Earlier this spring in southeast Nebraska, much of the corn looked very anemic. Much of this was due to all the rain we received this spring and lack of sunshine. The corn roots had not reached the nitrogen in the soil either to help with the problem. With drier conditions, warmer temperatures and sunshine received throughout June, most of the corn has improved greatly. With the recent rain last weekend and the cooler temperatures this week, the corn generally looks better, but some of the corn is still yellow and may respond to added nitrogen.
What about fields or areas in fields that are staying yellow? This week in traveling around southeast Nebraska, I still see some fields with significant areas of yellow corn present. The question is, “Is there still nitrogen available in the soil for the corn plant to utilize or has it been lost to the environment?” Most of southeast Nebraska has had major thunderstorms (2-3” of rain multiple times), this spring and if liquid nitrogen had been applied on the surface, much of this may have washed away. If nitrogen was applied into the soil, it may have been leached down below the current root zone. Under the saturated (anaerobic) soil conditions, nitrogen may have been lost to the atmosphere as a gas in a process called denitrification. All of these factors may be contributing to the yellow corn.
With current technology, some producers are using sensors either on a ground rig or with an unmanned aerial vehicle to evaluate nitrogen status of corn and applying nitrogen accordingly to meet the crop needs. Nebraska Extension has been conducting research using sensors on a high clearance ground rig to improve nitrogen management, especially in nitrogen management areas where ground water is threatened by high nitrogen levels. A base amount of nitrogen is applied before planting and nitrogen is then side-dressed with this rig to meet the crop needs. To learn more about “Project Sense” this research project and tool for nitrogen management go to: http://cropwatch.unl.edu/projectsense .
In previous years I have conducted some small plot on-farm research in Nemaha County. Nitrogen was surface applied in a dry form as urea (46-0-0) at tassling at the rates of 0, 50, 75 and 100 lbs. of nitrogen (N) per acre. This method simulated nitrogen being top-dressed with a high clearance ground applicator or through aerial application. Results of this experiment showed a significant increase in yield when N was applied mid-season to the nitrogen deficient corn top-dressed treatments respectively. For more information about these On-Farm Research Experiments go to: http://cropwatch.unl.edu/farmresearch/resultshome . Results for 2013 can be accessed in the report under the title Mid-season N, for 2014 results are listed under the title In-season Additional N on Deficient Corn and for 2015 results can be found under the title Nitrogen Sidedressed to Simulate Aerial N Application . These applications were made at the R1 or R2 growth stage of the corn, so nitrogen application to yellow corn may be feasible. If nitrogen is surface applied as urea, the key is getting sufficient rainfall following nitrogen application so the crop can use it.
If corn is nitrogen deficient, the application of 75-100 pounds of nitrogen per acre should pay for itself if you can get it on. The past few years, farmers in northwest Missouri, northeast Kansas and southeast Nebraska have applied nitrogen with airplanes in fields that were N deficient. High clearance ground rigs may also be used for nitrogen application.
If you have questions about this subject feel free to contact me at Nebraska Extension (402) 274-4755.