Extension

Wheat and Corn Nitrogen Management

Josh Bushong, Area Extension Agronomist

 

Low wheat prices and continued drought should force farmers to be extra thoughtful on managing fertility plans this fall. Sowing winter crops has started, and I’ve received a few questions about how much nitrogen should be applied and how much can be applied in-furrow. Forage and grain yield goals are going to be heavily hinged on timely moisture, since most of the region is in “D1 Moderate Drought” according to the U.S. Drought Monitor.

Nitrogen (N) is a mobile nutrient and can be lost or become unavailable to plants. Source or type of N fertilizer used can also have a big impact. Different production systems will require more or less nitrogen up front than others.

In a dual-purpose or grazeout wheat system, more N is needed early compared to a grain only system to produce more forage. A grain only system needs about 2 lb N per bu of seed produced, or 80 lb N for a 40 bu grain yield. It takes about 60 lb of N to produce one ton of wheat forage. So in a dual-purpose system 60-70 lb of N will be needed at planting compared to 30-40 lb of N for a grain only system. The second application of N is typically applied late fall to early spring.

Many grain drills and especially air seeders can apply fertilizer in-furrow directly with the seed wheat. Farmers with acidic, low pH, soils often use this practice to apply phosphorus to mitigate some availability issues and aluminum toxicity. To prevent germination issues, OSU recommends to keep the salt load (N and potassium) to no more than 30 pounds when sown on 6-8 inch ow spacing in medium to fine textured soils and 21 pounds on sandy or dry soils. Applying 167 pounds of 18-46-0 would yield 30 pounds of N.

It is not recommended to use or blend in N fertilizers and place it directly with the seed as it could cause more seed and seedling injury. When urea (46-0-0) is placed in-furrow it initially converts to ammonia. Ammonia can be toxic to plant roots and reduce seed germination. The risk of injury is higher in drier soils, in higher pH soils, and when applied at higher rates. Field research from KSU has shown stand reductions of 32% when 30 pounds of N from urea was applied in-furrow. This resulted in a 14% grain yield reduction.

For grain only producers, the old rule of thumb of 2 lb N per bushel is a good starting place but that might be on overestimation. When looking at more than 15 years of field trial data from the OSU North Central Research Station near Lahoma, the optimum pounds of N per bushel ranged from 0 to 3.2. The average pounds of N per bushel to reach an economic optimum N rate was 1.6, however if 2 pounds per bushel was applied the grain yield would have been maximized 13 out of those 15 years.

Split application is often a best management practice in canola as well. The canola crop needs enough N to produce a healthy crop to better withstand the winter. Too much N in the fall or at planting can result in excessively large plants going into winter. Excessive N and prolonged warm growing conditions can lead to winter survival issues if the plants growing point starts to vertically elongate. Canola needs about 2.5 lb N per bushel of seed yield, or 100 lb N for a 40 bu yield.

It is almost impossible to determine the total N needs at the time of planting to maximize grain yields. Topdressing N on wheat and canola is a good management practice because it decreases the risk of N losses as well as benefiting from influencing late season N recommendations based on the potential yield of the crop. Topdress application rates can be impacted by current expectations of the crop and weather forecasts. Basically, estimating the yield potential becomes more accurate as the season progresses.

Utilizing tools at hand can dramatically influence N recommendations. Applying N-Rich strips in early fall, especially in dry years like this, can help estimate N demands throughout the year for both dual-purpose and grain-only systems. This management tool can assist in determining N deficiencies or sufficiency.

The N-rich strips can be as simple as hand spreading a few cups of urea (46-0-0) or more technical with using custom built applicators on UTV’s or tractors. The strips can simply be used to visually determine if there is enough N or not. If the strip cannot be seen, then there is a low likelihood of getting a response to additional N. If the strip can easily be seen, then more N is likely needed.

Contact your  local OSU County Extension Office for more information.

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Understanding Woody Plant Encroachment in Oklahoma

Dana Zook, NW OK Area Livestock Specialist

 

Hello! Happy August. It’s been a wild summer with serious heat paired with some delightfully cool days. This month I thought I would tell you about an excellent learning opportunity I have been involved in this summer. Sometimes, Extension Educators sit in an office and answer a consistent stream of questions over email and phone. But there are also times that we get take time to learn and build our knowledge base so that we can better serve the people within our counties. I recently got to bust out of my office and do some learning this summer and I hope you enjoy this insight into that opportunity.

This Spring, I was selected for the Climate Hub Partnership Project. Educators from across Texas, Oklahoma, Kansas and Nebraska were selected to learn more about the impacts of Drought, Wildfire, and Woody Plant Encroachment on Livestock Production in the Great Plains. As a member of this group, I have been able to learn from leading researchers and extension specialists in rangeland and fire ecology from OSU, Texas A&M and the University of Nebraska. Our year-long program was initiated with a multi-day field tour in June that illustrated rangeland management using fire, livestock, and a combination of the two. The insights from the researchers and my fellow cohort members created an exceptional learning experience.

Some of the most interesting and relevant information I have learned this summer is about fire and how the reduced frequency of burning has allowed woody plant encroachment to occur in the Great Plains. In the most basic terms, “woody plant encroachment” refers to unimpeded growth and expansion of both native and introduced woody plants across rangeland. The Eastern redcedar (Juniperus virginiana) is one of the biggest culprits of this expansion, but other species have also played a role. Eastern redcedar specifically was once thought to be a good option for windbreaks and woodlots, so these trees were planted across the Great Plains when people first settled this area. This initiated the seed bank for many woody species and with reduced fire, this species was off to the races.

