PFR, PFR Reports
Tags: PFR Report, winter wheat management, Joe Bolte
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