Horseweed (marestail) control options in fallow prevent plant fields

Source: Christy Sprague, Michigan State University

The challenging conditions this spring have left many fields unplanted. Glyphosate- and multiple-resistant horseweed (marestail) dominates a majority of these fields. Horseweed and other weeds in these unplanted fields need to be controlled prior to setting seed to prevent future weed problems. To help determine some of the more effective options for horseweed control, we sprayed several treatments two weeks ago on 2 feet tall horseweed. Common lambsquarters, common ragweed and prickly lettuce were also present in this field. Below is a compilation of pictures of these treatments and a summary of the results.

Horseweed control results

Roundup PowerMax (glyphosate) alone was ineffective at controlling a majority of the horseweed plants in this field (Figure 1A), indicating this population is highly resistant to glyphosate. Glyphosate-resistant horseweed is extremely common in many Michigan fields and glyphosate alone should not be used. The addition of 2,4-D ester at 1 pint per acre (pt/A) or 1 quart per acre (qt/A), Enlist One at 1 pt/A or Clarity (dicamba) at 1 pt/A to Roundup PowerMax improved horseweed control. However, controlling horseweed with these treatments only ranged from 60–70% 14 days after treatment (Figure 1B). These treatments will not likely result in complete control of horseweed.

The addition of 2,4-D or dicamba also improved common lambsquarters and common ragweed control over Roundup PowerMax alone. While these may be some of the more inexpensive treatments, they were not the most effective and caution should be taken if 2,4-D ester or any of the dicamba formulations are used. Off-target movement by drift or volatility, especially under high temperature conditions and when sensitive crops are in the area, can occur these herbicides.

Horseweed control 2
Figure 2. Glyphosate-resistant horseweed control with (A) Liberty (glufosinate) at 32 fl oz/A plus AMS and (B) Sharpen at 1 fl oz/A plus Roundup PowerMax at 32 fl oz/A plus MSO plus AMS, 14 days after treatment. Photo by Christy Sprague, MSU.

The most effective treatments to control glyphosate-resistant horseweed were Liberty (glufosinate) at 32 fluid ounces per acre (fl oz/A) plus AMS (Figure 2A), or Sharpen at 1 fl oz/A or 2 fl oz/A plus Roundup PowerMax at 32 fl oz/A plus MSO plus AMS (Figure 2B). These treatments resulted in greater than 95% control of horseweed, common lambsquarters, common ragweed and prickly lettuce. A higher rate of Liberty (glufosinate) at 43 fl oz/A can also be used.

Initial control of glyphosate-resistant horseweed with Gramoxone 3L (new formulation) at 2.67 pt/A plus surfactant was 80%. However, by 14 days after treatment, horseweed started to regrow (Figure 3). Controlling common lambsquarters, common ragweed and prickly lettuce ranged from 70–75%.

Horseweed control 3
Figure 3. Glyphosate-resistant horseweed control with Gramoxone plus surfactant, 14 days after treatment. Photo by Christy Sprague, MSU.

Two additional treatments we examined included disking and mowing. Mowing reduced overall weed biomass, however it also removed the primary growing point and as horseweed started to regrow, additional shoots were produced. If mowing, multiple passes throughout the season will likely be required. A onetime mowing would likely be more beneficial later in the season prior to flowering and seed set. Tillage or disking did provide good horseweed control, however it will likely take multiple passes to keep the fields clean throughout the season.

Additional considerations

All these treatments were applied under good growing conditions (plenty of moisture and heat) and resulted in good herbicide activity. As weeds continue to grow and begin to flower, the effectiveness of these treatments will likely be reduced. Additionally, depending on the weed species, there could possibly be new emergence later in the season.

Crop rotation restrictions also need to be considered when choosing one of these herbicide treatments for horseweed and other weed control. Sharpen, 2,4-D and dicamba all have residual activity and could cause injury to certain cover crops and winter wheat if rotation restrictions are not followed. Winter wheat should not be planted earlier than one month after applying dicamba or 2,4-D (Enlist One). Sharpen at 1 or 2 fl oz/A can be applied any time before planting winter wheat. There is a 70-day rotation restriction between Liberty applications and planting winter wheat. Consult individual herbicide labels.

What is the Nutrient Value of Wheat Straw?

Laura Lindsey, Ed Lentz, OSU Extension

Wheat harvest is now underway. What is the nutrient value of the straw? 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 values of wheat straw. In previous newsletters, we reported that typically a ton of wheat straw would provide approximately 11 pounds of N, 3 pounds of P2O5, and 20 pounds of K2O.

The nitrogen in wheat straw will not immediately be available for plant uptake. The nitrogen will need to be converted by microorganisms to ammonium and nitrate (a process called “mineralization”). Once the nitrogen is in the ammonium and/or nitrate form, it is available for plant uptake. The rate of which mineralization occurs depends on the amount of carbon and nitrogen 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 carbon for every unit of nitrogen. 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 is given for wheat straw since it is not known when the N will mineralize and become available to the following crop.