In my location in Northwest Oklahoma, the topic of tree encroachment is never far from my mind and that of local livestock producers. Tree and other woody plant encroachment occurs quickly and many don’t realize the impact until the problem seems unsolvable. In the past, woody plants were controlled through consistent fire. Fire return interval or fire frequency is a term that is used to estimate how often fire returns to a landscape. When grasslands burn more often (lower fire return interval, higher frequency), woody plants are naturally controlled. There are many estimates of fire frequency in the U.S. but Guyette and others in Oak Fire Science (2012) estimate the historical fire return interval for a majority of Oklahoma to be approximately 4-6 years. Fire frequency has decreased in many areas of Oklahoma which has led to a significant reduction in productivity of our rangeland. In the coming months, we will dig into this topic and look at how range productivity is reduced at the “cow-level.” In the meantime, if this has piqued your interest, check out a recent Extension Experience Podcast Re-run of a discussion about cedar trees. You can find us on Apple Podcasts, Spotify, or Spotlight.

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Asian Longhorned Tick (Haemaphysalis longicornis)

Barry Whitworth, DVM, Senior Extension Specialist/BQA State Coordinator, Department of Animal & Food Sciences, Ferguson College of Agriculture

 

Dr. Rod Hall, Oklahoma State Veterinarian, recently announced the finding of the Asian Longhorned Tick (ALT) (Haemaphysalis longicornis) in Mayes County in northeastern Oklahoma. Since the tick’s initial discovery, the ALT continues to move across the United States. Prior to this announcement, the tick had been found in 20 states including Arkansas, Connecticut, Delaware, Georgia, Illinois, Indiana, Kentucky, Maryland, Massachusetts, Missouri, New Jersey, New York, North Carolina, Ohio, Pennsylvania, Rhode Island, South Carolina, Tennessee, Virginia, West Virginia, and Washinton D.C. The tick was originally found in New Jersy in 2017; however, additional research determined that the tick has been in the United States since 2010. The ALT is native to East Asia found in China, Japan, Republic of Korea, and southeast Russia. The tick has been introduced into Australia, New Zealand, and several Pacific Islands as well as the U.S.

 

The ALT is found on people, pets, livestock, and wild animals. The tick resides in areas high in humidity such as tall grass and wooded areas. The female tick can reproduce without having to mate with a male tick. These females are capable of laying very large numbers of eggs which can result in large populations of ticks in pastures or on animals in a short period of time. Infestation is stressful to the animal and may compromise growth and production. In severe infestations, extreme blood loss may result in death.

 

As this tick continues its westward migration, the tick may cause production issues in cattle as well as a cattle disease called Theileriosis. Theileria orientalis genotype Ikeda is a hemoprotozoan. A hemoprotozoan affects red blood cells and leukocytes. T. orientalis genotype Ikeda has been associated with severe bovine disease in other countries. A recent study in the U.S. demonstrated that a U.S. population of the invasive ALT is capable of transmitting T. orientalis Ikeda genotype. The particular strain of T. oreintalis genotype Ikeda used in the study was isolated from a beef herd outbreak of Theileriosis in Virginia in 2017. Although not conclusive, this study provides evidence that the outbreak of Theileriosis in the cattle in Virginia may have been caused by Asian Longhorned ticks infected with T. oreintalis genotype Ikeda.

 

Controlling ticks usually requires a combination of control methods. Livestock producers should consult with their veterinarian for the best insecticide for ALT. In addition to insecticides, pastures need to be managed to reduce tick numbers. This requires producers to rotate pastures to avoid wooded and brushy areas when tick numbers are high. In addition to pasture rotation, practices such as long-term control burning can significantly lower tick numbers. Also, animals on a good plane of nutrition are better suited to fighting off diseases and parasites. Producers should follow biosecurity protocols and isolate and exam all newly purchased cattle before allowing those animals to enter the herd. These animals should be treated for external and internal parasites.

 

If livestock producers suspect that an animals may be infested with Asian Longhorned Tick, they should contact their veterinarian and/or their Oklahoma State University Cooperative County Extension Agriculture Educator. Additionally, specimens can be collected in sealed containers such as a Ziploc bag or small water bottle; a glass vial containing 70% ethanol is the best method. If submitting samples in any container other than a glass vial, the specimens should be submitted dry/without preservative solution. Samples should be submitted for identification to the Oklahoma Animal Disease Diagnostic Laboratory using the General Submittal From. In the History section, indicate “Asian Longhorned Tick ID”, and be sure to include: the address of where the tick was found, the date collected, and the host the tick was collected from (i.e. cattle, dog, etc.). Samples can be sent to:

 

Oklahoma Animal Disease Diagnostic Laboratory

1950 W. Farm Road

Stillwater, OK 74078

 

Additional information about the ALT can be found at the Asian longhorned tick, Haemaphysalis longicornis, in Oklahoma E-Pest Alert.

 

References

Dinkel, K. D., Herndon, D. R., Noh, S. M., Lahmers, K. K., Todd, S. M., Ueti, M. W., Scoles, G. A., Mason, K. L., & Fry, L. M. (2021). A U.S. isolate of Theileria orientalis, Ikeda genotype, is transmitted to cattle by the invasive Asian longhorned tick, Haemaphysalis longicornis. Parasites & vectors, 14(1), 157.

 

Gleim ER, Conner LM, Berghaus RD, Levin ML, Zemtsova GE, Yabsley MJ. The phenology of ticks and the effects of long-term prescribed burning on tick population dynamics in southwestern Georgia and northwestern Florida. PLoS One. 2014;9(11):e112174. Published 2014 Nov 6.