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Sidedress Time Approaches (06/02/16)

Corn in some areas is approaching V5 growth stage, which is the stage in which most side-dress N application should begin in this region.

Sidedress Time Approaches

Corn in some areas is approaching V5 growth stage, which is the stage in which most side-dress N application should begin in this region. In areas where rainfall has been low to modest, with no flooding rains, standing water, or in high clay soils, no continuously muddy conditions, the difference in corn N calculator values between what is recommended preplant and what was applied preplant should be a good rate. In soils with water issues, the rate should be higher. If you were wise and used a nitrogen-nonlimiting area as a standard when applying the preplant N application, and now will use an active-optical sensor to direct your sidedress, the sidedress rate will be directed by the active-sensor algorithm in the NDSU circular. If use of an active-sensor is not part of the side-dress strategy, educated guessing is required.  In a high-clay soil, any saturated muddy conditions results in about a 1.5% N loss per day. In a sandy soil with high (2 inch+) individual rainfall event or events, downward movement of N is likely, so increasing N rates by 20-40% depending on how much rain fell until the time of sidedress is probably a good estimate. If a nitrapyrin or DCD nitrification inhibitor or ESN® was used preplant, then losses in a high clay soil or in a sandy soil will be less. If Nutrisphere® or NZone®, which are not nitrification inhibitors, was used, then no modification of loss should be expected.

If the soil will allow, anhydrous ammonia can be used as a sidedress fertilizer. It can be applied to every other row. Apply at least 4 inches deep. Somewhere around 6 inches is a normal application depth. Consider (strongly consider) some kind of trench-covering tool to use on the applicator. I told a cooperator friend of mine 15 years ago that a covering tool would help his ammonia application, but he was reluctant to be the only farmer in North Dakota to use one I think. About 5 years ago, he decided to take my advice and put them on. He told me that he wished he had paid attention to me when I first suggested it. In high clay soils, a coulter UAN applicator can be used, with a coulter every-other-row, since the trench made by an anhydrous ammonia applicator will be resistant to closure even with a closing tool. A coulter UAN applicator can be used in other soils, and has the advantage of moving the UAN deep without additional rainfall in years where that may be a problem for surface applied N. For surface application options in our area, a drop tube down the middle between every row is just as effective as the y-drop option for side-dress N and is less expensive to set up. Both will perform similarly in our climate. The other alternative is urea over the top. Rates should not exceed 50 pounds N per acre, the urea should be treated with Agrotain® (or any NBPT containing brother or sister product at the proper a.i. per ton rate) or Limus® (NBPT + NPPT) to keep the urea safe from ammonia volatility for about 10 days.

In spring wheat, the best post-N treatment for yield is stream-bar applied UAN at 4 leaf to early jointing. N application after this growth stage may increase grain protein, but not yield. Post N treatment for barley is not recommended, unless the barley is designated as feed barley. The best time for N application for protein increase in wheat is immediately post-anthesis, not before or at heading regardless of the N product used.

Dave Franzen

NDSU Extension Soil Specialist

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