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

Ohio Corn, Soybean and Wheat Enterprise Budgets – Projected Returns for 2019

Source: Barry Ward, Leader, Production Business Management & Director, OSU Income Tax School

Production costs for Ohio field crops are forecast to be largely unchanged from last year with slightly higher fertilizer and interest expenses that may increase total costs for some growers. Variable costs for corn in Ohio for 2019 are projected to range from $356 to $451 per acre depending on land productivity. Variable costs for 2019 Ohio soybeans are projected to range from $210 to $230 per acre. Wheat variable expenses for 2019 are projected to range from $178 to $219 per acre.

Returns will likely be low to negative for many producers depending on price movement throughout the rest of the year. Grain prices used as assumptions in the 2019 crop enterprise budgets are $3.60/bushel for corn, $8.20/bushel for soybeans and $4.25/bushel for wheat. Projected returns above variable costs (contribution margin) range from $150 to $308 per acre for corn and $144 to $300 per acre for soybeans. Projected returns above variable costs for wheat range from $102 to $202 per acre (assuming $4.25 per bushel summer cash price).

Return to Land is a measure calculated to assist in land rental and purchase decision making. The measure is calculated by starting with total receipts or revenue from the crop and subtracting all expenses except the land expense. Returns to Land for Ohio corn (Total receipts minus total costs except land cost) are projected to range from $23 to $182 per acre in 2018 depending on land production capabilities. Returns to land for Ohio soybeans are expected to range from $84 to $254 per acre depending on land production capabilities. Returns to land for wheat (not including straw or double-crop returns) are projected to range from negative $2 per acre to a positive $143 per acre.

Total costs projected for trend line corn production in Ohio are estimated to be $753 per acre. This includes all variable costs as well as fixed costs (or overhead if you prefer) including machinery, labor, management and land costs. Fixed machinery costs of $66 per acre include depreciation, interest, insurance and housing. A land charge of $187 per acre is based on data from the Western Ohio Cropland Values and Cash Rents Survey Summary. Labor and management costs combined are calculated at $69 per acre. Returns Above Total Costs for trend line corn production are negative at -$120 per acre.

Total costs projected for trend line soybean production in Ohio are estimated to be $518 per acre. (Fixed machinery costs – $52 per acre, land charge: $187 per acre, labor and management costs combined: $45 per acre.) Returns Above Total Costs for trend line soybean production are also projected to be negative at -$76 per acre.

Total costs projected for trend line wheat production in Ohio are estimated to be $488 per acre. (Fixed machinery costs: $52 per acre, land charge: $187 per acre, labor and management costs combined: $39 per acre.) Returns Above Total Costs for trend line wheat production are also negative at -$137 per acre.

These projections are based on OSU Extension Ohio Crop Enterprise Budgets. Newly updated Enterprise Budgets for 2019 have been completed and posted to the OSU Extension farmoffice website: https://farmoffice.osu.edu/farm-management-tools/farm-budgets

Estimating Wheat Yield With Stem Counts

Source: Dr. Laura Lindsey

Between planting in the fall and Feekes 4 growth stage (beginning of erect growth) in the spring, winter wheat is vulnerable to environmental stress such as freezing temperatures with limited snow cover, saturated soils, and freeze-thaw cycles that cause soil heaving. All of which may lead to substantial stand reduction.

However, a stand that looks thin in the spring does not always correspond to lower grain yield. Rather than relying on a visual stand assessment, farmers should estimate the yield potential of their winter wheat crop by counting stems, before deciding whether a field should be destroyed. An alternative method to evaluate wheat stand is fractional green canopy cover (FGCC). Fractional green canopy cover can be used to measure the canopy surface area using the mobile device application Canopeo. The app can be downloaded for free here: http://www.canopeoapp.com.

Figure 1. Measurement tool used to consistently count the number of stems in one foot of row.

Wheat Stem Count Methods: Wheat stems (main stem plus tillers) should be counted at Feekes 5 growth stage (leaf sheaths strongly erect) from one linear foot of row from several areas within a field (Figure 1).

 

 

 

 

 

Figure 2. Winter malting barley image analyzed for fractional green canopy cover with the Canopeo mobile device application.

 

Fractional Green Canopy Cover Methods: Fractional green canopy cover should be measured at Feekes 5 growth stage using the mobile device application, Canopeo (http://www.canopeoapp.com). The camera should be held at a height to capture three rows of wheat in the image (Figure 2).

 

 

 

 

 

After counting the number of wheat stems or measuring FGCC, Table 1 can be used to estimate wheat grain yield. For example, if an average of 51 stems is counted from one foot length of row, the predicted grain yield would be 100 bu/acre. Similarly, if the average FGCC measurement was 35%, the predicted grain yield would be 100 bu/acre.

