It continues to rain. Much of Northwest Oklahoma is unaccustomed to timely moisture through the winter months as producers have been faced with difficult growing seasons in the past few years. The strong start to 2020 beckons a look at the current wheat crop and what can be invested as it nears harvest.
With the exception of Cimarron County, every county in Oklahoma has a one-day average 4-inch fractional water index of 0.7 or greater, according to Oklahoma Mesonet. This scale can be read as 0 being completely dry and 1 being completely saturated. Therefore, there is ample moisture available currently.
Looking at another scale, the majority of the state has at least 0.5 inches of plant available water in the top 4 inches of soil, meaning that growing conditions are good. This bodes well for Oklahoma producers and U.S. Department of Agriculture’s National Agricultural Statistics Service tends to agree. In the December crop progress report, Oklahoma wheat was rated at 45% good to excellent.
What should a producer do with this good news? The wheat market has been improving in recent weeks on concerns over Russian wheat exports and increased U.S. exports. This price increase helps producers only if they can raise extra bushels. In order to do that, fertility has to be adequate.
If producers are interested in pushing yields this year, they likely will need to make additional nitrogen applications. Excess rainfall can push nitrogen below the root zone and leave plants with a deficiency.
Topdress nitrogen applications are a good way to combat this problem and to make up for fertility goals not achieved earlier in the season.
It is not enough to just spread nitrogen in the hopes of it entering the soil profile. Nitrogen is safest from volatility (loss) when incorporated into the ground. That can be difficult in standing wheat, so producers tend to time applications before a rain to attempt to get nitrogen incorporated into the soil.
Applying 65 pounds of urea on a 60 degree day, with a soil pH of 5 and wind speed of 10 mph, a producer can expect to lose 30% of their applied urea without an incorporating rain event. This is 19 pounds of urea or approximately 9 pounds of actual nitrogen. Wheat requires 2 pounds of nitrogen per bushel, so a producer is losing a potential 4.5 bushels of production or ~$20 per acre of revenue.
Another popular topdress option available to producers is liquid UAN or 28-0-0. While a portion of this fertilizer is nitrate, which will not volatilize, it is not immune from losses. There also is the potential for leaf burn when applied broadcast to wheat foliage in warmer temperatures. Without immediate incorporating rainfall, it is safer to incorporate this fertilizer into the soil upon application.
Perhaps the least utilized form of nitrogen for topdress application is anhydrous ammonia or 82-0-0. This fertilizer source must be incorporated by specialty low disturbance applicators to minimize plant loss in growing wheat. With a more expensive application method, why would a producer choose to use this nitrogen source?
It all comes down to the cost of the fertilizer. As producers try to minimize costs they must get creative with their production practices. When computing nitrogen costs per pound of actual nitrogen, anhydrous ammonia is the cheapest source.
Using current market prices, anhydrous ammonia costs 24 cents, urea costs 36 cents and UAN costs 39 cents per pound of N. There is 15 cent per pound of N difference between anhydrous ammonia and UAN. When used as a single source for a yield goal of 40 bushels, that is a difference of $12 per acre or 3.7 bushels of revenue. This does not account for the added benefit of soil incorporation to reduce loss; nitrogen losses drive up the cost of urea and UAN applications.
If you would like more information on budgeting, topdress fertilizer application or nitrogen application costs please contact your local county extension agent.