Plan for wheat success
Proper nitrogen rates and timing returns more on your investment.
Increasingly, growers look to increase wheat production through more intensive management practices. From seeding practices to pest control, increased management frequently pays dividends in wheat production. Nitrogen fertilization in wheat is no exception, but you will need extra attention and planning to make the practice payoff. The proper rate, timing, source, and timing of nitrogen fertilizer will help you get the most efficient use of your nitrogen investment—and it will help manage variables such as tiller production and standability.
Rate and timing considerations
Like most crops, the nitrogen rate for wheat is best determined by a reasonable yield goal. Too often though, wheat nitrogen needs are underestimated. For every bushel of grain produced, wheat needs 1.75 pounds of nitrogen. That means for an 80-bushel-per-acre wheat yield, the crop needs 140 pounds of nitrogen. In a scenario where you can estimate a 20 pound nitrogen credit from past crops and organic matter, 120 pounds of nitrogen would still be required to reach that yield goal. To minimize lodging, reduce nitrogen losses, increase efficiency of nitrogen use and promote tillering, you need to determine how much to split up the application of that 120 pounds, and when we need to make the applications.
The primary reason some nitrogen is recommended in fall applications is tiller promotion. In most situations with phosphorous fertilizers such as DAP (18-46-0) or MESZ (12-40-0-10S-1Zn), the nitrogen applied with the phosphorous fertilizers is adequate for fall tillering—as long as you are getting at least 20 pounds of nitrogen per acre. Ideally, you want to see wheat produce one to two tillers per plant to supplement the main stem in the fall months, but even with proper nitrogen rates, this is not always possible due to variances in planting dates and the date which wheat enters dormancy. Because of this variability, you need to take stand and tiller counts in spring prior to green-up to determine optimal timing for top-dress applications. As a rule of thumb, at 70 tillers per square foot or fewer, an early spring application of 30 to 50 percent of the total spring nitrogen application should be made just prior to the wheat breaking dormancy. This induces tiller production. The remaining 50 to 70 percent of nitrogen is then applied at jointing. If tiller counts exceed 70 plants per square foot on average, the total sum of spring nitrogen can be applied at or near jointing.
Whether in a single application or in split applications, nitrogen applications delayed until jointing can provide several advantages. First, the nitrogen is applied closer to the time when the wheat plant has a higher demand for it. In turn nitrogen is not exposed as long to possible losses from denitrification and leaching. Second, delayed applications may reduce unwanted tillering. Excessive tillering can lead to “sucker” heads that may be less productive and divert nutrients from heads on primary and secondary tillers. Third, by delaying rapid stem elongation and reducing internode lengths, delayed nitrogen may reduce lodging risks often associated with high nitrogen rates in cereal crops.
Nitrogen source and placement considerations
Just as important as rate and timing is the nitrogen source and the placement of the fertilizer. Going forward, urea and UAN likely will be the most common sources of nitrogen fertilizer for top-dressing wheat. Both are effective nitrogen fertilizer sources, especially when coupled with the nitrogen stabilizer such as the products MFA’s director of agronomy Dr. Jason Weirich outlines on page 8. However, each one of them has a couple things to consider in terms of proper placement.
Stabilized urea is an excellent choice for top dress wheat applications in the spring. For applications prior to joining, there are few concerns about nitrogen loss for stabilized urea. However, late-spring applications after jointing may expose the crop to additional traffic damage from wide floater-type tires. To limit this damage narrow tire applicators are highly recommended for latespring applications.
While narrow-tired liquid applicators are more common for late-season applications of UAN, the leaf burn associated with it can affect yields. UAN is also more likely to tie up on surface residue. Use of streamer bars or streamer tips can reduce the leaf area exposed to burn as well as reduce the amount of tie-up by concentrating the UAN in bands.
Getting the most return from nitrogen applications in wheat requires a little more attention than you may be used to. However, a little more effort put into planning, scouting, product placement and application timing can pay great dividends.
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