It’s November 1st as I write this. With much of harvest done, the next task for some may be fall herbicide applications and/or fall anhydrous application.
Fall Anhydrous: With nutrient management, we’re hearing more about the 4R’s. 1-Right Time is after Nov. 1st in our area NRDs. Extra important, consider soil temperature. Soil microbial activity and the conversion rate of ammonium to nitrate is very low when the soil temperature is less than 50oF. Thus, apply fertilizer-N (and manure) when the soil temperature at the 4” soil depth is below 50°F and trending cooler. You can view soil temps at: https://cropwatch.unl.edu/soiltemperature. 2-Right Source in the fall is anhydrous ammonia as it will bind to soil particles. Leaching risk is reduced in a dry fall and when applied at soil temperatures below 50°F. 3-Right Rate for each field is based on soil samples and various nitrogen credits. Can also consider splitting the application with part this fall and the remainder next season. 4-Right Place is making sure the anhydrous is deep enough. It’s also ensuring there’s a good seal, which will be something to watch in this dry fall.
Fall Herbicide is one management tool to control winter annual weeds and marestail (horseweed); it may not be necessary for every field. It’s important to scout fields for current weed pressure. Also consider targeting fields that have a history of winter annual weeds or marestail. Nebraska research shows up to 95% of marestail germinates in the fall, so fall application can aid management. Some winter annual weeds also serve as hosts for pathogens like soybean cyst nematode (SCN): purple deadnettle (strong host), henbit (strong host), field pennycress (moderate host), shepherd’s-purse (weak host), small-flowered bittercress (weak host), and common chickweed (weak host). SCN can reproduce in the field on henbit and purple deadnettle.
If you have a 2020 Guide for Weed, Disease and Insect Management, page 81 provides fall burndown corn herbicide options and page 127 provides soybean ones (I also show these at https://jenreesources.com/). Most products contain 2,4-D and/or dicamba. Tank-mixing a residual herbicide with a burndown product will improve marestail control because the residual activity will control marestail emerging after herbicide application. Be sure to check labels for any grazing restrictions if livestock will graze cornstalks after a fall herbicide application (You can find these on pages 200-204 of the 2020 Guide). If the label doesn’t specify and you want to be on the safe side, a rule of thumb is to use the pre-harvest interval for the amount of time to wait before grazing stalks.
Regarding temperatures, in a CropWatch article Dr. Amit Jhala and I shared the ideal temperature for applying most post-emergence herbicides is between 65°F and 85°F. Herbicides can be applied at 40°F to 60°F, but weeds may be killed slowly. When the temperature is below 40°F for an extended time after burndown, weed control will most likely be reduced, specifically for a systemic burndown herbicide such as glyphosate. Additionally, weed control may be reduced under cloudy conditions following an initial temperature drop below 40°F. With late-fall herbicide applications be sure to add labeled adjuvants to improve herbicide efficacy.
Actively growing weeds are key to achieving good control, regardless of herbicide used. Frosts of less than 25°F usually cause leaf damage to annual plants, making them poor targets for herbicide applications; however, winter annual weeds may tolerate a frost up to 20°F and continue growing when conditions improve, with little tissue damage. After weeds experience frost, active growth may not begin again for a few days. Growers should wait until new leaf tissue is produced, scout the field, and then consider applying herbicide. Generally, this would be when nighttime temperatures are 35°F or greater and daytime temperatures are at least 50°F for two consecutive days. Additionally, sunshine is needed for plants to recover.
York County Corn Grower Plot Results and Banquet: The results of the York County Corn Growers plot can be found at: https://jenreesources.com/2019/11/03/2019-york-county-corn-grower-plot-results/. Special thanks to Ron and Brad Makovicka for their dedication and work in hosting! Also appreciate all the seed companies who participate! The York County Corn Grower’s Banquet will be held Tuesday, November 26 at Chances ‘R in York with social at 6:30 p.m. and dinner at 7:00 p.m. Tickets are $10 and may be purchased from any York Co. Corn Grower director or at the York Co. Extension Office.
Fall Nitrogen Application: With November here, a reminder to check soil temperatures before applying anhydrous ammonia to crop fields. Soil microbial activity and the rate of conversion of ammonium to nitrate is very low when the soil temperature is less than 50oF. Thus, apply fertilizer-N (and manure) when the soil temperature at the 4” soil depth is below 50°F and trending cooler. Daily and weekly soil temperatures (taken 4” below the surface of bare soil) can be found at: https://cropwatch.unl.edu/soiltemperature.
Extension Soil Fertility and Nutrient Management Specialists Javed Iqbal, Charlie Wortmann, Bijesh Maharjan, and Laila Puntel shared additional considerations for fall Nitrogen application in this week’s CropWatch: Apply anhydrous ammonia rather than other N fertilizers; Limit fall application of N to silt loam, silty clay loam, and finer textured soils; Use nitrification inhibitors to slow the conversion of ammonium to nitrate, especially on sand-dominant soils; Avoid fall application on wet soils; and Consider applying a lower base rate of nitrogen in the fall and plan on applying the rest at planting, or as a side-dress application.
On-Farm Research Protocols are available for anyone interested in fall vs. spring nitrogen management studies, inhibitor studies, or other potential on-farm research studies by contacting your local Extension educator. For growers within the UBBNRD interested in on-farm research studies that have a water quality focus, you may be eligible for additional support through the UBBNRD. In some instances it may cover district staff and equipment use; in others, it may cover a portion of the costs of lab analysis of soil, plant tissue, or water samples. If you’re a grower interested in this type of study, please contact the UBBNRD or your local Extension Educator to talk through your study idea and for additional information.
