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Starter fertilizers and early-season nitrogen for wheat

 

by Stacy Campbellksu research and extension logo

K-State Research & Extension

 

To save time and cost, some wheat producers may be thinking about adding a little extra nitrogen (N) as urea or UAN to their phosphorus fertilizer through the drill with the seed. This would either be in addition to, or instead of, any preplant N applications.

While a minimum preplant N application of 20 to 40 lbs N per acre is often desirable, especially in no-till production systems, it is important to avoid placing urea containing fertilizers in direct seed contact. We suggest that NO urea or UAN solution be placed in contact with the seed. If the fertilizer N applied at seeding will be separated from seed by 1 inch or more, urea-containing fertilizers can be safely used.

Methods of early-season nitrogen applications

If the starter fertilizer can’t be “spiked” with urea to add extra N, how can the necessary 20 to 40 pounds of N be applied? Subsurface banding (knifing) of N as either anhydrous ammonia, liquid UAN, or dry product will result in the greatest N use efficiency by the wheat crop. This is especially true for no-till wheat production.

If knifed N applications are not used, the next best application method would be surface banding (dribbling) of UAN solution in streams on 15- to 18-inch centers. Broadcasting urea, ammonium nitrate, or UAN applications are not generally as efficient as subsurface banding, but they are often the best choice due to equipment, logistics, or weed management considerations. Broadcast applications of N will have the most consistent performance if followed by light incorporation, precipitation, or irrigation.

Direct seed placement of nitrogen

When placing starter fertilizer in direct contact with wheat seed, producers should use the following guidelines:

Suggested Maximum Rates of Fertilizer to be Applied Directly With Wheat Seed

 

Pounds N + K2O (No urea or UAN)

Row Spacing

(inches)

Medium to Fine

Textured Soils

Sandy or Dry

 Soils

15

16

11

10

24

17

6-8

30

21

 

The problem with placing urea-containing fertilizer with the seed is that urea is initially converted to ammonia and may be toxic to plant roots if the wheat seed is placed in direct contact with the fertilizer.

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