 

 

 

 

Spring Herbicide Applications on Winter Wheat – Part 2 Labeled Herbicides

Source: Purdue University (Edited)

If weed infestations are severe enough to require a herbicide application, the use of liquid nitrogen fertilizer solution as a carrier is a popular option for applying herbicides and topdressing the wheat crop in a single pass over the field.  Caution should be taken when using a liquid fertilizer as a herbicide carrier as moderate to severe crop injury can result, especially in saturated conditions.  Many post applied wheat herbicide labels allow for liquid nitrogen carriers, but require different rates and types of surfactants than if the herbicide was applied with water as the carrier.  Table 1 includes precautions to be taken when applying wheat herbicides using liquid fertilizer as a carrier; further details and directions can be acquired from the herbicide label.

Another consideration growers should take into account when planning early spring herbicide applications is the plant back restrictions to double crop soybeans.  A large percentage of the herbicides listed in Table 1, especially those with activity on Ryegrass and Brome, have soybean plant back restrictions greater than the typical three month time period between spring applications and double crop soybean planting.  The soybean plant back restrictions greatly reduce the number of options available to wheat producers who double crop soybeans after wheat.  Refer to Table 1 for more specific plant back timing restrictions.Click Here For Complete Table

Spring Herbicide Applications on Winter Wheat – Part 1 Growth Stages

Source: Purdue University (Edited)

The winter is finally winding down and we are bound to have warmer days and spring in the near future. As we look towards the warmer weather there a few field activities that are going to start quickly, including winter wheat greenup herbicide applications and winter annual weed burndown applications in no-till fields. There are few things to keep in mind as these activities are added to the calendar. Many wheat producers, especially in the southern regions of Indiana will soon be or already are topdressing their wheat.  Those looking into topdressing need to also be scouting for weeds and determining if a herbicide application is necessary on any existing winter annual weeds.  The following information will outline winter annual weeds to look out for, weed scouting tips, crop stage restrictions, and herbicide recommendations.

Some common broadleaf weeds to scout for in your winter wheat are dandelion, purple deadnettle, henbit, chickweed, Canada thistle, and wild garlic.  These winter annual species that emerge in the fall can remain relatively inconspicuous through the winter and become competitive and troublesome during the spring if not controlled early in the spring.  Summer annual weeds such as ragweed will be of less concern in the early spring and will be outcompeted by the wheat crop if managed properly.  Grass weeds to be aware of and scouting for are: annual bluegrass, annual ryegrass, cheat, and downy brome.

Determining the severity of weed infestations in your wheat fields is key in determining the necessity of a herbicide application.  As with all agronomic crops, you should scout your entire field to determine what weed management practices need to be implemented and determine any areas of severe weed infestations.  Wheat fields that contain uniform infestations of at least one broadleaf weed and/or three grass weeds per square foot should be taken into consideration for a herbicide application to avoid yield loss and harvest interference problems.  Some fields that have less uniform infestations, but rather pockets of severe infestation should be managed to reduce weed seed production and future infestations.

When determining your herbicide program for spring applications, the stage of the wheat crop should be considered.  The majority of wheat herbicides are labeled for application at certain wheat growth stages and some commonly used herbicides have very short windows in which they can be applied.  The popular broadleaf weed herbicides 2,4-D and MCPA are efficient and economical, but can only be applied for a short period of time between tillering and prior to jointing in the early spring.  Wheat growth stages and herbicide timing restriction are outlined in Figure 1 above.

Nitrogen Application Timing for Weak Wheat Stands

Source: Ed Lentz, OSU Extension

Late-planted wheat fields had little opportunity for growth before cold and wet conditions moved into the area last November. Fall tiller production was limited because of early cold weather soon after planting. In addition, some wheat stands have been damaged this winter from lack of snow cover, standing water, saturated soils, ice sheets, and days of very cold temperatures.

In these situations, producers have asked whether they should apply nitrogen earlier to increase the number of spring tillers. Keep in mind, it is fall tillers that provide most of the yield in a wheat field. Heads developing from spring tillers generally are much smaller than heads from fall tillers.

In northern climates, the vegetative period of growth is much shorter than the other wheat regions of the country; thus, plants have a much shorter time to recover from winter damage. From my experience, producers will have limited success in improving yields of poor stands and stands with reduced-growth by applying nitrogen earlier. A producer may get a few more spring heads, but not enough to significantly change the yield situation. The earlier application will also significantly increase the risk of nitrogen loss. In fact, a producer may need to readjust their yield potential for these fields and reduce their total nitrogen rate accordingly.

