Sidedressing Nitrogen for Nutrient Success

Categories: GROWING, CORN
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Due to being highly mobile in the soil, nitrogen (N) deficiencies are common in corn plants. If managed properly, appropriate N levels can result in substantial economic returns for farmers. However, with few opportunities to apply N last fall and this spring, many are reevaluating management plans. In case you didn’t have a chance to make a preemergence N application before your crop emerged, explore options still remaining. 


Corn plants with nitrogen deficiencies are light green or yellow-green, starting at the leaf tip and progressing down the midrib.

Application Timing and Use

Nitrogen mineralization from organic matter and prior season soybean residue can easily cover early growth stages N demand. Prior to V8, corn takes up less than 25 lbs. of N/A, but plants begin to rapidly uptake N by V6 growth stage. By silking, plants have absorbed near 70% of the total N they need. Yield potential can decline if N isn’t available during this critical window. Timely N applications in the form of sidedressing can help to manage any crop needs in larger corn.

Grass plants, such as corn, need maximum N availability prior to tassel and continue to use large amounts through seed fill. To accomplish this, apply N ahead of tassel to reduce the risk from earlier applications. Multiple application timings and good management practices are the best approach for success. Several universities provide N application timing research. The University of Illinois shows the impact of application types and timings across multiple years. Generally, it's best to split N applications between pre-plant and an in-season sidedress if a fall application wasn't possible. While sidedressing N is better than doing nothing, the University of Minnesota suggests sidedressing by V8 growth stage due to the role early N uptake has on yield potential. To maximize yield and enhance plant nutrient use efficiency, time application prior to peak uptake. 


Sidedress Application Options

  1. Anhydrous ammonia: A sidedress option that often requires larger field equipment for soil injections. Try to avoid leaf burn, especially on row ends when the toolbar picks up. The use of an N stabilizer is recommended when applying anhydrous ammonia.
  2. Urea (dry): Can be broadcast across top of emerged corn with a high clearance applicator at higher speeds to cover more acres per day. Consider using an N stabilizer with urea to minimize volitization losses since it will typically not be incorporated into the soil. Timing applications prior to rain events or row cultivation after application can also help minimize N loss with Urea.  Anticipate minor leaf burn from urea trapped with whorl of emerged corn.
  3. UAN (liquid): Can be broadcast sprayed, Injected into the soil or dribble between rows. If dribbling, use an N stabilizer since it requires rain to move into the soil. Broadcast applications can cause leaf burn, necrosis, and stunting. Broadcasting corn prior to V4 and applying at rates less than 60 lbs. of N/A can help minimize crop injury. Visible damage should disappear quickly with good growing conditions. Anticipate more severe injury at higher broadcast application rates and with bigger corn. Broadcast application to V7 or larger corn is not recommended, and sidedressing should be considered.


Source: International Plant Nutrition Institute – Corn Nutrient Uptake Patterns
Bender, Haegele, Ruffo and Below – Modern Corn Hybrids’ Nutrient Uptake Patterns, Better Crops, vol 97, 2013.

Evaluating Nitrogen Loss

Each season, farmers wonder about how much N they may have lost. But this question requires more questions to answer. Ask yourself what N sources you applied, when you made the applications, how was it applied, and what the weather (temperature and rainfall) conditions were since application.

Multiple methods can be used for assessing your current N status. Commonly used methods to evaluate N soil loss are described below:

  1. Soil sample method
  2. Crop sensors:
    1. Trimble® GreenSeeker® system
    2. OptRx® system
    3. CropSpec® system
  3. Nitrogen models

In summary, N and N stabilizers are greatly influenced by the environment, and there isn’t a magical formula to outline nutrient loss. Contact your Golden Harvest Seed Advisor with questions or for additional agronomic insights.

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