By ANGELA RIECK-HINZ
Nitrogen management is always a hot topic both from an agronomic, as well as an environmental standpoint. We should recognize that nitrogen management such as timing of application is important, but nitrogen timing alone won’t solve all agronomic or water quality issues. Let’s take a look at sidedressing as one method of nitrogen application.
Sidedressing takes place once the corn has been planted. Farmers may choose to apply all of their nitrogen at sidedress time, or they may use that timing as a second application of nitrogen after a less than full rate was applied in the fall or at preplant. Split application is often suggested, especially in continuous corn, so the crop is not short of nitrogen until sidedress nitrogen is applied and becomes available to plants.
Sidedress application can improve corn nitrogen use, but only if the sidedress timing misses loss conditions that would have impacted nitrate from preplant conditions. In some situations, if significant loss of nitrogen is suspected, farmers may need to consider sidedressing nitrogen in addition to a full rate already applied, as a rescue treatment for the crop.
Factors to consider
If you choose to sidedress nitrogen, keep these factors in mind:
• Nitrogen source. Different nitrogen sources are included in the table below, and farmers should recognize the properties of each product and how application and potential for loss may influence decisions on which product to use.
• Application rate. Plan to account for all sources of nitrogen applied prior to sidedress application when determining sidedress application rate. These would include fall anhydrous, manure applications, spring preplant nitrogen and any nitrogen included in MAP, DAP or as a herbicide carrier. If sidedress application is being done as a rescue treatment due to nitrogen loss, then you may need to use the Late Spring Nitrate Test (LSNT), or crop-sensing equipment to determine an appropriate application rate.
• Availability of products and equipment. If your normal routine is to sidedress nitrogen, then likely you have planned for the products and needed equipment. If more farmers choose to move from fall-applied anhydrous to spring-applied nitrogen such as urea, or UAN, to address timing from a water quality concern, we may see pressure put on fertilizer distribution, storage needs and equipment availability. If rescue treatments are needed, access to both products and equipment may be a challenge. In either case, work with your fertilizer retailer to ensure availability of product and equipment.
• Rainfall makes a difference. If side-dressing is done as part of the normal operation to better time your nitrogen application with a growing crop, it will be important that the nitrogen applied can be in the root zone for crop uptake. This will be done during application (injection or incorporation) or will be done with rainfall. If possible, try to time the application prior to rainfall. This helps move the nitrogen into the root zone, and reduces opportunity for volatile losses from urea.
Rieck-Hinz is the ISU Extension field agronomist for north-central Iowa. Contact her at firstname.lastname@example.org.
• For more information, visit the ISU Extension soil fertility website at www.agronext.iastate.edu/soilfertility.
Nitrogen products and sidedressing
Dry ammonium nitrate
or ammonium sulfate
Must be injected. Late
application difficult due to crop interference with
Broadcast, surface-banded, or band-injected. Incorporated with row cultivation or left on soil surface. Late application with high-clearance equipment.
Injected, dribbled as a band,
or broadcast. High clearance equipment can dribble solution onto soil surface or shallow inject.
Same as urea.
When left on soil surface can be subject to volatile loss if no rain received after application. May need a urease inhibitor product.
Because half is urea
(half ammonium nitrate),
volatilization is a concern when left on the soil surface. Surface banding reduces volatile loss.
Ammonium nitrate and
ammonium sulfate are less
susceptible to volatilization (slight potential on calcareous soils with high surface pH).
If depth is not adequate during application, ammonia loss from the soil may cause cosmetic leaf tissue burn.
Broadcasting over growing corn may cause leaf spotting or edge browning. Typically, that injury does not influence yield.
Broadcast across growing corn can cause leaf burn and reduced early growth. Injury is related to rate of UAN and crop stage. Broadcast application after the V7 growth stage is not recommended. Hot and dry conditions
will increase chance of injury.
Broadcast over growing
corn may cause leaf spotting
or edge browning. Damage is typically more than occurs
This article published in the May, 2015 edition of WALLACES FARMER.
All rights reserved. Copyright Farm Progress Cos. 2015.