Wheat does not need large amounts of nitrogen until jointing (Feekes GS 6), generally the latter part of April. Soil organic matter and/or nitrogen applied at planting generally provide sufficient nitrogen for early spring growth. Ohio research has shown no yield advantage for nitrogen applied before jointing. The longer the time between nitrogen application and jointing, the greater the risk for nitrogen loss. Nitrogen source will also affect the potential for loss. Urea-ammonium nitrate (28%) has the greatest potential for loss, ammonium sulfate the least, and urea would be somewhere between the two other sources.

Ohio research has also shown that yield losses may occur from nitrogen applied prior to green-up regardless of the nitrogen source. The level of loss depends on the year (losses would be smaller if the ground is not frozen or snow/ice covered). This same research did not observe a yield increase from applications made prior to green-up any year compared to green-up or Feekes GS 6 applications.  Keep in mind that green-up is a descriptive term and not a definable growth stage. My definition of green-up is when the new growth of spring has covered the dead tissue from winter giving the field a solid green color – thus, growing plants.

There is a legitimate concern that wet weather may prevent application of nitrogen at early stem elongation. Ohio research has shown a yield decrease may occur when nitrogen application is delayed until Feekes Growth Stage 9 (flag leaf fully emerged). Thus a practical compromise is to topdress nitrogen any time fields are suitable for application after initial green-up to Feekes GS 6. There is still a potential for loss even at green-up applications. To lessen this risk a producer may want to use a nitrogen source that has a lower potential for loss such as urea or ammonium sulfate. ESN (polymer-coated urea) would be another option but it needs to be blended with urea or ammonium sulfate to insure enough nitrogen will be available for the crop between Feekes GS 6 – 9. The source of nitrogen becomes less important as the application date approaches Feekes GS 6 (jointing). The percentage of urea and/or ammonium sulfate would need to be increased with ESN for application times closer to Feekes GS 6. A producer may want to consider the use of a urease inhibitor with urea if conditions are favorable for volatilization losses: warming temperatures, drying winds and no rain in the forecast for 48 hours.

A split application of nitrogen may also be used to spread the risk of nitrogen loss and to improve nitrogen efficiency; however, Ohio State University research has not shown a yield increase from this practice compared to a single application after green-up. In a split system, the first application should be applied no sooner than green-up. A smaller rate should be applied with the first application since little is needed by the crop at that time and the larger rate applied closer to Feekes GS 6.

In summary, some wheat fields look rough coming out of the winter. Applying nitrogen earlier may slightly increase the number of spring heads but probably not enough for a significant yield increase. The earlier application will increase the potential for nitrogen loss. University recommendation would be to topdress nitrogen when fields are suitable for application after initial green-up to early stem elongation.

American Society of Agronomy Webinar Series on Fusarium Head Blight

A national group of plant pathologists, including Pierce Paul from The Ohio State University, will be presenting a two-part webinar series to help U.S. wheat producers management Fusarium head blight (FHB), also known as head scab or scab. FHB affect wheat, barley and other small grain crops, reducing yield and contaminating grain with mycotoxins such as deoxynivalenol, AKA vomitoxin.

As part of this American Society of Agronomy series, Paul, Carl Bradley, plant pathologist at the University of Kentucky, and Christina Cowger, plant pathologist with the U.S. Department of Agriculture’s Agriculture Research Service, will present and discuss up-to-date research findings on cultural practices, variety resistance, and fungicides for effective management FHB and vomitoxin. The USDA-ARS U.S. Wheat and Barley Scab Initiative, which is sponsoring these webinars, funded much of the research the scientists will be presenting.

The webinars are at 11 a.m. CST on Monday Feb. 11 and Monday Feb. 18. Register for free at https://tinyurl.com/ycmvel4p.

Farm Science Review Agronomy College is September 11th

by: Harold Watters, OSU Extension

The FSR Agronomy College is held in partnership between the Ohio AgriBusiness Association & OSU Extension. The event is designed to educate agronomists, Certified Crop Advisers, custom applicators and farmers on current agronomy issues. The full-day event features time with OSU Extension staff in the field in the agronomy plots on the east side of the Farm Science Review grounds. Breakout sessions will feature topics including a weed management update, weed and crop screen, variable rate soybean seeding, an update to the Tri-State Fertilizer Recommendations, the new Ohio Phosphorus Index, and some how we will squeeze in even more. CCA and pesticide application credits available to those attending.

Date: September 11, 2018

Location: Farm Science Review – Molly Caren Agricultural Center, London, OH

Time: Check-in begins at 8:30 a.m.; sessions begin at 9 a.m. and concludes at 4:00 p.m.

Cost: $120 Registration: Click here to register for the event. (or try this link:http://oaba.net/aws/OABA/pt/sd/calendar/67757/_PARENT/layout_details/false)

Contact: Janice Welsheimer at 614-326-7520 or by email: jwelsheimer@oaba.net

Or for additional information, Harold Watters, 937-604-2415 or by email: watters.35@osu.edu