Farm Bill Meetings: Joint Nebraska Extension and Nebraska Farm Service Agency (FSA) producer education meetings are scheduled at 28 locations across the state from late November to mid-December in advance of the coming ARC/PLC enrollment deadlines in early 2020. The meetings are free and open to the public. Advance registration is encouraged for planning purposes for materials and facilities. Attendees can register for any of the meetings conveniently on the web at farmbill.unl.edu or by calling or visiting their county FSA or Extension office. The educational programs will feature information and insights from FSA specialists and Extension experts, as well as other relevant information from local agencies.
Nearest locations for this area of the State include: Nov. 25. Community Center, Red Cloud (1-4 p.m.); Dec. 3 ENREC near Mead (9-Noon); Dec. 4 Ag Park in Columbus (9-Noon); Dec. 5 College Park in Grand Island (1-4 p.m.); Dec. 5. Opera House, Bruning (1:30-4:30 p.m.); Dec. 6 Fairgrounds Cornerstone Building York (9-Noon); Dec. 16. Extension Office Lincoln (9-Noon); Dec. 17 Fairgrounds 4-H Bldg. Beatrice (9-Noon); Dec. 17 Fairgrounds in Kearney (1-4 p.m.).
Through the years I’ve been blessed to meet many individuals including farmers/ag industry professionals who served (or continue to serve) our Country in the military. I’ve observed how service has influenced perspective on life’s difficulties for many individuals. And, I’ve observed how impacts of service have resulted in additional difficulties in life after service for some. There shouldn’t be shame regarding the struggle or in seeking help. While it can be scary, healing can come in the midst of honesty and vulnerability. Tonight I watched a special TV interview with four highly decorated individuals of the Iraq/Afghanistan wars-a couple of whom I’ve read their books. It was interesting hearing their perspectives on combat then coming home, on being in the military and then getting out, and much more. They ultimately shared how difficult it is after war and after service to step into civilian life and how important their military connections were in keeping them going. They also shared how important it was to find a sense of purpose in serving others and living life well in honor of those with whom they served who never made it home. Most likely all of us can think of a family member or friend who has served. Those individuals may have stories and/or wounds without words. Let’s be sure to show our gratitude to them for our freedom in America. Thank you to all our Veterans and all those in our Armed Forces for your service! Thank you also to their families!
Fall Applied Anhydrous Ammonia: When I began my Extension career, it was a different perspective for me to experience fall applications of nitrogen. My perspective from our farm was in-season nitrogen applications. Since then, there’s been several research based studies regarding the benefits of in-season nitrogen application. I appreciate there’s different reasons for the ways farmers approach the decisions within your farming operation. I’ve also observed more farmers of various operation sizes moving to more in-season applications. The reasons they’ve shared with me include: wanting to be more efficient with nitrogen application when the plant needs it, worried about any loss in off-season and wanting better water quality for kids/grandkids, research shows hybrids need nitrogen later in season, wanting to find a way to make it work before any potential regulation, and wondering if they can get by with less nitrogen with better timing in season. We also know today’s farmers in general have become increasingly efficient in both nitrogen and water use. There’s an interesting article in this week’s UNL CropWatch (http://cropwatch.unl.edu) where a multi-disciplinary team of authors share on nitrogen application in the fall having enhanced risk due to potential loss. This is due to data on the increase in extreme precipitation events over time that can lead to increased nitrogen loss through leaching and/or denitrification. We also know that there are years, like last winter, where areas I served didn’t even receive 2” of precip from fall through early May. So every year is different. Because we can’t predict the weather, the authors suggest, “Consider a more robust and less risky N management method that includes: applying a small percentage of N near planting time; follow with sidedress N applied as late as is possible given your equipment capabilities or several fertigation applications that are timed with crop uptake needs; and ensure the final application of N is done before the R3 growth stage.” They also suggest the following if you plan to apply N in the fall, “Avoid fall N application for soils of hydrologic Group A (sand, loamy sand, sandy loam) and Group B (loam, silt loam, silt); Avoid fall application of fertilizers containing urea or nitrate; Apply only when soil temperature is consistently below 50°F to slow nitrification (Last week temperatures fluctuated above and below 50°F at the 4-inch depth.); Use an inhibitor with known efficacy when applying N; and Hope for dry cold weather!”. The following is a really good resource if you’re interested in different University studies regarding various nitrogen inhibitors: https://www.ag.ndsu.edu/publications/crops/nitrogen-extenders-and-additives-for-field-crops. It’s too long to share here. A general summary of studies involving the inhibitor N-Serve used with anhydrous ammonia applications shows that it consistently resulted in increased ammonium nitrate the following spring (thus it worked well as a nitrification inhibitor). Yield increases were inconsistent throughout studies and years due to precipitation differences amongst the years. That resource also discusses research regarding other nitrification inhibitors in addition to urease inhibitors and slow-release N products, so it may be a helpful resource. We’ve also had farmers conduct on-farm research studies in the past looking at the application of inhibitors in anhydrous vs. none. They also haven’t consistently shown a yield increase (and we failed to always take soil samples to document any differences in ammonium nitrate the following spring). But if you’re interested in trying a study this coming year looking at nitrogen timing or use of inhibitor, please contact me or your local Extension Educator and we’d be happy to work with you!