The wheat crop has stalled. Fall forage has been subpar on early sown wheat, and late-sown wheat has taken weeks to even emerge. I attribute most of this to short stretches of drought for some and cold soils for most.
In reviewing some data from Mesonet, soil temperatures have been much cooler since mid-October than the 2004-2018 average.
Some days for certain north central Oklahoma locations show as much as a 10 to 18 degree difference. Once soil temperatures drop below 50, growth rate is reduced.
Nitrogen (N) is a mobile nutrient and can be lost or become unavailable to plants. Due to these risks, the best management practice is to split apply N. These split applications typically occur at planting and prior to spring green up for a winter crop like wheat. Different production systems will require more or less nitrogen up front than others.
In a dual-purpose or graze-out wheat system, more N is needed early compared to a grain-only system. A grain-only system needs about 2 pounds of N per bushel of seed produced, or 80 pounds of N for a 40-bushel grain yield. Producing wheat forage is greatly influenced by available N to the wheat crop, so more N is needed in a dual-purpose or graze-out system to produce adequate forage. For every 60 pounds of N, one ton of wheat forage is expected to be produced. So in a dual-purpose system 60-70 pounds of N will be needed at planting compared to 30-40 pounds of N for a grain-only system.
The second application of N is typically applied late fall to early spring.
Since wheat is in the ground for almost nine months, it is almost impossible to determine the total N needs at the time of planting.
Topdressing N 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 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 can help estimate N demands throughout the year. 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) to custom built applicators on UAV’s or tractors. The strips can be used to visually determine if there is enough N or not for the rest of the field. If the strip cannot be seen, then there is no need to apply N at that time. If the strip can easily be seen, then more N is needed.
Due to low commodity prices, managing N economically is very important. In addition to using N-rich strips, all Oklahoma Cooperative Extension Service offices have access to a GreenSeeker crop sensor. The hand-held sensors estimate the biomass and greenness of the crop both in and out of the N-rich strip. Using the data from the sensor and an online calculator, yield estimates can be computed. This tool can help producers determine the yield potential of their crop with and without added N to make economic decisions on if or how much N needs to be topdressed. From past on-farm data, utilizing N-Rich strips with a hand-held sensor averaged a net profit of $10 per acre or more.
Contact your local extension office for more information.