Some basic points on using anhydrous ammonia for wheat production

As producers start thinking about anhydrous application for wheat this fall, there are a few basic points which they should keep in mind, especially regarding safety. Ammonia is a hazardous material and safety should be the highest priority of the operator.

Even distribution of previous crop residues is extremely important for no-till wheat. Nitrogen applied on the surface can get tied up, or immobilized, on crop residues and be unavailable to the currently growing crop for several months or longer. Where there are windrows of residue, the N immobilization potential is especially high for surface-applied materials. Also, where wheat is planted into fields with an uneven distribution of crop residue, the wheat may have poor stand establishment and root development in the areas of especially heavy residue.

* No-till wheat may require an extra 20 to 30 lbs of N per acre compared to conventional-till wheat. One reason for this is that no-till soils are generally cooler, and have lower N mineralization rates. Another reason is that organic matter levels tend to build up slowly in no-till soils, and this process uses and stores soil N. For example, every percent organic matter in the top 6-7 inches of soil contains about 1,000 pounds of N per acre. If the soil organic matter level were to increase by a full percentage point over 20 years, an extra 50 lbs N per year per acre would need to be invested just to build up the organic matter level. That's over and above the needs of the crop.

* Topdress N should be in the root zone by jointing. Producers should not wait too long to apply topdress N. Topdress applications should be applied early enough to have a good chance of moving down into the root zone by jointing. By waiting until the last minute, producers run the risk of being prevented by wet weather from applying the N in time. On the other extreme, late-applied topdress N may not receive any precipitation for a time after it is applied, and thus may not get into the root zone when the plant needs it most to maximize yield potential.

* Urea-containing N fertilizer products (such as dry urea or N solutions) should not be placed in direct seed contact as a starter fertilizer.

* On medium- and fine-textures soils with adequate internal drainage, applying N in a subsurface band is generally more efficient and consistent than surface-applied N in no-till. A subsurface band minimizes or eliminates the potential for immobilization, places N in the active root zone where it is needed, and would eliminate any potential for volatilization losses if it exists.

* For surface applications of N, applying it in a dribble band is generally more efficient and consistent that broadcast N, but not as consistent as subsurface applications.

* Although broadcast surface applications of N are often somewhat less efficient and consistent overall than subsurface band applications, there are can be many reasons that broadcast applications better fit many producers operations;

-- Can cover more acres per day

-- Does not require specialized equipment

-- Does not require extra horsepower or fuel use

-- Allowing producers to tank mix with herbicides in a single application

While topdress N applications to wheat may sometimes result in some leaf burn (especially late applications in early spring), it is generally cosmetic only and has not resulted in noticeable yield loss in Kansas trials.

* On well drained, medium- and fine-textured soils, there is generally no agronomic advantage to making multiple split applications of N. For no-till wheat, however, there may be an advantage to applying at least 20 to 30 lbs of N preplant or at planting time in order to supply adequate N for fall growth.

* On poorly drained or claypan soils, topdress applications of N are preferred. Fall applications of N are subject to denitrification losses on these soils.

 

Correlation of soil test nitrate level, N rates, and wheat yields

Soil testing for nitrate-N in the fall for making nitrogen (N) recommendations on winter wheat is a valuable practice, particularly when using 24-inch profile sampling. Unfortunately, few farmers utilize this tool, and its value has been questioned in some areas due to the potential for overwinter N loss. However, with the exception of sands, N losses over winter in Kansas are normally quite low due to our low rainfall in December, January, and February.

 

Foliar nitrogen fertilizer products for wheat

Various foliar nitrogen (N) fertilizer products are sometimes promoted as an option for spring fertilization of wheat. These products range in analysis and can include straight nitrogen products or mixtures of N plus other macro and micro nutrients. The straight nitrogen products will typically have an analysis similar to traditional liquid N fertilizers, such as 25 to 30 percent N.

Topdressing wheat and weed control to prevent kochia emergence radio program

 

Nitrogen topdressing on wheat

Now is a good time to start planning for topdressing nitrogen (N) of the winter wheat crop. With the temperature swings and seemingly warm winter during the end of January and the first of February, there are some key elements that need to be considered when deciding on the exact program you plan to use. These include: timing, nitrogen source, application method and nitrogen rate.

Ideally, the N in topdress applications will be moved into the root zone with precipitation well before jointing begins in order to be most efficiently utilized by wheat. With a great deal of the wheat not having a chance to tiller last fall, having adequate N available to support spring tillering when it breaks dormancy will be important. Some combination of fall preplant or at-seeding N, and/or early topdressed N, is also normally needed to supply adequate N to support head differentiation. This is the stage when head size is being determined and can begin about two weeks before jointing. The following will discuss some of the issues to consider when making topdressing decisions.

 

Nitrogen management considerations for wheat

Tillage systems affect nitrogen (N) management for wheat in many ways. Nitrogen rates, application methods, and timing can all be affected by tillage considerations.

 

Late topdressing of wheat

The heavy dose of precipitation in Kansas during late December and January may mean that soils will stay wet through at least late winter or early spring. Producers who were planning to topdress nitrogen (N) on their wheat during this time period may have to wait longer than they'd like for soils to dry out enough to make the application. This could mean that the N will go on later than usual. How late can producers topdress their wheat and still get a yield benefit?