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ISSUE 7   June 14, 2001

 

TOP-DRESSING OPTIONS

A large number of fields were seeded this spring without any nitrogen fertilizer being applied beforehand. There are certainly questions about how to deal with fertilization of these acres. For any crops in 22 inch rows or wider, side-dress applications of ammonia, liquid, or cultivated in dry materials are standard methods which have a high degree of efficiency and are generally recommended in most years. The fertilizer should be placed between the rows as close to the middle centers as possible. Setting up the applicator to match the planter row widths and spacing will enable this to be done easily.

For solid-seeded crops, options are more difficult because of volatility issues with urea-based fertilizers. Dry urea may be applied when leaves are dry, to avoid leaf burn. Liquid fertilizers, such as 28% can also be used, but the burn potential is much greater. In a broadcast application, diluting the fertilizer with an equal volume of water will help reduce burn potential. Most small grain crops will respond positively to broadcast applications of N if diluted and the N is applied on a cool, cloudy day with wet foliage. Minimum leaf burn would be expected. However, broadcast liquid would not be recommended for broadleaf crops, except perhaps for canola after the waxy leaf surface has developed, usually after the 5 leaf stage. Another alternative to reduce burn potential in solid-seeded crops would be the use of straight-stream orifices instead of regular nozzles. These orifices are usually stainless steel discs with a calibrated hole in the center. They replace nozzles in the nozzle bodies and are selected based on gallons per acre, density of material and speed of the applicator. For general figuring, use a value of 1 gallon of 28% equals 3 lb N, and weighs about 10.6 lb/gallon. For exact numbers, contact your fertilizer supplier. The orifice spacing should be 15 inches apart at most. Apply at a slight angle to the row so that long row lengths will not come in contact with the fertilizer. Whatever plants do come in contact with the liquid fertilizer will be burned, sometimes severely.

The second concern is the volatility of urea in dry materials and in 28 %, which is about one-half urea. Rainfall of at least 1/4 inch must fall within 2 days of application this time of year for the full rate of N to be effective. If this does not appear likely, then adding the urea volatilization inhibitor Agrotain will allow the urea to remain on the surface another 10 days before volatility begins. It can be added to liquid fertilizers or it can be impregnated on dry urea. This should be done at the fertilizer dealership. Blending it in with a paddle at the farmstead is not a good idea.

Dr. Dave Franzen
NDSU Extension Soil Specialist
dfranzen@ndsuext.nodak.edu


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