May 15, 2003

 

Topdress Planning for Small Grains

Cool weather, good emergence, reasonable tillering and good soil moisture are making what looked like an iffy year for wheat production in the region appear very optimistic, according to Dave Franzen, North Dakota State University Extension Service soil specialist. "However, due to high nitrogen prices and conservative yield expectations, the nitrogen level in the field may be low compared to today’s yield prospects. Growers who want to take a chance on gaining higher yield potential may want to try topdressing their small grains."

Topdressing after the three-leaf stage will help increase the head size spikelet number and the kernel number. Hot and/or dry weather later on, particularly at the four-five-leaf stage and at pollination, will modify any improvements that the nitrogen additions make. Whatever topdressing strategy is employed, it must rain following application and before the six-leaf stage for it to be effective, according to Franzen.

Franzen recommends using liquid nitrogen such as urea ammonium nitrate (UAN), 28-0-0 and applied with streamer bars about the four-leaf stage. "Do not broadcast the UAN as the burn will be great and may cause a yield reduction in some cases. Streamer bars concentrate the application into bands which tend to drive most of the fertilizer to the soil surface rather than coat the leaves where it could damage leaf tissue."

A concentrated band also slows the rate of urea volatilization from the urea portion of the UAN. The nitrogen in UAN is approximately 50 percent urea. The ammonium nitrate half of the UAN solution is not subject to volatilization, making UAN a preferred fertilizer over dry urea for this type of application.

Streamer bar application is most effective when used on calm days. The danger of burn increases as the wind increases. Under windy conditions, the wind breaks the stream apart and converts it into a poor broadcast application by coating leaves and increasing burn.

"If dry urea is used, it might be wise to have it coated with Agritain," according to Franzen. "Agritain is a tested, tried and proven urease inhibitor and gives about 10 days of protection from volatility."

Whatever source is used, rain is required to move the nitrogen into the soil. About a quarter inch of rain is need on bare soil. More rain is needed on fields that have residue, particularly if there is a thatch cover. Yields will not be enhanced if it does not rain until after the six-leaf stage.

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Source: Dave Franzen, (701) 231-8884, dfranzen@ndsuext.nodak.edu
Editor: Rich Mattern, (701) 231-6136, richard.mattern@ndsu.nodak.edu